Pathogenesis and Management of Cardiogenic Shock and Postoperative Shock. Introduction. Chest 1992

8/10/2019 Pathogenesis and Management of Cardiogenic Shock and Postoperative Shock. Introduction. Chest 1992

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* From the Research and Congestive H eart Failure Divisions,

M inneapolis H eart Institute Foundation, M inneapolis.Reprint requests: D r.Goldenberg, M inneapolis H eart Institute, 92 0East 28th Street, M inneapolis 55407

596S M anagem ent of Cardiac Arrest and C ardiogenic S hock Irvin F G o ld e nb e rg

N on pharm aco lo g ic M anag em ent o f C ard iac A rres t an dC ardiogenic Shock*Irvin F . G oldenberg, M.D. F.C.C.P

P harm acologic m anagem ent of patients w ith cardiacarrest or cardiogenic shock m ay be insuIcient in

restoring adequate circulatory support. This has led

physicians to investigate and develop m ore aggressive

interventions for these problem s. Cardiogenic shock

m ost frequently occurs in the follow ing clinical set-

tings: (1) acute m yocardial infarction; (2) postcardiot-

om y; (3) an acute exacerbation in som eone w ith chronic

cardiac dysfunction and congestive heart failure; (4)

cardiac arrest secondary to an arrhythm ia; (5) cardiac

dysfunction secondary to a com plication from a per-

cutaneous interventional cardiac procedure,eg , coro-

nary angioplasty; and (6) less often as other acute

illnesses, eg , m yocarditis. A lthough initia l m anage-

m ent often requires im m ediate intervention to restore

circulatory support, even prior to know ing the defini-

tive cause of the patients shock,it is im portant that

an extensive diagnostic evaluation, particularly pur-

suing reversible causes of shock, be undertaken at the

earliest possible tim e. D uring this evaluation,it is

im portant to determ ine the degree of both left and

right ventricular dysfunction, as interventions m ay

differ particularly w hen m echanical circulatory assist

devices are being considered.

D espite recent pharm acologic advances, w hich have

led to the developm ent of newer inotropic agents (eg,

am rinone) and to throm bolytic therapy, recent studies

have dem onstrated that the incidence and m ortality

of cardiogenic shock in patients w ith an acute m yocar-

dial infarction, treated predom inantly w ith m edical

therapy, have not changed significantly over a recent

13-year period. The inhospita l m ortality rate in

patients with acute m yocardial infarction and cardio-

genic shock, treated predom inantly w ith pharm aco-

logic agents , has been reported to be between 70 and

1 00 p erc ent. - Even w hen pharm acologic therapy is

able to provide adequate circulatory support, m any

patients m ay still need a nonphannacologic interven-

tion eg , coronary artery bypass surgery to reverse

ischem ia) to restore adequate cardiac function andtherefore allow one to be weaned from pharm acologic

therapy.

Nonpharm acologic treatm ent for cardiogenic shock

and cardiac arrest consis t of (1) interventions eg ,

m echanical circulatory assist devices, cardiac trans-

plantation) that provide circulatory support to the

patient no m atter what the underlying cause of thecirculatory deterioration, and to (2) interventions eg ,

percutaneous interventional or surgical corrective pro-

cedures) that correct or reverse the specific cause of

the underlying shock (Table 1). This artic le will discuss

the nonpharm acologic interventions that have been

helpful in restoring circulatory support and reversing

underlying causes of cardiogenic shock and cardiac

arrest. These nonpharm acologic interventions have

had a significant im pact on the survival of these

patients. Tables 1 and 2 list the various m echanical

circulatory assist devices and cardiac procedures that

have been used in patients w ith cardiogenic shock.

Patients with cardiogenic shock or cardiac arrest

w ho require nonpharm acologic intervention generally

fall into three categories:

1.Patients Requiring Tem porary M echanical

C irculatory Support Only

These patients have cardiac dysfunction that is

expected to im prove w hile their circulation is sup-

ported by nonpharm acologic interventions (eg, m e-

chanical circulatory assist devices). Som e patients w ith

postcardiotom y cardiogenic shock would fall in this

category. These patients are often believed to have

stunned m yocardium that w ill recover with tim e.

2. Patients Requiring Tem porary C ircula tory Support

and a Circula tory or Cardiac Corrective P rocedure

Patients w ho require em ergent circulatory support

(,pharm acologic and/or m echanical circulatory assist

devices) and also have a circulatory or cardiac disorder

requiring a nonpharm acologic intervention eg , per-

cutaneous interventional or surgical procedure) to

restore cardiac function fall in this category. Even

after the nonpharm acologic intervention eg , coronary

angioplasty, coronary artery bypass surgery) has been

perform ed, these patients m ay require prolonged

circulatory support while their underlying cardiacfunction m ore fully recovers. Patients with acute

m yocardial infarction and cardiogenic shock requiring

percutaneous or surgical revascularization would fall

in this category.

3. Patients W ith Irreversible Cardiac D ysfunction

who Require Cardiac Transplantation or aPermanent

Im plantation of a M echanical Assist D evice

Patients w ho are in cardiogenic shock and w hose

wnloaded From: http://journal.publications.chestnet.org/ by a University of Minnesota Libraries User on 07/19/2014


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C H E S T I 10 2 I 5 I N O V E M B E R 1992 I S upplem ent 2 597$

Table -Nonpharsnacologic Managemen* of

Cardiogenic Shock

M anagem ent of Shock

M echanical ventila tion

Mechanical circulatory a ss is t d ev ic es

Intra-aortic balloon p u m p

Pulm onary artery balloon counterpulsation

Extracorporeal membrane oxygenation*

Percutaneous left atria l to femoral artery bypassH e m o p u m p t

Left ventricular assist device or system

Right ventricular assist device

B iventricular assist devices

D irect m echanical ventricular actuation

Total a rt if ic ia l h ea rtPercutaneous interventional procedures and nonsurgical treatment

of cardiogenic shock or cardiac arrest

Percutaneous m echanical revascularization (coronary angioplasty,

directional an d rotational atherectomy, coronary laser angio-

plast coronary stunting, an d other m echanical percutaneous

interventions tha t attem pt to perm anently restore coronary

blood f low)

Augm entation of distal coronary blood flow (tem porary augm en-

tation)

augm entation of antegrade coronary perfusion by passive or

active antegrade coronary perfusion methods e g perfusion

or bailout catheters)

Synchronized coronary sinus retroperfusion

Valvuloplasty

Percutaneous transcatheter closure of ventricular septaldefect

Pacemaker for optim al h ear t ra te and atrioventricular delay

control

C atheter or ch em ical ablation ofarrhythmias

Pericardiocentesis

M echan ical circulatory ass ist d evices

Intra-aortic balloon p u m p

Percutaneous cardiopulm onary support*

H e m o p u m p t

Percutaneous left a tria l to femoral artery bypass

C ardioversion or defibrillationS urgic al p roc edu res

Coronary artery bypass grafting

Valve repa ir o r r ep l ac e m en t

Cardiac rupture repair (ventricular septal defect, free wall)

Pericardiectomy

Aneurysm ectom y for aneurysm responsible for intractable ar-

rhythm ias and/or card iogenic sh ock

P ulm onary em bolectom y

Pericardial w indow

Rem oval of intracardiac or extrinsic cardiac m ass contributing to

cardiogenic shock (eg, atria l myxoma)

Surgical treatm ent of arrhythmias e g ablation, subendocardial

resection)

Pacemaker for optimal heart rate and atrioventricular delay

controlM echanical circulatory assist devices (see above)

C oronary s inu s retroperfusion

Cardiac transplantation (orthotopic, heterotopic, and xenograft)

*May be p lac ed pe rcu tan eou sly or by surg ica l c utd ow n.

tPercutaneous device being developed.

cardiac function is believed to be irreversibly dam aged

fall into this category. These patients are initia lly

supported w ith pharm acologic agents and/or m echan-

ical circulatory assist devices. Cardiac transplantation

is usually the treatm ent of choice in acceptable

candidates. H ow ever, in patients not considered can-

didates for cardiac transplantation, perm anent im plan-

tation of a m echanical assis t device has been tried.5

W ith the developm ent of newer, im proved perm anent

m echanical circulatory assis t devices, the num ber of

patients falling into this la tter category hopefully w ill

increase in the near future.

It is not alw ays possible to determ ine which categorya patient m ay fall into because it is often difficult to

determ ine whether cardiac dysfunction is perm anent

or reversible. O ne patient was supported for 70 days

w ith a left ventricular assist device (LVA D ) w ith the

intent to perform cardiac transplantation.6 H ow ever,

the patients left ventricular function im proved signif-

icantly, m aking transplantation unnecessary.16

M EC H A N IC A L V E N T IL A T IO N

Initia tion of m echanical ventila tory support m ay

signfficantly im prove a patients system ic hem odynam -

ics by elim inating the w ork of ventila tion. T his can

provide as m uch as a 1-L increase in effective cardiac

output in som e patients, thus elim inating the need for

m echanical circulatory support in the occasional pa-

tient.

M E C H A N IC A L C IR C U L A T O R Y SU PP O R T D EV IC ES

The prim ary functions of m echanical circulatory

assist devices are (1) to provide circulatory support

and (2) to assist in m yocardial recovery.1 The prin-

cipal purpose in m ost patients is usually to provide

adequate circulatory support that is suffic ient to per-

fuse the vita l organs and prevent irreversible dam age.

To assist in m yocardial function recovery, m any of

these devices produce ventricular unloading, dim inish

m yocardial w ork, and favorably alter the ratio of

m yocardial oxygen supply and dem and. W hen consid-

ering w hich device to use in an individual patient,it

is im portant to understand the degree of circulatory

support (partia l or com plete) and the level of m yocar-

dial protection each device can provide.

H em odynam ic indications for m echanical circula-

tory support beyond the use of the intra-aortic balloon

pum p (IA BP) for patients with cardiogenic shock have

often been based on the suggestions of N orm an and

associates.as These suggestions, show n in Table 3, w ere

initially supported by m any investigators; how ever,

they are now believed to perhaps be too stringent and

probably harm ful if followed too rigidly.89 It has been

reported that the earlier the intervention w ith circu-

latory support devices, the better the outcom e.

Although prolonged use of high-dose inotropic therapy

m ay be able to provide borderline hem odynam ics and

m arginal circulatory support, prolonged use of these

agents m ay lead to increased m yocardial w ork and

potentia lly irreversible m yocardial dysfunction. In



3/21

on th e w ork of N orm an et ale and rep rin ted w it h p erm iss io n

from P en nin gton D G , Swartz M T.8

Table 2-Guidel ines fo r A pp ro pr ia te Selection of Mechanical Circu latory Support Devices

598S Management of C ardiac Arres t and C ardlogenic S hock Irvin F Goldenberg)

I)evice

Investi-

gational Pusition Support

Anticoagulation

Required

Preferred

Application Duration

Pulsalile

F low M echanism

Flow,

Umin

U su al M od e

Insertion

U su al S ite

Insertion

tA RP N o Internal L M oderate K , F B-Tx Short-inter Y esPN Pulsatile 0.5-0.8 Per, S FA

PARC N o Internal K Low P Short-inter Y es PN Pulsatile - St PA

Sarns& obe No ExtracorporealRt , L, B Full P , B-Tx S hort-in ter N o R O L L 6.0 S R APA, L AA o,LVA o

R ol le r P um p

Electrocatheter Y es Extracorporeal L Full K , P Short No CEN T,R O L L 1.5-4.5 Per F FA

Bin M edicus N o ExtracorporealRt , L, B Low -m oderate P ,B-Tx S hort-in ter No CEN T 5 S RA PA , LAA oLVAo

Centrim ed/Sarns No Extracorporeal Rt, L , B Low -m oderate P B-Tx Short-inter NoCEN T 5 S RA PA , LA Ao,

LVAo

ECM O N o Extracorporeal B Full K Short No CEN T, ROLL5 Per, S FsFA

H em opump Y es Internal L M oderate B, P Short No Rotary 3.5 St FA

Abiom ed BVS Y es Extracorporeal R t, L , B M oderate F, B-Tx Short-interYes PN Pulsatile 6.5 5 RA PA , LA Ao

Pierce-Donachy Y es Faracorporeal R t, L , B Low P B-TI Short-long Yes PN P ulsatile 6 S RA PA , LAA

VA D(Fhoratec)P ierce-Donachy Y es F aracorp oreal R I, L, B L ow F B-Tx Short-long Yes PN Pulsatile 6 5 RA PA , LA Ao,

VA D(Saran) LVA oSym bio n AVA D Yes Pararorporeal R t, L, B M oderate F, B-Tx Short-long Yes PN Pulsatile 7 5 RA PA , L A AoNovaror LVAs Yes Internal L Low B-Tx Short-long Yes EL Pulsatile 10 S LV AoThermedics VA D Yes Interim ] L N one B-Tx Short-long Yes PN P ulsatile 10 S LVAo(I -Heartmate)

S ym bio n TA ll Ye s Internal B M oderate B-Tx Short-long Y es P N Pu lsa tile 10 5 R AP A, L AA o

D M VA Ye s Internal B N one B,B -T x, P Shor t Yes PN Pulsatile 80-110%

of control

5

n vestiga ti.o na l de sic e exe mp tion requ ired fro m F ood and D rug A dm inistra tion . B VS =biv entricu lar sup po rt system ; E CM O =e xtra co rpo real m em brane o xy gen ation;LVAS=lef t ventricular

L =l ef t; B= bi ve nt ri ru la r; R =r es us ci ta hv, P=postcardiotomy;

B -Tx=bridge-to-transplantation; JA BP=intra-aortic balloon pum p; P AB Cpalm onary artery balloon counterpulsation; E lectsocatheter= percutaneous left atrium

bypass. P er=percutaneous; S =surgjcal procedure; RA PA = right atrial and pulm onary artery; L& Ao=left a trium and aortic ;LVAo= le ft ven tricle a nd a orta ; P A= pulm onary artery ;

F A= fem oral a rtery; F V= fem ora l ve in; ln ter= in term edia te; P N= pn eum atic;EL ele ctrical; C EN T= ce ntrifug al; R OL L= roller pu mp .

tP erc uta neo us ap pro ach being de velope d. M odified an d printed w ith pe rm issio n h umrefurenoes 18,20, and 21.

addition, prolonged m arginal circulatory support,

even if it m eets the criteria in Table 3, m ay lead to

irreversible dysfunction of other organs. Therefore ,

consideration for device im plantation should be m ade

prior to prolonged support w ith high doses of inotropic

agents. The hem odynam ic indications for circulatory

support devices outlined in Table 3, therefore , w hile

helpful, should be considered only guidelines.

W hen selecting a device,it is im portant to evaluate

the follow ing: (1) the potential reversibility of the

cardiac dysfunction; (2) the cause of the cardiac

dysfunction; (3) the degree of right and left ventricular

dysfunction; (4) the degree of circulatory support

Table 3-Hemodynamic Guidelines fo r M ec ha nic alCirculatory Support5

Guidelines

Cardiac in dex


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C H E S T I 10 2 I 5 I N O V E M B E R 1992 I S upplem ent 2 599S

Table 4-C riteria for tlniventricular and

R iventricular Support5

Criteria

Bight ven tr icu lar fa ilu re: R V A Dan d IABP

LA P 20 m m H g

Few or no arrhythmias

Near norm al left ventricular function by echo, cath, or M U GA

Left ventricular failure: LVA D onlyLA P >20 mm Hg

RA P 20 mm Hg

V entricular tachycardia or fibrilla tion

Severely im paired left and right ventricular function by echo,

cath, or M U G A

5 RVA D = right ventricular assist device; IA BP= intra-aortic balloon

p u m p ; RA P=right atrial pressure; LA P1eft atria l pressure;

LVA D = left ventricular assist device; echo= echocardiography;

B VA D s = b iventr icu lar assist devices; cath= catheterization;

M U G A = m ultigated acqu isition scan.Printed w ith perm issionfrom Penn ington , e tal.25

ventricular failure , an LV A D only; for right ventricular

failure a right ventricular assist device (RV A D) and an

IA BP If both ventric les w ere contracting poorly and

both right and left a tria l pressures w ere greater than

20 m m Hg, both an LV A D and an RVA D w ere

im planted. W hen arrhythm ias producing significant

hem odynam ic com prom ise w ere present, support

w ith biventncular assist device (BV A D) was favored.as

M echanical circulatory support devices m ay be

classified by m any different m ethods, and at present,

there is no universally accepted classffication. D evices

have been classified by the following: (1) their intended

use, ie , resuscitation or long-term support; (2) the

m echanism by w hich they provide circulatory support:

centrifugal, rotary, pneum atic pulsatile , and electric

pulsatile ; and (3) their position: extracorporeal, para-

corporeal, heterotopic (internal or external), or ortho-

topic .ss.sa Only a few of the presently used m echanical

assis t devices are universally available w ith m ost being

investigational and requiring Food and D rug Adm in-

is tra tion (FD A) approval. Table 2 lists the various

approved and investigational m echanical circulatory

assis t devices and provides the various characteristics

of the individual devices .1 For this review , I haveelected to classify devices in a m anner slightly differ-

ent from but sim ilar to that reported by Pennington

and Sw artz .8 D evices are classified as resuscita tive,

external centrifugal and roller pum ps, external pulsa-

tile assist devices, im plantable LVA D s, pulm onary

artery balloon counterpulsation, orthotopic biventric-

ular replacem ent prosthesis (total artific ial heart), and

perm anent devices. 18

The clinical results provided in this artic le are from

m ultiple sources, and include the volunteer regis try

for m echanical assist devices and artific ia l hearts at

Penn State University under the auspices of the

A m erican Society of Artific ia l O rgans (A SAIO ) and

the International Society for H eart Transplantation

(ISHT), the Total A rtific ia l H eart Registry at the

M inneapolis H eart Institute , the N ational R egistry for

Em ergent Percutaneous C ardiopulm onary Bypass , de-

vice m anufacturers , investigators, and literature re-view

Resuscitative Devices

Resuscita tive devices are m echanical circulatory

support devices that can be placed rapidly and do not

require an operating room for insertion. These devices

are often inserted in the em ergency departm ent,

intensive care unit, and cardiac catheterization labo-

ratory.8 The resuscita tive devices include the IAB P,

extracorporeal m em brane oxygenation (ECM O ), a

percutaneous left a tria l fem oral artery bypass system ,

a continuous axial blood flow pum p (Hem opum p), and

direct m echanical ventricular actuation (D M V A ). M ost

of these devices are usually placed for short-term use,

and if prolonged circulatory support is needed, the

patient usually is sw itched to one of the devices m ore

suitable for long-term support (Table 2).

The IAB P is the sim plest, m ost com m only used

m echanical circulatory assist device. A pproxim ately

75,000 to 80,000 IA BPs are inserted each year in the

U nited States (personal com m unications, DataScope

Corporation, M ontvale, N J). The exact num ber being

placed because of cardiogenic shock and cardiac arrest

is not known, how ever. The IA BP is usually inserted

percutaneously, and less often by cut-dow n, into the

fem oral artery and advanced into the descending

thoracic aorta just distal to the left subclavian artery.

W hen fem oral artery access is not possible , the balloon

catheter m ay be advanced into the descending thoracic

aorta from the iliac artery, axillary artery, subclavian

artery, abdom inal aorta , and ascending aorta .an In

addition, w hen long-term support with this device is

planned, it has been suggested that the patient can

be m obilized easier if the catheter is inserted in the

(1) axillary artery, (2) subclavian artery,sa or (3) iliac

artery.4 W hen placed in the iliac artery as a perm a-

nent device, the extravascular portion of the balloon

pneum atic tubing was stabilized by routingit

throughthe iliac crest.4

The IA BP is a pulsatile , pneum atic device that

infla tes with gas during diastole and deflates during

systole.#{176} The balloon catheter produces a reduction

in left ventricular afterload and an increase in coronary

perfusion pressure along w ith a decrease in m yocardial

oxygen consum ption, w hich favorably alters the ratio

of m yocardial oxygen supply and dem and.# {1 76 } A lt ho ug h

the device increases coronary diastolic perfusion pres-



5/21

600S Management of Cardiac A rres t and Cardiogenk S hock Irvin F Gokienberg)

Table 5-H em odynam ic Effectsof Intra-aort icBalloon Pump

Effects % Change

Peak systolic arterial pressure 5 -1 5 d ec re ase

P resystolic (end -diastolic) aortic 2 0-3 0 d ecr ea se

pressure

Diastolic aortic pressure 70 increase

M ean aortic pressure N o significant change

Left ven tricular en d-d ias tolic pressure 10-20 d ecreasePulm onary artery w edge pressure 1 0- 20 d ec re ase

P eak d is/c lt 1 0- 20 d ec re as e

Heart rate 5-10 decrease

V m ax 25 decrease

Cardiac output 10-41) increase

sure, the ability of this device to increase coronary

blood flow in patients w ith severe flow-lim iting coro-

nary disease has been questioned. How ever, it does

appear to often increase coronary blood flow in

patients w ith m oderate to severe hypotension and

cardiogenic shock. {149}

The hem odynam ic effects of this device are variable

and depend som ewhat on the underlying cardiacfunction,29 The cardiac output m ay typically increase

from 10 to 40 percent (usually 10 to 20 percent).829

A lthough augm entation of cardiac output by 500 to

800 m I/m m has been reported to be the average

patient response, som e patients m ay have very m ini-

m al response w hile others m ay have significant

increases in cardiac output ie , >1.5 L/m in in-

crease). 19.29.33,34 The left ventricular end-diastolic pres-

sure and pulm onary artery w edge pressure usually

decrease 10 to 20 percent, but decreases >30 percent

have been seen in som e studies.29-33 The typical

hem odynam ic changes that occur w ith IA BP insertion

are show n in Table5,29

A lthough the IA BP is usually inserted for a short-

to interm ediate-term duration, the device has been

used for long-term support. O ne patient w as sup-

ported for 327 days.33 The IA BP has been used for

cardiogenic shock and cardiac arrest. W hen used for

cardiogenic shock secondary to a m yocardial infarc-

tion, this device has produced conflicting reports

regarding its ability to affect m ortality when used

without revascularization procedures.133 3.b 0 A c lo se

review of the data , how ever, does suggest the IA BP

has a m odest effect on decreasing m nhospita l m ortality

from cardiogenic shock in acute m yocardial infarction,

but long-term m ortality and m orbidity continue to be

poor. W hen this device is used alone (w ithout

revascularization) in patients w ith m yocardial infarc-

tion and cardiogenic shock, short-term (inhospital or

30-day) m ortality is betw een 47 percent and 83

percent.3340 M any of these patients m ay becom e

balloon dependent, w hile other patients m ay require

prolonged circulatory support eg , >14 days) before

they are able to be w eaned from the device.333740-

H ow ever, when the IA BP w as used in conjunction

w ith surgical revascularization for patients w ith acute

m yocardial infarction and cardiogenic shock, inhos-

pita l m ortality and long-term survival w ere im proved

when com pared w ith treatm ent w ith an IA BP

alone

W hen used early, an IA BP can potentia lly assis t in

m yocardial recovery. This device is very effective in

patients w ith acute m yocardial infarction and severem itral regurgitation or ventricular septal defect.30- It

also has been effective in treating hem odynam ically

unstable refractory ventricular arrhythm ias presum a-

bly by favorably im proving the ratio of m yocardial

oxygen supply and dem and and by im proving system ic

hemodynamics.#{176}-47

The IA BP has been used successfully as the sole

nonpharm acologic intervention in postcardiotom y

cardiogenic shock, w ith m ortality rates between 37

percent and 73 percent.8-33-5 In addition, the IAB P

was am ong the first m echanical assist devices used

successfully as a bridge to transplantation.52 Posttrans-

plant survival in patients who receive an IAB P as a

bridge to transplant is sim ilar to patients w ho w ere

supported w ith pharm acologic agents alone prior to

transplantation. A lthough the IA BP is capable of

supporting the circulation in som e patients, the m ajor

disadvantages are its relatively m inor effect on hem o-

dynam ics com pared w ith other m echanical assist de-

vices and its inability to have a significant effect in

m any patients w ith severe right ventricular dysfunc-

tion. Patients with the m ost severe cardiogenic shock

and patients in cardiac arrest will, in general, need

devices capable of providing a greater degree of

circulatory support. Low to m oderate to full dose

heparinization is usually used w ith the IABP C om pli-

cations occur in up to 30 percent of patients with

IAB E Com plications are prim arily vascular, but also

include infection, hem olysis, throm bocytopenia , em -

bolization, and gas leak. Contraindications include

significant aortic insufficiency and a significant aortic

aneurysm . The device m ay have difficulty functioning

adequately w hen cardiac arrhythm ias are present.

Fem oral artery-fem oral vein ECM O provides rapid

cardiopulm onary bypass for patients w ith cardiogenic

shock and/or cardiac arrest.8 A lthough original

placem ent of fem oral-fem oral ECM O required surgi-

cal cut-dow n, it now is frequently placed percutane-

ously.M The percutaneous technique w as initia lly

described by Phillips et al in 1983. Because of

advances in catheter design and favorable results from

the N ational R egistry of E lective Supported Angio-

plasty, use of this technique has led to rapid acceptance

of this approach for em ergency circulatory support.

Fem oral-fem oral ECM O has also been referred to as

peripheral cardiopulm onary bypass and when placed

percutaneously, percutaneous cardiopulm onary by-



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C HE S T 1102 I 5 I N O V E M B E R 1992 I Supplem ent 2 601S

pass. The system consists of a venous and arterial

cannula , a m em brane oxygenator, a blood pum p, and

a heat exchanger.34 The venous cannula is inserted

into the fem oral vein and advanced to the inferior

vena cava or right atrium . The arterial cannula is

inserted in the fem oral artery and m ay be advanced

into the iliac artery or aorta . B lood is withdraw n from

the right atrium or inferior vena cava through the

venous cannula and into the blood pum p (m ost oftena centrifugal blood pum p), where the blood is then

pum ped to the m em brane oxygenator and the blood

becom es oxygenated. The oxygenated blood then

returns through the arteria l cannula to the patient.

A lthough ECM O has been used to support patients

for up to 18 days,33 it is presently recom m ended that

patients who require continuous support for m ore

than 48 h have alternative m echanical circulatory

devices pursued for im plantation.18 A t experienced

centers, percutaneous cardiopulm onary support can

often be established w ithin 15 m m . The Volunteer

National Registry of Supported A ngioplasty Partic i-

pants is also collecting data on em ergency peripheral

cardiopulm onary bypass.57 The registry presently has

data on 234 patients w ho w ere treated w ith em ergency

peripheral cardiopulm onary bypass due to cardiac

arrest (N= 168) or cardiogenic shock (N= 66). There

w ere 82 patients (35 percent) w ho survived and were

im proved at the tim e of hospita l discharge. Patients

w ho had cardiopulm onary bypass established in less

than 20 m m had a 50 percent inhospita l survival. Flow

rates w ith this device are usually betw een 3.5 and 5

L/m in in m ost patients.34 Patients require full hepa-

rinization.8 How ever, there has been a report of safely

using ECM O without heparin in four patients w ho

had severe hem orrhage.29 D espite this report, full

heparinization is recom m ended. Com plications from

this device include bleeding, biventricular failure ,

infection, neurologic deficits, throm boem bolic events,

and lim b ischem ia. 33 Com pared with other m echan-

ical circulatory devices, patients on ECM O are less

m obile than the paracorporeal pneum atic devices, and

have longer and m ore severe hem olysis than the

noncentrifugal V A D.33 Its m ajor advantages are its

rapid insertion and its com plete cardiopulm onary

support even in patients w ith arrhythm ias, such asasystole or ventricular fibrilla tion. A lthough this de-

vice has been dem onstrated to provide excellent

system ic perfusion and hem odynam ic support, its

ability to provide m yocardial protection is un-

clear.18,60,65 In fact, there are data to suggest that

percutaneous cardiopulm onary support can induce

cardiac anaerobic m etabolism resulting in a detrim en-

tal effect on m yocardial protection.6 A dditional stud-

ies have dem onstrated regional wall m otion abnor-

m alities w ith w orsening w all m otion scores during

cardiopulm onary-supported coronary angioplasty.6#{176}

A percutaneous left a tria l fem oral artery circulatory

support system that obtains access to the left a trium

with a transseptal puncture has been used to success-

fully resuscitate patients in cardiogenic shock.as This

percutaneous partia l left heart bypass system uses a

14 to 20 French specifically designed venous cannula

(Electrocatheter Corporation, Rahw ay, N J, or Schnei-

der U SA , M inneapolis, M inn), w hich is inserted into

the fem oral vein and advanced across the intra-atria l

septum after a transseptal puncture is perform ed.62

Blood is then w ithdraw n using a roller pum p from the

left a trium and returned through a 14 to 20 French

cannula that has been inserted into a fem oral artery

and often advanced into the iliac artery or aorta . Since

a transseptal puncture is perform ed, this procedure

m ust be done under fluoroscopy. Flow rates of 1.5 to

Ficure 1. The Hem opum p is inserted into the com mon

fem oral artery vi a side arm graft an d is advanced acrossth e aortic valve into th e left ven tricle (reprodu ced w ith

perm ission from E m ery andJoyce).



7/21

F I G U R E 2. The A rchim edean screw is approximately the size of a

pencil (reproduced w ith perm ission from Emery and Joyce).

SUS TA INE D NEG ATIVE

PR ESSU R E SYSTE M

VACU U M SO U R CE

D AM PER VALVE

F I G U R E 3. The schematic diagram of the direct m echanical ventricular actuation drive system and cup.The cup is show n actuating the ventric les into both the systolic right) a nd d ia sto lic left) configurations

(reproduced w ith perm ission from Low e et al .

602S M anagem ent of Cardiac A rrest and C ardiogenic S hock Irvin F Goldenberg)

4.5 L/m in have been obtained.62 Patients have been

supported w ith this device for up to 10 days.62 O nly a

sm all num ber of patients w ith cardiogenic shock have

received this device.627 C ontinuous and full hepa-

rinization is recom mended.8

The H em opum p (Johnson & Johnson, W arren, N J)

is a new , continuous axial blood flow pum p (Fig 1) that

propels blood from the left ventric le to the descending

aorta.672 It is an intravascular pum p that uses an

A rchim edean screw principle (Fig 2) and rotates at

15,000 to 25,000 rpm to provide unidirectional, non-

pulsatile flow at rates of 2 to 3.5 Lfm in. The 21 French

size pum p and inflow cannula of the Hem opum p is

advanced through a surgical cut-dow n in a fem oral

artery. The flexible 7-m m inflow cannula of the cable-

driven pum p is then advanced under fluoroscopic

exam ination into the ascending aorta and then across

the aortic valve into the left ventric le . The cable drive

shaft of the Hem opum p is 11 French and rem ains the

only obstruction to com m on fem oral artery flow

O ccasionally, insertion is m ade through the aorta . A

shorter H em opum p for direct insertion via the as-cending aorta is under developm ent. The H em opum p

is useful only for left ventricular support. A recent

s tudy of the H em opum p in patients w ith cardiogenic

shock w as com pleted (Johnson & Johnson sum m ary

report on m ulticenter trial w ith H em opum p in cardi-

ogenic shock: unpublished data). O ne hundred tw enty-

three patients w ho w ere supported for up to 14 days

w ere entered into this study. N inety-seven patients

(79 percent) underwent successful insertion of the

H em opum p while 26 patients (21 percent) were unable

to have the H em opum p inserted. N ine patients w ho

received the H em opum p were excluded from analysis

because they also had received other cardiac assist

devices. In the 88 patients still analyzed, 24 (27

percent) survived. In the 26 patients in w hom the

H em opum p could not be inserted, there were 5 (19

percent) survivors. The lack of a statistically significant

im proved survival in the patients w ho received the

H em opum p w as believed by the m anufacturer to be

due possibly to inadequate sam ple size or to the fact



8/21

F I G U R E 4. Biventricular support w ith a centrifugal pump (courtesy of Bio M edicus, Eden Prairie , M inn).

CH ES T 1102 I 5 I N O V E M B E R 1992 I S upplem ent 2 603S

the patients entered into the study were too ill and

already had irreversible shock. A new study evaluating

patients w ith less severe and hopefully potentia lly

reversible cardiogenic shock is being considered.

Com plications included blood loss at the tim e of

insertion, vascular and throm boem bolic . C linically

significant hem olysis did not occur. M oderate antico-

agulation is necessary. A 14 French percutaneous

device is under developm ent.29 Som e initial s tudiesw ith this 14 French percutaneous device dem onstrated

significant hem olysis unlike the 21 French device.29

Direct m echanical ventricular actuation is a biven-

tricular circulatory support device that can be rapidly

applied (Fig 3).7 Although it requires a surgical

procedure, it is technically sim ple. This circulatory

support device has been described as an im proved

m ethod of internal cardiac m assage. The device can

be positioned through a sm all left anterior sixth

intercostal space thoracotom y. A recent feasibility

study in patients w ith cardiac arrest dem onstrated the

average application took less than 2 m m from the tim e

of skin incision, and resulted in im m ediate hem ody-

nam ic im provem ent.74 A nstadt et al74 provided the

follow ing description of how the device w orks.The device em ploys a contoured cup w hich is pneum atically driven

to actuate the ventricular myocardium . The drive system regulates

the cups actuation (cycle rate, systolic duration, actuating forces,

and rate of force delivery) and supplies a continuous vacuum to

maintain the cups attachm ent. This vacuum creates a constant seal

between t he v en tr ic ul ar myocardium an d the actu ating d iaphragm

of the cup. D uring actuation, the ventricular m yocardium is pushed

into systole and pulled into diastole configurations creating an

action w ith remarkable effectiveness. .

A lthough D M V A w as initia lly described in the m id-

1960s, only a few studies in hum ans have been

perform ed using this device. O ne report w as a clinical

feasibility tria l dem onstrating that in patients w ith

prolonged cardiac arrest, unresponsive to traditional

m edical interventions, D M VA could be applied rap-idly.74 In fact, in 22 patients in cardiac arrest for m ore

than 40 m m , the application of the device took less

than 2 m m from the tim e of skin incision. Four patients

w ere successfully defibrilla ted; how ever, a ll subse-

quently died. Application of the device resulted in

im m ediate hem odynam ic im provem ent. D uring this

s tudy, there w as no com plication related to the device

itself how ever, a cardiac laceration occurred during

the pericardiotom y in one patient. Another evaluation

in two patients w ith cardiogenic shock dem onstrated

the device could be applied in 3 to 5 m m and could

support the circulation in both these patients .75 O ne

subsequently underwent successful cardiac transplan-tation, and the other had support discontinued because

of irreversible neurologic injury w hich occurred prior

to device insertion.

The device is capable of producing cardiac outputs

of 80 to 110 percent of control. At present,it is

believed it should be used for relatively short-term

support w ith eventual replacem ent with a m ore stan-



9/21

604S Managemen t o f C a rd ia c A rre st an d C ard iog en ic S hock Irv in F Goldenberg)

dard VA D .33 A s m ore data are obtained with this

device, its proper role w ill becom e m ore evident. This

device does have the advantage of rapid application

and does not require anticoagulation therapy.

External Centrifugal and Roller Pumps

A fter the IA BP, the centrifugal and roller pum ps

are the next m ost used m echanical assis t device. 7

This is prim arily due to their com m ercial availability,low cost, and sim plicity These devices are not inves-

tigational and can be obtained by all centers requesting

them . The devices can provide univentricular or

biventricular support (Fig4).18.59 Cannulas from the

devices (1) w ithdraw blood from the right atrium and

return it to the pulm onary artery for right ventricular

assistance, and (2) w ithdraw blood from the left atrium

or left ventricular apex and returnit to the ascending

aorta for left ventricular assistance.8 These devices

can pum p 5 to 6 11m m and can com pletely support

the circulation functioning in paralle l w ith the support

ventric le .19 Both roller and/or centrifugal pum ps are

readily available at institutions doing coronary artery

bypass surgery, as they are an integral part of the

cardiopulm onary bypass circuit used during cardiac

surgery.29 O ne could consider this one of the m ost

com m on form s of short-term m echanical circulatory

support. There are three m anufacturers w ho produce

the centrifugal pum ps (Bio M edicus, B io M edicus m c,

Eden Prairie , M inn; Sans, Sarns/3M , A nn Arbor,

M ich; and A ires M edical, W oodbury, M ass).9 The

centrifugal devices propel blood through the pum p

head w ith centrifugal force.u These pum ps are usually

nontraum atic and have good blood-handling proper-

ties.29 The Bio M edicus device generates flow by

utiliz ing a restrained vortex created by rapidly rotating

sm ooth plastic cones.29 A rapidly rotating im pella

generates flow w ith the Sarns device.29 The Sans

pum p has also been referred to as the Centrim ed

Table 6-Results of P atients Supported Postcardiotom y*

Patients

Supported W eaned Survived

Centr i fugal 72 2 356 (49)t 194 (27)

Thoratec 95 35 (37) 20 (21)

N ovacor LV A S 10 1 (10) 1 (10)

T CJ H eartm ate NA N A NA

Sym bion AV AD NA N A NA

A biom ed BVS System 5000 145 79 (54) 34 (23)Total 97 2 471 (48) 249 (25)

1. A SA IO -L SH T V olun tary R egis try3/1192, p erso na l co mm un ica -

tion ; 2 . Thoratec Clinical U pdate 1131192;3. N ovacor LV A S C linical

Update 5/3/92; 4. A biom ed, personal com m u nication , N ovem ber

1991. Modified an d p rin ted w ith perm ission from E m ery an d

Joyce.

tN um bers in parentheses indicate percent of total supported.

pum p.29 The centrifugal and roller pum ps produce

nonpulsatile flow . A lthough these devices are often

used in conjunction w ith an IA BP to produce pulsatile

flow , there are no definitive data available dem onstrat-

ing the necessity of using pulsatile flow w hen treating

patients w ith cardm ogenic 8 7929 Roller pum ps

are often the blood pum ps used w ith percutaneous

left a tria l-fem oral artery bypass,6229 w hile centrifugal

pum ps are the predom inant blood pum ps being used

w ith ECM O.M These devices are usually used for

short-term duration (less than 1 w eek), a lthough a

centrifugal device has been used for 31 days in a

patient w ho w as bridged to transplantation. Recom -

m endations on anticoagulation in patients w ith cen-

trifugal devices vary am ong the different investiga-

tors .8#{176}788283 W hile som e have recom m ended

m oderate continuous heparm n infusion throughout de-

vice im plantation, others have used little or no hepa-

rinization.89788229 A t our center, patients with cen-

trifugal pum ps are not required to receive heparin if

V AD flow is greater than 2 L. W hen VA D flow is less

than 1.5 to 2 L/m in, the patient receives continuous

Table 7-Result of VAD Support inPatients B ridg ed to T ran spla ntatio n5

Patients

Supported

Transplanted,

No . (% )

Supported Survived,

N o. (% )

T ransp lan ted S urvived,

No. (% )

Dayst

Supported

Centrifugal 99 59 (60) 35 (35) 35 (59) (1-31) 6

Thoratec 165 103 (63) 86 (52) 86 (83) (1-226) 18

N ovacor LV AS 113 67 (59) 62 (54) 62 (92) (1-370) 43

T C I-H eartm ate 56 31 (55) 27 (48) 27 (87) (1-324) 10 2

S ym bion A V A D 131t 27(N A ) 22(N A ) 22 (81) (1-164) 48A B IO M ED B V S S ystem 5000 58 42 (84) 23 (40) 23 (54) (1-30) 5

Total 491 302 (61) 233 (47) 233 (77)

1. A b iom ed A SA IO -IS H T Voluntary Registry 3/1192, personal com m unication; 2. Thoratec C linical Update 1131192; 3. Novacor LV AS

Update 5/3/92; 4.TC I personal com munication 1/1192;5. Sym b ion C linical Update 5/1191; 6. Abiom ed, personal com munication, N ovem ber

1991. M odified and printed with perm ission from references 19 and 86.

tRange and m ean days.

tln clu des all patien ts w h o received the S ym bion A V A Ddevice for any reason (b rid ge to tran splantation, postcardiotom y sh ock ,etc). N u m b e rw ho received it only as bridge to transplant is not available . The total number of patients who received the device and the nu

p atients transp lanted an d the n um ber of patien ts w h o su bsequ en tly survived after transplanta tion is available , h ow ever.

Excludes Symbion AV AD because data available areno t s im ila i to o th er d ev ic es,



10/21

F,cuas 5. Biventricular supportwith th e Pierce-D onach y T horatecventricular assist system (reproduced w ith perm ission fromPen-

nington an d Termuhlen .

CH E ST 1102 / 5 / N O V EM B E R 1992 I S upplem ent 2 605S

heparinization. For patients on a roller pum p, contin-

uous heparm n is adm inistered throughout device im -

plantation.

The advantages of the centrifugal and roller pum ps

include the following: (1) availability; (2) low cost; (3)

ability to provide biventricular support; and (4) allow s

for cannulation of either left a trium or left ventric le.

The disadvantages of these devices include the follow -

ing: (1) poor patient m obility during device im planta-

tion; (2) lack of evidence that devices can be used for

prolonged periods of tim e; (3) need for at least lim ited

heparmnization; (4 ) tendency tow ard m ore frequent

and m ore severe hem olysis;as and (5) nonpulsatile flow .

The results from using centrifugal devices in pa-

tients w ith postcardiotom y shock and as a bridge to

transplantation are show n in Tables 6 and 7.

External Pulsatile Ventricular Assist Devices

The external pulsatile V A Ds are all investigational

devices requiring FD A approval. They include the

Pierce- D onachy Thoratec V AD (Fig 5) (Thoratec Lab-

oratories Corporation, Berldey, Calif), the Pierce-

D onachy Sans Pulsatile VA D (Sans/3M , Ann A rbor,

M ich), the Sym bion A V A D (Sym bion Inc, Salt Lake

City, Utah), and the Abiom ed BV S (Biventricular

Support System 1-5000) device (A biom ed m c, Dan-

vers, M ass).8 All these are pneum atic pulsatile devices

that can provide univentricular or biventricular sup-

port. For right ventricular support, blood is w ithdraw n

from the right atrium and pum ped to the pulm onary

artery w ith all four devices . For left ventricular support

w ith the Thoratec VA D or Sans Pulsatile VA D , blood

is w ithdraw n from the left a trium or left ventric le and

pum ped to the ascending aorta. D uring left ventricularassistance w ith the Sym bion AV A D or A biom ed device,

however, blood can only be withdraw n from the left

a trium (and not the left ventricle) and pum ped to the

ascending aorta . These devices can provide full c ir-

culatory support and flows of 6 to 7 IJm in.29 The

A biom ed is extracorporeal, while the other three

devices are paracorporeal in location. The extracor-

poreal location of the Abiom ed device signfficantly

im pairs patient m obility com pared w ith the other

devices w ithin this class. Therefore, the Abiom ed has

been used only for short to interm ediate duration,

w hile the other devices have been used for short to

lo ng d ura tio n. 8 The A biom ed device has polyurethane

valves, while the other devices all have m echanical

prosthetic valves. M oderate anticoagulation is needed

w ith Sym bion AV A D and A biom ed device. Pennington

and Sw artzra.es have stated that because of the high

shear rate of blood across the valves in the Thoratec

device, anticoagulation with heparin is not required

as long as the device has been im planted for less than

1 week and flow rates are greater than 3 IJm in. Since

1990, the FD A has prohibited investigational use of

the Sym bion A VA D .

The advantages of these devices include the follow -

ing: (1) greater patient m obility for the paracorporeal

devices; (2) substantial evidence for short- and long-

term support w ith the paracorporeal devices; (3)

heparin anticoagulation requirem ents are less for the

Thoratec device; and (4) provides pulsatile flow . D is-

advantages include the follow ing: (1) the devices are

investigational and m ore difficult to obtain; (2) the cost

is increased; (3) they are m ore difficult to insert; and

(4) they require m ore sophisticated support staff.

The clinical results w hen these devices were used

for postcardiotom y shock and as a bridge for trans-

plantation are show n in Tables 6 and 7. In addition,

the duration of support (m ean and range) w ith each of

the devices w hen used as a bridge to transplant is

provided in Table 7.

Implantable Left Ventricular Assist System s

There are two im plantable left ventricular assist

system s, both of w hich are investigational and can be

used only for left ventricular support.8-#{176} The devices

are the N ovacor (Novacor LV A S, Division of Baxter,

D eerfie ld, Ill), Left V entricular Assist System (LV AS),81

and the Therm o Cardiosystem s Inc (TCI) H eartm ate



11/21

606S Managemen t of C ard iac Arrest andCardlogenic Shock Irv in F G old en be rg )

D evice29 (W oodburn, M ass). The latter device has also

been referred to as the Therm edics V AD . Both devices

provide pulsatile flow . The TC I H eartm ate is a pneu-

m atic pulsatile device,29 w hile the N ovacor is an

electrical pulsatile device. Both devices are im -

planted in the left upper quadrant of the abdom en.

The left ventricular apex is cannulated by both devices,

and blood is w ithdraw n from the left ventric le and

pum ped into the ascending aorta. Since neither deviceallow s for left atrial cannulation, these devices require

a portion of the left ventricle be rem oved w hen they

are in use.8 Therefore , these devices are less desirable

in patients w ho are likely to have recovery of their left

ventricular dysfunction e g, postcardiotom y shock).

The N ovacor pum p has a sm ooth, blood-contacting

surface, and uses pericardial tissue valves , w hile the

TCI Heartm ate uses porcine xenograft valves and has

a unique blood contacting surface that is textured to

provide for the form ation of a biologic lm ning.8 The

TCI Heartm ate does not require any anticoagulation

except for aspirin and dipyridam ole (Persantine).29

W hile som e investigators have used continuous low -

dose heparin in patients with the N ovacor LV AS,

others have suggested that heparm n anticoagulation

m ay be needed only when V AD flow rates are low ,

when the patient is being w eaned from the device, or

after postoperative day729.87

B ecause these devices supply only left ventricular

support, patients who require biventricular m echani-

cal support will either need to (1) be evaluated for a

totally different system (eg, total artific ial heart or tw o

pneum atic or centrifugal devices), or (2) receive a

hybrid system e g, treatm ent w ith im plantable LV AD

for left ventricular support and a centrifugal or exter-

nal pneum atic device for right ventricular support).

U nfortunately, the developm ent of right ventricular

failure is som etim es not identified until after one of

these im plantable devices is already in place, thus

leading to a subsequent placem ent of an RV A D at a

later tim e.87

Pulm onary Artery Balloon C ounterpulsa tion

Pulm onary artery balloon counterpulsation has

been used in postcardiotom y patients for the treat-

m ent of severe heart failure or shock secondary to

severe right ventricular dysfunction.8 Since 1980,

there have been reports of using a standard IA BP in a

graft sew n to the pulm onary artery to perform pul-

m onary artery balloon counterpulsation. The graft

sewn to the pulm onary artery acts as a reservoir for

blood and the balloon. Several reports have show n

definitive hem odynam ic im provem ent in postcardiot-

om y patients with significant right or biventricular

dysfunction. M ost reports , how ever, have included,

at m ost, a few patients. B ecause of the technical

com plexity of the procedure and the availability of

other assist devices, there has not been significant

application of this procedure in patients w ith postcar-

diotom y right ventricular dysfunction. A pulm onary

artery balloon that can be positioned into the pulm o-

nary artery percutaneously has been developed and

evaluated in anim als.29 U ntil a percutaneous pulm o-

nary artery balloon catheter is available clinically , I

suspect this procedure w ill receive only rare applica-

tion, especially at centers that have experience inplacing other RVA D s. It should, how ever, be consid-

ered as an option, particularly at centers that do not

have access to other RV AD s.

O rthotopic B iventricular Replacem ent Prosthesis

ArtJicia l H eart)

Since 1969, 11 different m odels of the total artificia l

heart have been used for tem porary or perm anent

circulatory support in 226 patients.5 Two hundred

thirty total artificia l hearts w ere placed in 226 pa-

tients.5 The total artific ia l heart w as used as a per-

m anent circulatory support device in five patients,

while the rem aining 221 patients (225 im plants) had

the total artific ia l heart placed as a bridge to trans-

plantation.5 O nly lim ited data are available on the 18

recipients of the Poisk and C zech total artific ia l heart.

The data on the 207 rem aining im plants (182 patients)

are sum m arized.5 Of the 207 im plants, 186 were w ith

a Sym bion total artificia l hearts (previously called the

Jarvik 7-70 and Jarvik 7 total artific ial hearts). Of the

207 im plants, 135 (65 percent) subsequently under-

w ent orthotopic cardiac transplantation. A t 1 year

postcardiac transplantation, 67 patients (50 percent)

w ere alive. O f the 39 non-Sym bion total artific ial heart

im plants, there w as only one (3 percent) long-term

survivor. The one non-Sym bion total artific ial heart

long-term survivor had a sm all Vienna heart placed.

H ow ever, in the patients w ho received a Sym bion total

artific ial heart, 40 percent survived 1 year, while 56

percent of the patients in this group w ho subsequently

underw ent transplantation survived 1 year.5

A description of all 11 m odels of the total artific ia l

heart is beyond the scope of this review. H ow ever,

because the m ajority of the im plantations w ere from

the Sym bion total artific ia l heart, a description of that

device w ill follow.

The Sym bion total artific ial heart is a pneum atic

device that consists of tw o separate ventric les (Fig 6).

A ll four valves are M edtronic-H all m echanical pros-

thetic valves. The artificia l right and left ventric les are

secured to the native right and left a trium , pulm onary

artery, and aorta . There are two versions of the

Sym bion total artificia l heart-the Sym bion 7 and

Sym bion 7-70, with the stroke volum e being 100 m l

and 70 m l, respectively. The tim e spent supporting

the circulation with the Sym bion total artific ial heart

as a bridge to transplant ranges from 1 to 603 days



12/21

C HE ST / 102 I 5 I N O V E M B E R 1992 I S upplem ent 2 607S

F I G U R E 6. S ym bion t ot al a rt if ic ia l heart.

w ith a m ean tim e of 26 days and the m edian w as 8

days.5 Infection, bleeding, and renal failure were them ost com m on side effects from the total artffic ia l

heart. N eurologic events occurred in only 5 percent

of the patients who received the total artific ia l heart

as a bridge to transplantation.

A ll five patients w ho received the Sym bion total

artificia l heart as a perm anent device died.5 Range of

im plantation in these patients ranged from 10 to 620

days w ith 80 percent of the patients living m ore than

30 days.5 D eath in the five patients occurred from

sepsis in four and from surgical bleeding in one.15

Since January 1990, the FD A has prohibited the sale

of Sym bion total artificia l hearts in the U nited States.

Perm anent Devices

Five patients had the Sym bion total artificia l heart

im planted as a perm anent device before the FD A

prohibited further im plants. These patients were

described in the previous section of this report. In

addition, tw o patients had received an IA BP w ith the

intent on using it as a perm anent device.4 One of

these patients had the device rem oved after 8 w eeks

because of a fever of unknown origin. The other

patient died of renal failure 38 days after device

im plantation. A t present, investigational w ork in clin-ical studies are beginning in regard to im plantation of

a perm anent prototype of the Novacor LVA S. W hile

no other device is presently undergoing clinical eval-

uation, s ignificant w ork is being done in developing

other im plantable V AD s and total artific ia l heats for

perm anent use. Since the num ber of patients aw aiting

cardiac transplantation, presently and in the fore-

seeable future , far outw eigh the num ber of donor

hearts available , there are a substantial num ber of

patients w ho could obviously benefit from the devel-

opm ent of perm anent ventricular assist or replace-

m ent devices.

C om plications in Patients W ith M echanical Assist

Devices

The m ost com m on com plications in patients with

m echanical assist devices include bleeding, renal

failure , infection, and throm boem bolic events.829 In

devices that are im planted percutaneously, vascular

com prom ise is also another significant problem .18 In

patients on a m echanical assist device w ho are being

bridged to cardiac transplantation, their survival is

significantly lower if they have significant bleeding,

renal failure , or infection.8 In patients with postcar-

diotom y shock, the developm ent of renal failure orperioperative m yocardial infarction is associated with

a poorer prognosis.8 Rarely, hypoxia secondary to

Table 8-C oronary Angioplasty fo r C ardiogenic Shock Com plicating Acute M yocardial Infarction5

Reperfusion

M ortality Rate

{149}

Study N o. Rate Total + Reperfusion - Reperfusion

ONeill et al 27 24/27 [88] 8/27 [30] 6124 [25] 2/3 [67]

Shani et al 9 6/9 [67] 3/9 [33] N/A N /A N /A N/A

Heuser et al#{176} 10 6/10 [60] 4/10 [30] 1/6 [17] 3/4 [75]

Brow n et aln 28 17/28 [61] 16/28 [57] 7/17 [42] 9/11 [82]

Laram ee et al 39 33/39 [86] 16/39 [41] N/A N /A N /A N/A

Lee et al 24 13/24 [54] 12/24 [50] 3/13 [23] 9/11 [82]

Lee et aP 69 49/69 [71] 31169 [45] 15/49 [31] 16/20 [80]GaciochandTopol 25 18/25 [72] 11/25 [44] 4/18 [22] 7/7 [100]

Disler et al#{176} 7 5/7 [71] 417 [57] 2/5 [40] 2/2 [100]

Vernaetalbo6 7 7/7 [100] 1/7 [14] 1/7 [14] 0/0 [0]

M eyer et al#{176} 25 22./25 [88] 12/25 [47] 9/22 [41] 3/3 [100]

Hibbard et al 45 28/45 [62] 20/45 [44] 8/28 [29] 12/17 [71]

M oosvi et al 38 29/38 [76] 18/38 [47] 11/29 [38] 7/9 [78]

Eltchaninoffet al 33 25/33 [76] 12/33 [36] 6/25 [24] 6/8 [75]

Total 386 282/386 [73] 168/386 [44] 73/243 [30] 76/95 [80]

*D ata represent patient num bers. Numbers in brackets represent percents. N /A= not available; plus sign= w ith; m in us sign = without.

Printed w ith perm ission from Bates and Topol.L2



13/21

608S M anagem ent of C ardiac Arrest and Cardiogenlc S hock Irv in F O oId en be i

right-to-left shunting across a patent foram en ovale

occurs in patients w ith an LV AD .29

Skeletal M uscle-Powered Cardiac Assistance

At present, em ergent use of skeletal m uscle-pow -

ered cardiac assistance is not possible for the treatm ent

of cardiogenic shock or cardiac arrest. D ynam ic car-

diom yoplasty, however, has been used clinically for

the treatm ent of patients with severe congestive heartfailure .29 It is, however, conceivable that with signifi-

cant further advances in cardiom yoplasty, atriom yo-

plasty, dynam ic aortom yoplasty, or skeletal m uscle-

pow ered cardiac assist devices , these interventions

could potentia lly be used for the long-term treatm ent

in patients w ith cardiogenic shock w hose circulation

had been initially stabilized and supported w ith m e-

chanical circulatory support devices.29 Further inves-

tigation in this area, how ever, is needed.29

PERCU TA NEOU S INTERVEN TIO NA L PRO CEDU RES

Percutaneous M echanical Revascularization

Coronary angioplasty, directional or rotational athe-

rectom y, coronary laser angioplasty, and coronary

stenting are percutaneous interventional procedures

that im prove coronary artery patency and can poten-

tia lly reverse m yocardial ischem ia and im prove he-

m odynam ics in patients with cardiogenic shock.12.912 9

A n evaluation of 14 studies that assessed the efficacy

of em ergency coronary angioplasty for cadiogenic

shock due to a m yocardial infarction w as recently

reviewed by Bates and Topol (Table 8).12 A sum mary

of the 14 studies dem onstrated that patency rates for

em ergency angioplasty in acute m yocardial infarction

and cadiogenic shock are low er than in other patients

w ith acute infarction.2 Successful reperfusion in those

studies ranged from 62 percent to 100 percent,

averaging 73 percent. The m ortality rate in the 14

studies ranged from 14 percent to 57 percent, aver-

aging 44 percent. This w as a significant reduction in

m ortality when com pared with m ortality rates for

m edical therapy alone in his torical controls. In the 73

percent of patients w ho had successful reperfusion

from coronary angioplasty, the m ortality rate w as 30

percent, while in the patients w ho did not have

successful reperfusion, the m ortality rate w as 80

percent.2 The latter m ortality rate was not signifi-

cantly different from w hat one would expect from

m edical intervention alone. The authors of this m eta-

analysis convincingly showed coronary angioplasty

im proves survival in patients w ith cadiogenic shock

and an acute m yocardial infarction. They also pre-

sented data to suggest throm bolytic agents have a very

low reperfusion rate in these patients and provide no

evidence that these agents are effective in reducing

m ortality in acute m yocardial infarction and cardio-

genic shock.12,110.hhl In fact, the data w ould suggest

that throm bolytic agents do not favorably affect m or-

ta lity in patients w ith cardiogenic shock.#{176}

In addition to coronary angioplasty, there are other

percutaneous interventional procedures eg , coronary

atherectom y,h12 laser angioplasty, and coronary stent-

ing) that should be helpful in producing coronary

reperfusion in the setting of an acute m yocardial

infarction w ith cardiogenic shock. A lthough these

latter procedures are likely to be helpful in the settingof acute m yocardial infarction and cardiogenic shock,

either when used alone or in conjunction with coro-

nary angioplasty, there are few data presently available

with these devices in this clinical situation.

In addition to the above procedures, w hich are

generally used with the hope of perm anently im prov-

ing coronary blood flow and cardiac function, there

are additional percutaneous interventional procedures

that can be used to tem porarily im prove m yocardial

oxygenation andfunction.683 A ugm entation of dista l

coronary artery perfusion m ay be accom plished (1)

passively through autoperfusion catheters eg , bailout

or perfusion balloon catheters), and (2) actively by

pum ping oxygenated blood or fluorocarbons through

the central lum en of an angioplasty catheter.29 In

addition, im proved m yocardial oxygenation and func-

tion can be accom plished by synchronized coronary

sinus retroperfusion w ith arterial blood6 1 Percuta-

neous synchronized coronary sinus retroperfusion

delivers pulsatile blood retrogradely through the car-

diac veins to the coronary bed dista l to a coronary

stenosis .293 A ll three of these latter interventions

im prove m yocardial oxygenation and m yocardial func-

tion and can im prove hem odynainics in som e patients

w ith acute m yocardial infarction or acute coronary

closure and cardiogenic shock while m ore definitive

interventions are being im plem ented. R ecently, these

interventions w ere extensively review ed by Lincoff et

al29 and w ill be only briefly discussed herein. By

im proving m yocardial oxygenation and function and

im proving hem odynam ics, these interventions stabi-

lize the patients condition and decrease m yocardial

necrosis w hile the patient undergoes percutaneous or

surgical reperfusion or revascularization. For synchro-

nized coronary sinus retroperfusion, an infla table

balloon-tipped coronary sinus catheter is placed per-

cutaneously through a 9 French sheath that has usually

been placed in the right internal jugular vein.3 It isthen advanced into the coronary sinus and preferably

into the great cardiac vein.3 A rteria l blood usually

obtained from a fem oral artery is infused into the

coronary sinus during ventricular diastole. A n advan-

tage to synchronized coronary sinus retroperfusion is

the catheter does not have to be placed across an

occluded or stenotic coronary artery, w hich at tim es

m ay not be possible . D isadvantages to coronary sinus

retroperfusion are (1)it m ay, on occasion, not be



14/21

CH ES T / 102 / 5 / NO VE M B ER 1992 I Supplement2 609S

possible to cannulate the coronary sinus, and (2) in

som e patients , incom plete m yocardial protection m ay

be provided with this device. In addition, coronary

sinus retroperfusion has been perform ed predom i-

nantly in patients who had m yocardial ischem ia in-

duced from left anterior descending artery stenosis or

obstruction. It is unclear how well coronary sinus

retroperfusion w ould protect against ischem ia from

the circum flex or right coronary artery because theright coronary artery, and to a lesser extent the

circum flex, often drain directly into the right atrium ,

right ventric le, or an area of the coronary sinus that

w ould not be perfused by a coronary sinus catheter

advanced into the great cardiac vein.29

K ar and cow orkers3 reported the reversal of severe

chest pain, hypotension, cardiogenic shock, com plete

heart block, and global hypokinesis w ithin m inutes of

initia ting percutaneous synchronous coronary sinus

retroperfusion in a patient with acute closure of the

left anterior descending artery. This allow ed stabili-

zation of the patients condition while further attem pts

at angioplasty w ere m ade to open the coronary artery.

W hen this failed, the patient w ent to coronary bypass

surgery hem odynam ically stable .

Transcatheter C losure of Ventricular Septa l D efects

Lock et al described their initia l results with

attem pted transcatheter closure of ventricular septal

defects. Three of the six patients had a recent m yocar-

dial infarction and w ere in cardiogenic shock. The

conditions of two of the patients initia lly im proved,

but subsequently deteriorated. This initia l study

w ould not suggest this procedure could be used as

definitive treatm ent for a ventricular septal defectassociated with cardiogenic shock secondary to a

m yocardial infarction. H ow ever,it m ay be helpful in

initial stabilization of som e patients conditions prior

to subsequent em ergent surgery. H opefully, w ith

further im provem ent and advances in the procedure,

long-term results m ay im prove.

Percutaneous Aortic Valvuloplasty

Patients w ith critical aortic stenosis w ill rarely

present in cardiogenic shock. W hile som e physicians

have favored em ergency valve replacem ent w hen this

occurs, others have believed that operative risk is

prohibitive. A t other tim es, patients m ay refuse cardiac

surgery. There have been a lim ited num ber of reports

dem onstrating that em ergency balloon aortic valvu-

loplasty can significantly im prove hem odynam ics.56

A fter the patients hem odynam ics have stabilized,

m ore elective aortic valve replacem ent can be sched-

In one study w here surgery w as delayed and

catheterization w as repeated approxim ately 6 m onths

after initial valvuloplasty, patients dem onstrated a

significant sustained im provem ent in their hem ody-

nam ics over initia l presentation, including a significant

increase in their ejection fraction.5 Thus, in this

group of patients, not only was aortic valvuloplasty a

life-saving treatm ent for their aortic stenosis and

cardiogenic shock, it also significantly im proved their

ejection fraction prior to subsequent surgery for aortic

valve replacem ent, leading to a decrease in their risk

o f s ur ge ry .

Other Percutaneous P rocedures U sed to Treat

Cardiogenic Shock

Additional percutaneous interventional procedures

helpful in the treatm ent of cardiogenic shock include

(1) pacem aker placem ent to optim ally control heart

rate and atrioventricular (A V ) delay, (2) catheter or

chem ical ablation of arrhythm ias, and (3) pericardio-

centesis.

CA RD IA C SU RG ERY

Coronary Artery Bypass G raft Surgery

Coronary artery bypass graft surgery has been used

as an effective treatm ent for cardiogenic shock sec-

ondary to an acute m yocardial

B ates and Topol2 recently perform ed a m eta-analysis

on the m ortality of patients w ho underwent coronary

artery bypass surgery for cardiogenic shock com pli-

cating an acute m yocadial infarction (Table 9). Sixteen

studies w ere review ed during the period from 1973 to

1989. 12,43.t17429 There were 216 patients w ho under-

w ent coronary artery bypass graft surgery with a

m ortality rate of 40 percent (87 of the 216 patients).

In the eight studies published since 1980, there w ere

15 0 patients w ith only a 31 percent m ortality (47 of

Table 9-Coronary Artery Bypass Graft Surgery forCardiogenic Shock Complicating Acute M yocardial

lnfarction*

Study Year No. Mortality

M undth et al 1973 33 20 [61]

M iller et a 1974 12 7 [58]W illerson et al 1975 3 2 [67]

Johnson et al#{176} 1977 5 3 [60]

Ehrich et aP 1977 3 2 [67]

Bardet et al 1977 4 2 [50]

O Rourke et al 1979 6 4 [67]

Subramanian et al 1980 20 9 [45]M erav et al (cited in 1980 7 2 [29]

DeW ood et al 1980 19 8 [42]

Kirklin et ale' 1985 4 0 [0]

Phillips et al 1986 34 8 [24]

Laks et al' 1986 50 15 [30]

G uyton et a ' 1987 9 2 [22]

Bolooki 1989 7 3 [43]

Total 21 6 87 [40)

8D ata represent patient num bers. Numbers in brackets represent

percents. Printed w ith perm ission from Bates and Topol.



15/21

610S M anagem ent of C ardiac A rrest and C ardiogenic S hock I rv in F G old en be rg )

1 50 p atie nts ). I2,43. 4-129 W hen coronary artery bypass

surgery is perform ed in the setting of an acute

m yocardial infarction and cardiogenic shock,it should

be perform ed as early as possible. D eW ood and

cow orkers43 reported that patients who underwent

bypass surgery less than 16 h after the onset of their

infarction had only a 25 percent m ortality, w hile

patients w ho underw ent coronary artery bypass sur-

gery m ore than 18 h after the onset of their sym ptom shad a 71 percent m ortality . Presently available data

would suggest that patients with acute m yocardial

infarction and cardiogenic shock, even without a

m echanical defect, should undergo either percutane-

ous m echanical or surgical revascularization if they

present early in their infarction or have evidence for

ongoing ischem ia. 12.43,96-1o9.117-129

O ther Cardiac Surgical Procedures

O ther cardiac surgical procedures that have been

helpful in the treatm ent of cardiogenic shock include

the following: (1) repair of ventricular septal defect29

or free w all rupture secondary to a m yocardial infarc-

tion or traum a; (2) valve repair or replacem ent in

patients w ith acute valvular obstruction or regurgi-

tation29 (from m ultiple causes , including m yocardial

infarction, endocarditis, traum a, atrial m yxom a, etc);

(3) pericardial w indow to rem ove pericardial fluid or

rem oval of an extrinsic cardiac m ass causing cardiac

tam ponade; (4) pulm onary em bolectom y in patients

with acute m assive pulm onary em bolism ; (5) aneurys-

m ectom y for aneurysm contributing to refractory

arrhythm ias or cardiogenic shock; and (6) surgical

treatm ent of refractory arrhythm ias eg , ablation or

resection). In addition, pericardiectom y has been

suggested for som e patients w ho have right ventricular

infarction and cardiogenic shock.130.132

C ardia c T ransp lanta tion

Patients w ho have cardiogenic shock and irreversi-

ble cardiac dysfunction need cardiac transplantation

or im plantation of a perm anent m echanical assis t

device for survival. Since protocols for perm anent

VA D s are just beginning, m ost of these patients, if

they are to survive, w ill undergo cardiac transplanta-

tion. Since 1967, there have been approxim ately

13,000 cardiac transplantations perform ed at 230

transplant centers.lu Presently 97.5 percent of thepatients have undergone orthotopic cardiac transplan-

tation, while 2.5 percent have undergone heterotopic

cardiac transplantation.1x1 A ccording to the Registry

for the ISH T, the 1- and 5-year actuaria l survival is 83

percent and 75 percent, respectively. However,

som e experienced program s do have 1-year survivals

of 90 to 95 percent. Because of the severe donor

shortage, approxim ately 30 percent of patients aw ait-

ing cardiac transplantation die prior to receiving a

transplant. In patients w hose conditions deteriorate

prior to transplantation, a m echanical circulatory assist

device can be used to support them until transplan-

tation.

CLIN ICA L SITU ATION S

Acute M yocardia l Infarction and C ardiogenic Shock

Optim al treatm ent for patients w ith acute m yocar-

dial infarction and cardiogenic shock consists of thefollow ing: (1) early restoration of coronary blood flow

to the infarct-related artery; (2) correction of any

m echanical com plications associated w ith an acute

infarction eg , ventricular septal defect, papillary

m uscle rupture w ith m itral regurgita tion, cardiac

rupture, infarct expansion w ith aneurysm al form ation)

that m ay be contributing to the cardiogenic shock;

and (3) providing adequate circulatory supportY 3 In

the m ajority of patients presenting early after an acute

m yocardial infarction and in cadiogenic shock, rapid

and early restoration of coronary blood flow with

throm bolytic therapy, percutaneous m echanical revas-

culanzation (percutaneous translum inal coronary an-

gioplasty, directional and rotational atherectom y, laser

angioplasty, etc), or surgical revascularization is likely

to have the greatest im pact on im proving ventricular

function and survival.3 The success of these inter-

ventions depends heavily on the tim e betw een the

onset of coronary artery closure and the restoration of

effective coronary blood flow. A lthough present data

w ith intravenous throm bolytic therapy for the treat-

m ent of patients with acute m yocardial infarction and

cardiogenic shock do not dem onstrate any significant

im provem ent insurvival,1b0lhI these agents should

probably be adm inistered if there is to be any delay in

perform ing em ergent cardiac catheterization and re-

vascularization. Patients should undergo em ergency

coronary angiography, and if anatom y is appropriate ,

acute percutaneous m echanical revasculariza-

tion.296-109 Patients w ho present early in their infarc-

tion and/or w ho have evidence for ongoing ischem ia

should have surgical revascularization perform ed if (1

percutaneous m echanical revascularization is unsuc-

cessful or unfeasible , and (2) if they have appropriate

coronary anatom y. I2,43.1I7 9 N onrandom ized trials have

show n significant im provem ent in survival in patients

w ith acute m yocardial infarction and cardiogenic

shock when treated w ith coronary angioplasty or

coronary artery bypass surgery com pared w ith histor-

ical control subjects treated m edically .34396-109729 T

im prove m yocardial oxygenation during percutaneous

m echanical revascularization or surgical revasculari-

zation, one should consider interventions that are

tem porarily helpful at increasing dista lcoronary artery

perfusion (eg, perfusion catheter, percutaneous syn-

chronized coronary sinus retroperfusion).293 These

latter interventions are not appropriate for all patients,



16/21

C HE S T 1102 I 5 I N O V E M B E R 1992 / S upplem ent 2 611S

and their use w ill need to be individualized. Som e

patients w ho present with m ultivessel disease and

have adequate perfusion w ith coronary angioplasty

still do poorly and should be considered for coronary

artery bypass surgery.

A ll patients should also be evaluated by Doppler

echocardiography and heart catheterization for m e-

chanical com plications of acute m yocardial infarction

that m ay be contributing to the cardiogenic shock. Ifm echanical com plications are present, these patients

should receive appropriate surgical therapy. A l-

though patients with acute m yocardial infarction who

present w ith a ventricular septal defect and cardio-

genic shock w ill require surgical intervention, a rare

patient w ith this problem has had his or her condition

transiently stabilized w ith percutaneous transcatheter

closure of their ventricular septal defects .4 Initia l

w ork, how ever, does not suggest this procedure can

be used as definitive treatm ent for ventricular septal

defects associated w ith an acute m yocardial infarc-

tion.4 This procedure m ay be helpful in initial

stabilization of som e patients conditions prior to

subsequent urgent cardiac surgery. An exact role for

this treatm ent in patients with acute m yocardial

infarction w ill need to aw ait further trials.

Patients w ith right ventricular infarction and car-

diogenic shock m ay have special problem s that require

additional interventions. Intrapericardial pressure has

been show n to be elevated in anim als w ith right

ventricular infarction.3 Pericardiectom y in these an-

im als has been show n to im prove hem odynam ics. This

has led som e authors to recom m end pericardiectom y

as treatm ent in som e patients w ith right ventricular

infarction. {176}In addition, severe tricuspid regurgita-

tion secondary to acute right ventricular papillary

m uscle infarction treated w ith tricuspid valve replace-

m ent has been helpful in treating cardiogenic shock

in a rare patient with right ventricular infarction.37

A lthough A V sequentia l pacing m ay be im portant for

any patient w ith heart block in cardiogenic shock,

patients w ith right ventricular infarction appear to be

particularly dependent on their atria l contribution to

cardiac output, and therefore , these patients w ho

have evidence for AV dissociation, which could be

contributing to cardiogenic shock, w ill need to be

treated with urgent AV sequentia l pacing.

W hile attem pts are being m ade to restore coronary

perfusion and to perform a diagnostic evaluation,

interventions to provide circulatory support should

also proceed. In patients with hem odynam ic instabil-

ity not responsive to pharm acologic treatm ent, m e-

chanical circulatory assist devices m ay be needed to

provide tem porary support for (1) patients w ith re-

versible cardiac ischem ia and/or m echanical com pli-

cations of an acute m yocardial infarction until correc-

tive cardiac procedures can be perform ed ie , coronary

artery bypass surgery, ventricular septal defect repair),

or (2) patients with irreversible cardiac dam age as a

bridge to cardiac transplantation. In addition, som e

patients who are not candidates for corrective cardiac

surgery or cardiac transplantation w ill require tem -

porary circulatory support. Because stunned m yocar-

dium m ay take days to weeks to recover, prolonged

use of m echanical circulatory assist devices m ay be

needed in som e patients before they can be w eaned.In patients with cardiogenic shock not responsive

to pharm acologic therapy, placem ent of an IA BP w ill

tem porarily resolve the shock in 75 percent of the

patients.39 If shock persists despite an IA BP or if m ore

com plete circulatory support is obviously needed,

other resuscitative devices (fem oral-fem oral percuta-

neous cardiopulm onary bypass, Hem opum p,43 per-

cutaneous left a trial fem oral arterybypass62) should

be placed. Percutaneous cardiopulm onary bypass sup-

port is available at m any centers and can usually be

com pleted w ithin 15 m m . The H em opum p has been

inserted in 29 patients with m yocardial infarction w ith

15 patients (52 percent) being w eaned and 10 patients

(35 percent) being discharged (Johnson and Johnson

sum m ary report of m ulticenter clinical tria l of He-

m opum p in patients w ith cardiogenic shock: unpub-

lished data). In the ten patients w ith m yocardial

infarction in whom the H em opum p insertion w as

attem pted but unsuccessful, only tw o (20 percent)

patients survived (Johnson and Johnson sum m ary

report of m ulticenter clinical tria l of H em opum p in

patients w ith cardiogenic shock: unpublished data).

Pneum atic and centrifugal V A Ds and the total artific ia l

hearts have also been used to provide circulatory

support when (1) som e of the other devices m entioned

above w ere not available, (2) greater circulatory sup-

port was needed, (3) prolonged circulatory support

w as needed, (4) cardiac corrective surgery w as being

perform ed, or (5) the patient w as being bridged to

transplant. W illerson and Fraziers

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Pathogenesis and Management of Cardiogenic Shock and Postoperative Shock. Introduction. Chest 1992

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