Ffr, raf, shunt calculation, pvr

FFR

Introduction• Fractional flow reserve (FFR) measurement involves

determining the ratio between the maximum achievable blood flow in a diseased coronary artery and the theoretical maximum flow in a normal coronary artery. An FFR of 1.0 is widely accepted as normal. An FFR lower than 0.75-0.80 is generally considered to be associated with myocardial ischemia (MI).

• FFR is easily measured during routine coronary angiography by using a pressure wire to calculate the ratio between coronary pressure distal to a coronary artery stenosis and aortic pressure under conditions of maximum myocardial hyperemia.This ratio represents the potential decrease in coronary flow distal to the coronary stenosis

The ability of the cardiologist to discriminate between lesions that can cause MI and lesions that are physiologically insignificant on the basis of coronary angiography alone is limited.

The use of FFR measurement provides the cardiologist with a straightforward, readily available, quantitative technique for evaluating the physiologic significance of a coronary stenosis.

IndicationIndications for FFR measurement are as follows:• To determine the physiologic and hemodynamic significance of

an angiographically intermediate coronary stenosis• To identify appropriate culprit lesion(s) in multivessel coronary

artery disease (CAD)• To measure the functional importance of stenosis in the

presence of distal collateral flow• To identify the precise location of a coronary lesion when the

angiographic image is unclear

N.B. this procedure is not intended for use in the setting of a total vessel occlusion.

Equipment

Manufacturer: Volcano Corporation and St Jude Medical, Inc.

FFR equipment manufactured by Volcano :1. ComboMap Pressure and Flow System - This is a

combined system that displays both pressure and flow

2. ComboWire XT Guide Wire - This wire allows simultaneous measurement of intravascular pressure and Doppler flow and, thus, is capable of measuring stenotic and microvascular resistance

Volcano equipment…

3. PrimeWire Guide Wire - This wire allows measurement of intravascular pressure

4. FloWire Doppler Guide Wire - This wire allows measurement of coronary arterial blood flow velocity and coronary flow reserve

St. Jude equipment…

RadiAnalyzer Xpress - This combined system takes pressure, flow, and temperature measurements using 1 PressureWire and 1 instrument

Technique• Typically, conscious sedation is administered as part of the

cardiac catheterization• Wet the working length of the guide wire with normal

saline, and insert the wire through the appropriate introducer components and guiding catheter into the desired blood vessel

• Slowly advance the guide wire tip under fluoroscopic guidance, using contrast injections to verify its location

• operator crosses the coronary stenosis with an FFR-specific guide wire designed to record the coronary arterial pressure distal to the stenosis.

Technique cont’d…• The pressure transducer is located approximately 20 mm

proximal to the distal tip of the wire, and it can be seen fluoroscopically.

• Once the transducer is distal to the stenosis, a hyperemic stimulus is administered by injection through the guide catheter, and the FFR is monitored for a significant change.

• To achieve maximum hyperemia, adenosine is typically used: a 15-30 µg bolus in the right coronary artery, a 20-40 µg bolus in the left coronary artery, or intravenous (IV) infusion for 3-4 minutes at 140 µg/kg/min.

• The mean arterial pressures from the pressure wire transducer and from the guide catheter are then used to calculate FFR.

Pressure Transducer

Cont’d…

• An FFR value lower than 0.75 indicates a hemodynamically significant stenosis. An FFR value higher than 0.8 indicates a stenosis that is not hemodynamically significant. Values between 0.75 and 0.80 are indeterminate

Risk or complication

1. Risks specific to the FFR procedure include the need for additional contrast use and radiation exposure, as well as a slightly increased risk of coronary arterial dissection with FFR wire passage

2. Risk of left heart catheterization

Complications associated with cardiac catheterization include the following:

• Coronary vessel dissection, occlusion, or perforation• Embolism (coronary, cerebral, or other arterial)• Coronary artery spasm• Local or systemic infection• Acute renal failure• Myocardial infarction• Stroke• Serious arrhythmias• Death

RAF

Introduction

RF energy, a low-voltage, high-frequency form of electrical energy similar to electrocautery used in surgery

RF energy produces small, homogeneous, necrotic lesions by heating tissue. With typical power settings and good catheter contact pressure with cardiac tissue, lesions are minimally about 5-7 mm in diameter and 3-5 mm in depth.

Indications

Common indications:There are three class I indications for catheter

ablation1. SVT due to AVNRT, WPW syndrome, unifocal

atrial tachycardia, or atrial flutter (especially common right atrial forms).

2. AF with lifestyle-impairing symptoms and inefficacy or intolerance of at least one antiarrhythmic agent.

Ind. Cont’d…

3. Symptomatic VT. Catheter ablation is first-line therapy in idiopathic VT if that is the patient’s preference. In structural heart disease, catheter ablation is generally performed for drug inefficacy or intolerance or as adjunctive therapy to patient with ICD.

Cont’d…

Uncommon indication:1. Symptomatic drug-refractory (inefficacy or

intolerance) idiopathic sinus tachycardia2. Lifestyle-impairing ectopic beats3. Symptomatic junctional ectopic tachycardia

Contraindications

1. Left atrial ablation and ablation for persistent atrial flutter should not be performed in the presence of known atrial thrombus.

2. Mobile left ventricular thrombus would be a contraindication to left ventricular ablation.

3. Mechanical prosthetic heart valves are generally not crossed with ablation catheters.

4. Pregnant.

Preprocedural planning

Inv.: ECG Echocardiography ETT/ LHC- in specific casesCardiac medications with electrophysiologic effects

(eg, beta blockers, calcium channel blockers, digoxin, and class I and III antiarrhythmic drugs) are often tapered or discontinued before the procedure.

Warfarin may or may not be held prior to the procedure

Instruments

Ablation Catheter tip

Electrode Catherter

Ablation catheter

Technique• Typically, two to five electrode catheters are

percutaneously inserted via the femoral or internal jugular veins and are positioned within the left heart, the right heart, or both

• Usually positions are high right atrium, Coronary sinus, RV apex, His bundle.

• For left-heart catheterization, one of the following two approaches may be taken:

Transseptal catheterization via the interatrial septum Retrograde catheterization across the aortic valve

• Anticoagulation with intravenous (IV) heparin is used to reduce the risk of periprocedural thromboembolism.

• Specific location to ablate for specific arrythmia

AF: Target is 4 pulmonary veins

Electr-Anatomic mapof post left atrium

Atrial Flutter: Target is Cavotricuspid isthmus

AVNRT: Slow pathway ablation site

VT: Right ventricular outflow tract

WPW syndrome: Target is accessory pathway

Complications

Major complications occur in approximately 3% thromboembolism in fewer than 1% and death in 0.1-0.2% of all procedures

Cardiac complications:• High-grade AV block• Cardiac tamponade (highest in AF ablation, up to 6%)• Coronary artery spasm/thrombosis• Pericarditis• Valve trauma

N.B.: Radiation risk from catheter ablation is low, but it may exceed the risk from common radiologic procedures.

Vascular complications, which occur in approximately 2-4% of procedures, include the following:

• Retroperitoneal bleeding• Hematoma• Vascular injury• Transient ischemic attack/stroke• Hypotension• Thromboembolism or air embolism

Pulmonary complications include the following:• Pulmonary hypertension, with or without

hemoptysis (secondary to pulmonary vein stenosis)

• Pneumothorax

Miscellaneous complications include the following:• Left atrial–esophageal fistula• Acute pyloric spasm/gastric hypomotility• Phrenic nerve paralysis• Radiation- or electricity-induced skin damage• Infection at access site• Inappropriate sinus tachycardia• Proarrhythmia

Assessment of shunt by cardiac catheterization

Format of shunt calculation

Cont’d…

Shunt by cardiac catheterization

Disease Present diagnostic catheterization indicationASD , VSD , PDA For pul. resistance and reversibility Of pulmonary

HTNComplex pulmonary atresia

Detailed characterization of lung segmental pulmonary vascular supply when noninvasive imaging methods incompletely define pulmonary artery anatomy

PA with intact IVS Determination of coronary circulationSupravalvar AS useful to define relationship to CA originsTOF Anatomy when CAs, VSDs, Ao-PA collaterals cannot

be sufficiently imaged otherwise

Single ventricle Hemodynamics/PVR

1. L – R shunt

2. R – L shunt



1. Pulmonary artery [PA] blood oxygen saturation is >80%, the possibility of a left-to-right intracardiac shunt should be considered .

When to suspect cardiac L – R shunt ?

Plan of management by catheterisation:

1. Diagnosis2. Quantification of shunt3. Hemodynamic load

1. Oximetry run2. Flow ratio3. Indicator dye dilution technique4. Angiography 5. Pressure mearement


Left-to-right Intracardiac Shunts

• In the oximetry run the oxygen content or % saturation is measured in PA,RV,RA,VC.

• A left-to-right shunt may be detected and localized if a significant step-up in blood oxygen saturation or content is found in one of the right heart chambers

• A significant step-up is defined as an increase in blood oxygen content or saturation that exceeds the normal variability that might be observed if multiple samples were drawn from that cardiac chamber.

1. Left-to-right Intracardiac Shunts - Oximetry run


Various methods used for oximetry run are1. Oxygen content 2. Oxygen saturation

Spectrophotometry Oxygen dissociation curve

Oxygen content = O2 bound to Hb + dissolved O2 Dissolved O2 = 3.26 * PaO2 / 100. Oxygen saturation = O2 bound to Hb / O2 capacity * 100 Oxygen capacity = Hb * 13.6

Shunt by cardiac catheterization1. Left-to-right Intracardiac Shunts - Oximetry run

• Oxygen content The technique of the oximetry run is based on the

pioneering studies of Dexter and his associates in 1947Oxygen content was measured by Van Slyke

technique , and other manometric studiesProposed step up at atrial , ventricular , pulmonary

artery level are 2%, 1%, 0.5%.Disadvantages of oxygen content technique

15 – 30 min for obtaining a reading Technically difficult to performDependency on Hb content


• Oxygen content Manometric to spectrophotometric methodSpectrophotometric is technically easy and results are with 1 minOxygen content is calculated by saturation by

= O2 sat. * Hb % * 1.36When oxygen content is derived in this manner, rather than by

direct oximetric technique, the value is no more accurate (presence of carboxyhemoglobin or hemoglobin variants with O2 capacity other than 1.36).

1. Left-to-right Intracardiac Shunts - Oximetry runShunt by cardiac catheterization

• Oxygen saturation :O2 is determined by 1. O2 dissociation curve2. Spectrophotometry

1. Left-to-right Intracardiac Shunts - Oximetry run


• O2 saturation by spectrophotometry :– Based on Beers law – Advantages : quick ,accurate, precise , subject to few

errors , less dependency on Hb% .– Disadvantages :

Inaccurate if large amounts of carboxy hemoglobin is presentIndocyanin green interfere with light source of

spectrphotometryElevated bilirubin effect absorbtion of light


• O2 saturation by spectrophotometry :– Disadvantages :

1% error at 95% O2 saturation2.5% error at 70% O2 saturationMore accurate at 40-50%Low values O2 saturation is not at all reliable if necessary

saturations below 50% can be determined by blood gas method


O2 saturation spectrophotometry is presently best method for oximetry

Procedure of oximetry run• 2-mL sample from each of the following locations.

1. Left and/or right pulmonary artery & Main pulmonary artery2. Right ventricle, outflow tract, mid & tricuspid valve .3. Right atrium, low or near tricuspid valve , mid & high .4. Superior vena cava, low (near junction with right atrium).5. Superior vena cava, high (near junction with innominate vein).6. Inferior vena cava, high (just at or below diaphragm).7. Inferior vena cava, low (at L4-L5).8. Left ventricle.9. Aorta (distal to insertion of ductus).


Procedure of oximetry run• In performing the oximetry run, an end-hole catheter (e.g.,

Swan-Ganz balloon flotation catheter) or one with side holes close to its tip (e.g., a Goodale-Lubin catheter) can be used

• The entire procedure should take less than 7 minutes.• If a sample cannot be obtained from a specific site because of

ventricular premature beats, that site should be skipped until the rest of the run has been completed.


site Average Range

SVC 74% 67-83%

IVC 78% 65-87%

RA 75% 65-87%

RV 75% 67-84%

PA 75% 67-84%

LA 95% 92-98%

LV 95% 92-98%

FA 95% 92-98%


• IVC variation

• RA variation

• SVC and IVC difference

• Oxygen saturation abnormalities :– Right heart saturation 1. Elevated PA saturation – high cardiac output , L to R shunt2. Low PA saturation – low cardiac out put , low systemic

arterial saturation , increased oxygen extraction . – Left heart saturation

1. Elevated FA saturation – Pt.receiving O22. Low FA saturation – lung disease , pulmonary edema , R

to L shunt



Limitations of Oximetry Method1. A primary source of error may be the absence of a steady

state during the collection of blood samples.


Error source Problem solving

Prolonged because of technical difficulties

Start from PCW-PA-RV-RA-VC

If the patient is agitated (children)

Sedation

If arrhythmias occur during the oximetry run

Leave the site and go to next site

Limitations of Oximetry Method2. Antman and coworkers , oxygen

saturation influenced by the magnitude of systemic blood flow. – High levels of systemic flow

tend to equalize the arterial and venous and low levels increase difference.


Limitations of Oximetry Method3. Antman and colleagues , the influence of blood hemoglobin

concentration may be important when blood O2 content (rather than O2 saturation) is used to detect a shunt


Limitations of Oximetry Method4. Lacks sensitivity in detecting intracardiac shunts , Small shunts,

however, are not consistently detected by this technique.5. Variations in pulmonary venous saturation– Lower portion of lung has lower O2 saturation– Children CHD – atelectasis – compress the bronchus –

desaturation of corresponding bronchus6. d/t the presence of physiological shunt– Thebesian veins and coronary veins entering LV (R- L) – Bronchial veins draining in to LA / PV (R- L) – Bronchial artery to pulmonary artery (L – R )


7. Various CHD where it is virtually impossible to calculate systemic and pulmonary blood flow– In a patient with a large L-R shunt caused by arterial

collaterals entering the distal pulmonary vascular bed , it is impossible to obtain a blood sample distal to the shunt



• Selective angiography is effective in visualizing and localizing the site of left-to-right shunts

• Angiographic demonstration of anatomy has become a routine part of the preoperative evaluation of patients with congenital or acquired shunts and is useful in localizing the anatomic site of the shunt

Left-to-right Intracardiac Shunts - AngiocardiographyShunt by cardiac catheterization


Lesion View Angio site

ASD Steep LAO (60) cranial(15) PA angio - levophase

VSD LAXO(60-30) –Perimembranous and mid muscular 4CV(LAO40-40) – posterior muscular and inlet RAO(30) – Anterior muscular and outlet

LV angio

PDA Lateral , LAO(60) , RAO caudal Pulmonary or Aortic angio

AVSD 4CV(LAO40-40) Lv angio

LV – RA 4CV(LAO40-40) Lv angio


Angiograms in the LAXO in VSD


Angiograms in the lateral position in patent ductus arteriosus


Angiograms in the LAO position in RSOV to RA

• Qualitative by oximetry and next Quantitative by flow ratio• Quantification is done by Qp , Qs , Qp/Qs , Effevtive blood flow,

L-R shunt , R-L shunt .• Qp and Qs are amount of blood flowing through pulmonary

and systemic vascular bed• Qef is quantity of mixed venous blood that carries desaturated

blood from systemic capillaries to be oxygenated by lungs• L-R and R-L shunt are amount of blood that bypass systemic

and pulmonary vascular bed .

Shunt by cardiac catheterizationLeft-to-right Intracardiac Shunts - Flow ratio

• Qp , Qs , Qeff are based on Ficks principle for calculation of cariac output

• Cardiac output = VO2 / AVO2 difference


• Points of importance while calculation:

1. Oxygen consumption2. Calculation of saturations3. Oxygen content



• Oxygen consumption:– Emperical formulas :

• VO2 = 125 * BSA• For boys, VO2 = 138.1 - 11.49 In(age) + 0.378 (heart rate).• For girls, VO2 = 138.1 - 17.04 In(age) + 0.378 (heart rate).

• Calculation of saturation :– PAO2 and FAO2 are usually calculated by blood samples– MVO2 and PVO2 calculations are most important– MVO2


• MVO2 at atrium level

1. At rest = 3SVC + IVC / 4Flamm's formula weights blood returning from the superior vena cava more heavily than might be expected on the basis of relative flows in the superior and inferior cavae.

2. During bicycle ergometry = SVC + 2IVC / 33. Directly taking SVC saturation as MVO2


• Calculation of saturation PVO2– NOT usually entered – LA vs PVO2


Assumed valve if not calculated

FA saturation

≥ 95% < 95%

Take FA sat.

1. d/t R – L shunt assume 98% as PVO22. Not d/t R – L shunt take FA

saturation

• Oxygen content :– Oxygen in blood is present bound to Hb and dissolved

content– Oxygen content = O2 with Hb + O2 dissolved– O2 with Hb = 13.6 * Hb in gm/dl * % saturation– O2 dissolved = 3.26mlO2/L at oxygen tension of 100 mm hg– Importance of dissolved oxygen – while breathing room air

and breathing oxygen– Eg: oxygen tension is 50 mm hg – O2 dissolved is 1.83 oxygen tension is 500 mm hg – O2dissolved is 16.3


• Additional information that can be obtained are – Bidirectional shunt – Double left to right shunt


• Bidirectional shunt : estimation and quantification of each L-R and R-L shunts can be done by oxymetric help in catheterisation


L – R = Qp – QeffR – L = Qs – QeffNET SUNT = (L-R) – (R-L)

• Double left to right shunt : Not only identification but also quantification double L-R shunt can be done by oxymetry

• Method 1: S = F * A – B /C – A S = L – R shunt in to the chamberF = Blood flowing in to the chamberA = O2 sat. In chamber receiving shunted bloodB = O2 sat. in chamber proximal to the shuntC = O2 sat. in pulmonary vein


• Double L – R shunt – Method 2 :1. Calculate L – R shunt(Qp – Qeff) by convention 2. Calculate L – R shunt of proximal chamber assuming

PAO2 to be saturation in that chamber3. See the difference between step 1 and 2


• PVR = PA – PCWP / Qp• SVR = AORTA – RA /Qs• PVRI = PA – PCWP / CARDIAC INDEX = (PA – PCWP / Qp) * BMI• PVRI/SVRI• Reversibility testing when required

1. MAP > 40 mm hg2. PVRI > 8 wood units3. PVRI/SVRI > 0.5

Left-to-right Intracardiac Shunts - Hemodynamic overloadShunt by cardiac catheterization

Any patient with cyanosis or arterial desaturation <95%

Shunt by cardiac catheterizationSuspicion Of Right to Left Intracardiac Shunts

Supine position of the patient - Alveolar hypoventilation , Excessive sedation from the premedication

COPD or other pulmonary parenchymal diseasePulmonary congestion secondary to the cardiac disease , L – R shunt

Assume a more upright posture , take deep breaths , cough Administer 100% oxygen

Persisting hypoxia indicates L – R cardiac shunt

Shunt by cardiac catheterizationDetection Of Right to Left Intracardiac Shunts

Various methods available in cahteterisation for R – L

1. Indicator dye dilution technique and other indicators2. Angiography 3. Oximetry run

Catheterisation aims in R – L shunts are1. Detection 2. localisation 3. magnitude of shunt

• The site of right-to-left shunts may be localized if blood samples can be obtained from a PV , LA , LV , and Aorta

• The PV blood of patients with arterial hypoxemia caused by an intracardiac right-to-left shunt is fully saturated with oxygen.

• The site of a right-to-left shunt may be localized by noting which left heart chamber is the first to show desaturation .(STEP DOWN).

• By calculation of Qeff quantification of total R – L can be determined by Qs – Qeff

Shunt by cardiac catheterization2. Left-to-right Intracardiac Shunts - Oximetry

Disadvantages of oxymetry in R – L shunt:1. The main disadvantage of this technique is that a PV and the LV

must be entered. This is not as easy in adults as it is in infants, in whom the LA is entered routinely by way of the foramen ovale.

2. Quantification of desaturation that’s significant has not been adequately determined like L – R shunt.

Shunt by cardiac catheterization2. Left-to-right Intracardiac Shunts - Oximetry

• Angiography helps in assessing appropriate anatomy in patients with R – L shunt.

Shunt by cardiac catheterization1. Left-to-right Intracardiac Shunts - Angio cardiography

Retrograde LV angiogram demonstrates a solitary malaligned

VSD

Infundibular narrowing & R-L shunt into aorta is seen in the

RV angio in RAO

Right & anterior AO connected to right-sided (anterior) morphologically RV and left & posterior pulmonary artery (PA) connected to left-sided (posterior) morphologically left ventricle



DORV with side-by-side great artery relationship and subaortic subpulmonic and doubly commited VSD

PVR

• Vascular resistance is the resistance that must be overcome to push blood through the circulatory system and create flow.

• the resistance offered by the pulmonary circulation is known as the pulmonary vascular resistance (PVR)

• Units for measuring vascular resistance are dyn·s·cm−5 or pascal seconds per cubic metre (Pa·s/m³) or mmHg·min/l

• Pulmonary vascular resistance 20–130 dyn·s/cm5 or 2–13 MPa·s/m3 or 0.25–1.6 mmHg·min/l or Woods unit

PVR =80 x (mean PAP – mean PCWP)/ Qp

Non invasive method:PVR = TRV/TVIRVOT woods unit

Date post:	13-Apr-2017
Category:	Health & Medicine
Upload:	mashiul-alam
View:	49 times
Download:	3 times

Ffr, raf, shunt calculation, pvr

Health & Medicine