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AICD and Pacemaker UpdateKathryn Gray CRNA
•Excitability: The ability of a cell to respond to a stimulus by depolarizing and propagating an action potential•Depolarization: Occurs when there is a decrease in the polarity across a cell membrane.•Hyperpolarization: Occurs when there is an increase in the polarity across a cell membrane. •Conductivity: The ability of a cell to transmit action potentials to adjacent cells. •Rhythmicity: The ability of cells to generate automatic action potentials.
Terminology:
Card
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Card
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Where it all begins…………
Lets get nerdy… This equation is used to define the electrical
gradient across a membrane based on ion concentrations
This can be applied to cardiac myocytes which helps to explain the ion potentials during AP propagation and RMP.
Ion [Intracellular]
[Extracellular]
Equilibrium potential (Em)
Sodium 10 mM 145 mM 60 mV
Potassium 135 mM 4 mM -94 mV
Chloride 5 mM 120 mM -97 mV
Calcium 0.00000010 mM
2 mM 132 mV
Nernst Equation Em= (-RT/zF) X log [K]i/[K]o
•Em is the equilibrium potential of the ion based on transmembrane concentrations.•R-universal gas constant (8.314472 JXK -1)•T- absolute temperature (273.15 degrees kelvin)•[K]i- potassium concentration on the inside of the cell•[K]o-potassium concentration on the outside of the cell.•z- the number of electric charges carried by a single potassium ion•F- the Faraday constant (9.6485309 X104 cmol-1)
Paging Dr. Nernst
Lets get really nerdy…The Goldman-Hodgkin-Katz equation
accounts for the ionic potentials of multiple ions across a cell membrane.
EMF= 61.5 X log([Na]iPNa+[K]iPK+[Cl]oPCl)
([Na]oPNa+[K]oPK+[CliPCl)
•The SA node is made up of specialized cardiac muscle cells which do not have contractile abilities. •The SA node is the primary pacemaker in the cardiac conduction system. •It’s intrinsic rate is faster than the other latent pacemakers in the heart and thus overrides them.• It’s automaticity and intrinsic rate is dependant upon *calcium leak channels in the sarcoplasmic reticulum.
The Sinoatrial Node
At the cellular level
SA Node conduction
•This is a portion of the heart with a more rapid rate than the sinus node.•Also occurs when transmission from the SA node to A-V node is blocked (A-V block).•During sudden onset of A-V block, sinus node impulses do not get through, and next fastest area of discharge becomes pacemaker of heart beat.•Delay in pickup of the heart beat is called “Stokes-Adams” syndrome. The new pacemaker is in A-V node or penetrating part of A-V bundle.
Ectopic Pacemakers
AV nodeThe AV node contains highly specialized tissue
that slows impulse conduction considerably
thereby allowing sufficient time for complete atrial
depolarization and contraction prior to
ventricular depolarization and contraction.
Purkinje FibersLocated in the inner
ventricular walls of the heart, just beneath the endocardium.
The Purkinje fibers have the fastest conduction speed of any fibers in the heart.
The ventricles
Normal ventricular RMP is -80 to -90mVAction potential is accelerated once threshold is reached by the opening of fast Na channels and slow Ca channels.
Pu
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Depolarization during a cardiac cycle
Excit
ati
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Con
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C
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….
Innervation of the heart
Releases norepinephrine at sympathetic ending
Causes increased sinus node firing rate
Increases rate of conduction impulse
Increases force of contraction in atria and ventricles
Parasympathetic (vagal) nerves, Release acetylcholine at
their endings innervate S-A node and A-
V junctional fibers Causes
hyperpolarization because of increased K+ permeability in response to acetylcholine
Muscarinic Acetylcholine Receptors, when stimulated cause decreased heart rate
Sympathetic Parasympathetic
CNS control of Heart rate
Auto
nom
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ffect
s on C
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Causes of cardiac dysfunction
Temperature extremes pH imbalances Hypo or Hypercalcemia Malnutrition, cachexia Hypoxia/Ischemia Hypo or hyperkalemia Autonomic imbalances Hypo or hypercarbia Magnesium deficiency Drug toxicity and adverse
drug reactions Stress and catecholamine
release
CAD HTN Dilated myopathy Morbid obesity Advanced age CHF Chronic lung disease and
subsequent cor pulmonale Endocrine imbalance Hypertropic myopathy Sick sinus syndrome Increased ICP Renal disease
Physiologic Imbalances Associated Co-motbidities
Types of conduction disruptions - Atrial Fibrillation - Atrial Flutter - 1st degree heart block - 2nd degree heart block - 3rd degree heart block - Ventricular fibrillation - Ventricular tachycardia - Re-entry arrhythmias
The Solution:
And the beat goes on….
Pacemaker coding system
Chamber Paced
Chamber Sensed
Response to Sensing
Programmability
Antiarrhythmia Function
A=Atrium A=Atrium T=Triggered P=SimpleC=Communicating
P=Pacing
V=Ventricles V=Ventricles I=Inhibited R=Rate modulation
S=Shock
D=DualBoth atria and ventrical
D=DualBoth atria and ventrical
D=DualBoth triggered and inhibited
M=Multiprogram
D=DualBoth pacing and shock
O=None O=None O=None O=None O=None
Who gets what?
CODE What is it? Who gets it?
AOO Atrial pace, no sense no inhibitions
SSS with intact conduction in the OR with bovie
AAI Atrial pace, atrial sense, inhibition by the atrium
SSS with intact conduction system
VOO Ventricular pace, no sense no inhibition
Third degree heart block in OR with atrial fibrillation
VVI Ventricular pace, ventricular sense and ventricular inhibition
Third degree heart block with atrial fibrillation
DOO Dual pace, no sense no inhibitions
Third degree heart block in OR with bovie
DVI Dual pace, ventricular sense, ventricular inhibition
Third degree heart block with SVT
DDD Dual pace, dual sense dual inhibit
Third degree heart block
The name is Bond, James Bond
This is a schematic of how each pacemaker will affect the EKG depending on the intrinsic beat and pacemaker mode
Rate Responsive Pacemakers
Rate-Responsive Direct metabolic sensors: 1. Mixed Venous O2 saturation 2. Central venous pH
In-Direct metabolic sensors: 1. Ventilation rate 2. Mixed Venous Temperature
Non-Metabolic Physiological sensors 1. QT interval 2. Ventricular Depolarization Gradient 3. Stroke Volume 4. Mean Arterial Blood Pressure
Direct Activity sensors 1. Motion detection
Pacemaker effects on CO
Anesthesia and in situ pacemakersElectromagnetic interference is
always a problem when taking a person into the OR for a surgical procedure.
Increase in Pacemaker threshold with some drugs in the OR setting.
Physiologic alterations can change pacemaker function.
Questions you need to ask before going into the OR What is the device?
What brand and model? Does your hospital have a programmer for this
make and model? What is the magnet mode? Why does the patient have a pacemaker? What rhythm does the patient have when the
pacemaker is shut off? When was the last time it was interrogated? How long has it been since the battery has been
changed?
AICD’s
Indications for AICD insertionCommon indications for AICD implantation
Class I indications Class II indications
History of prior MI •LVEF < 35% & NYHA class II/III•LVEF <30% & NYHA class I•Hemodynamically unstable•History of VF and VT inducible in the EP lab
•LVEF < 30% or 35% & NYHA class I•Recurrent VF and normal LVEF
Chronic myocarditis, pericardial disease, hypertrophic or infiltrative cardiomyopathy
• History of spontaneous, sustained VF/VT associated with primary pathology
Non-iscemic dilated cardiomyopathy
•History of sustained VF/VT and significant LV dysfunction
•Unexplained syncope & LV dysfunction•Reccurrent VF/VT normal LVEF
Hyoertrophic cardiomyopathy
•History of documented VT/VF
IT DEPENDS!!
What do you do when your patient has an
existing pacemaker or AICD?
•Questions to ask the patient:•Why do they have an AICD? •How long have they had it?•Who is the manufacturer?•When was the last time it was interrogated?•When was the last time they received an AICD shock?•How often do they get shocked?
Anesthesia for patients with AICD’s
Danger in the O.R.
Electrocautery
Bipolar vs UnipolarWhy do we need a grounding pad?
Why are we afraid of bovie with pacemakers and AICD’s?
Electromagnetic interference in the O.R.
Electrocautery MRIESWLDefibrillationMotor evoked potentialsNerve stimulators
Oversensing Cause
Insulation breach Bipolar impedance
Pacemaker oversensing
Pacemaker undersensing
Failure to capture
Innapropriate AICD shock
The Magic Magnet
The magnet IS NOT magical!!!
Don’t be lured in to a false sense of security of “I’ll just put a magnet on it” to fix any problems.
Magnet Mode
The pacemaker mode temporarily switches to VOO in single chamber devices and DOO in dual chamber devices.
Asynchronous pacing delivers output regardless of intrinsic activity
Pacing rate will be 85 bpm for pacemaker battery levels above ERI (elective replacement indicator) and 65 bpm for battery levels below ERI*
When the magnet is removed, the previously programmed mode returns*
Use when:Checking pacemaker battery levelEMI is present (surgery, TENS, etc.)Device troubleshooting (breaking a PMT, assessing capture,
etc.)
What happens when a magnet is applied over a pacemaker?
Magnet Mode What happens when a magnet is placed
over an AICD? If the patient is not pacemaker
dependant…. If the patient is pacemaker dependant…
So what are the recommendations?
De-fasciculation prior to succinylcholine is recommended if the patient has a RR pacemaker
Question the use of Nitrous if the pacemaker is new
Inhalation agents and propofol do not affect pacing thresholds.
What other monitors do I need? YOU DO NOT ALWAYS NEED TO TURN OFF THE
AICD OR PACEMAKER!
Recommendations Atropine should be close at hand if
the patient should have severe bradycardia.
A patient with an AICD or pacemaker should NEVER be sent home without the device being interrogated by a representative of the device’s company if a magnet has been used.
What about ACLS with AICD’s and pacemakers?
Recommendations:
Perioperative management of these patients should be individualized.
The best type of anesthesia for the patient with an AICD or pacemaker depends on the type of surgery and the patient’s co-morbidities
Bipolar is better If using monopolar cautery, place pad close to incision
site and keep bursts to less than 5 seconds. Cardioversion will reset the device If below the umbilicus the risk of EMI is very low with a
pacemaker. Surgery below the umbilicus in the patient with an AICD
may still create risk of innapropriate shock.
Recommendations All volatile anesthetics depress cardiac contractility
by decreasing calcium into cells during depolarization
NEVER TURN OFF A PACEMAKER OR AICD WITHOUT HAVING THE PATIENT HOOKED UP TO EXTERNAL PACING/DEFIBRILLATION PADS!!!!
Important phone numbers Biotronik 800.547.0394 Boston Scientific 651.582.4000 Sorin Ela 800.352.6466 Medtronic 800.328.2518 St. Jude Medical 800.722.3774
Preoperative Recommendations: All patients with pacemakers undergoing
elective surgery should have had a device check as part of routine care within the past 12 months that identifies the required elements specified below.
• All patients with ICDs undergoing elective surgery should have had a device check as part of routine care within the past 6 months.
Emergency recommendations Identify the type of device Determine if the patient is pacing Pacemaker dependent— Yes: pacemaker (not ICD)— Yes: ICD and pacemaker— No: pacemaker (not ICD)— No: ICD and pacemaker What if I need a central line?
Procedure specific recommendations Monopolar electrosurgery CIED evaluated within 1 month from
procedure External cardioversion CIED evaluated prior to discharge or transfer
from cardiac telemetry Radiofrequency ablation CIED evaluated# prior to discharge or transfer
from cardiac telemetry Electroconvulsive therapy CIED evaluated# within 1 month from
procedure unless fulfilling Table 9 criteria Nerve conduction studies (EMG) No additional CIED evaluation beyond
routine Ocular procedures No additional CIED evaluation beyond routine Therapeutic radiation CIED evaluated prior to discharge or transfer from
cardiac telemetry; remote monitoring optimal; some instances may indicate interrogation after each treatment (see
text) TUNA/TURP No additional CIED evaluation beyond routine Hysteroscopic ablation No additional CIED evaluation beyond routine Lithotripsy CIED evaluated# within 1 month from procedure unless
fulfilling Table 9 criteria Endoscopy No additional CIED evaluation beyond routine Xray/CT scans/mammography No additional CIED evaluation beyond
routine #This evaluation is intended to reveal electrical reset. Therefore, an
interrogation alone is needed. This can be accomplished in person or by remote
Pacemaker and AICD policyEach facility should have a
pacemaker and AICD policy. You should find and become familiar with yours.
When dealing with patients who have pacemakers or AICD’s, please use these policies to guide you since these are what you will be measured by if there are any problems.
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References: Kumar, P. (2007). AICD defibrillators. Retrieved
September 26th, 2009 from www.heartonline.org McChance, K.L., Huether, S.E. (2006).
Pathophysiology: The biologic basis for disease in adults and children (5th ed.). Philadelphia, Pennsylvania: Elsevier-Mosby.
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Rooke, A.G. Pacemakers. University of Washington. Retrieved September 26th, 2009 from www.vaanes.org.
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Questions?Thank
You!!!