Internal Cardioverter Defibrillator ICD and Antiarrhythmic Drug Interaction

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Internal Cardioverter Defibrillator (ICD) and
Antiarrhythmic Drug Interaction Steven Singh,
M.D.
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Internal Cardioverter Defibrillator (ICD)
The first full human implantation of an
ICD occurred in February 1980. Since then,
ICD technology has become extremely
complex. Current ICDs not only have the ability
to defibrillate, but also to pace, terminate
ventricular tachycardia (VT) and provide back-up
pacing for bradycardia.
continued
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Internal Cardioverter Defibrillator
(ICD) (continued)
Dual chamber pacing with rate response is
also now available. The ICD is extremely
expensive. The total cost with implanting may
exceed 40,000.00.
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Indications for ICD Implantation

• The Class I indications for ICD implantation in
• which a broad consensus exists include
• Cardiac arrest caused by VT or ventricular
  fibrillation (VF) not due to a transient or
  reversible cause
• Spontaneous sustained VT
• Syncope of undetermined origin with clinically
  relevant electrophysiologically inducible
  sustained VT or VF when drug therapy is
  ineffective or not tolerated or not preferred

continued
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Indications for ICD Implantation (continued)

• Non-sustained VT in patients with CAD, prior MI,
  LV dysfunction and electrophysiologically
  inducible VT or VF not suppressed by Class I
  anti-arrhythmic drugs.
• These indications are frequently updated as the
• results of outcome trials become available.

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Antiarrhythmic Drugs (AADs)
AADs are also very complex and become even more
so as newer agents are being developed to affect
specific cardiac channels. The
simplest classification of AADs is the
Vaughn-Williams as seen on the next slide.
continued
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AAD Classifications
Class I Sodium Channel Blockers IA Quinidine,
Procainamide Disopyramide IB Lidocaine,
Mexiletine IC Flecainide, Propafenone Class
II Beta Blockers Propranolol, Metoprolol
continued
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AAD Classifications (continued)
Class III Potassium Channel Blockers Sotalol,
Dofetilide, Amiodarone Class IV Calcium Channel
Blockers Verapamil, Diltiazem, Nifedipine
Amiodarone contains activities of all four
classes, yet it is classified as a Class III
agent.
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AAD Therapy
About 40 to 70 percent of patients with
ICDs require AAD therapy. Indications
concomitant for antiarrhythmic agents in patients
with ICDs are shown on the next slide.
continued
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AAD Therapy (continued)

• Indications include
• To reduce the frequency and duration of sustained
  and non-sustained VT events requiring shocks that
  are painful, and also to avoid battery depletion.
• To slow VT rate to increase efficacy of
  anti-tachycardia pacing (ATP), thus decreasing
  the need for shock therapy.

continued
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AAD Therapy (continued)

• To reduce the frequency and rate of
  supra-ventricular tachycardia (SVT) that can
  cause inappropriate shocks.
• To reduce ventricular rate in SVT to avoid
  inappropriate shocks.
• To reduce sinus rate to avoid inappropriate
  shocks.
• To reduce defibrillation thresholds (DFTs),
  making it easier to defibrillate.

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ICD and AAD Interactions

• Specific ICD and AAD interactions are as follows
• Sodium channel blockers increase energy for
  successful defibrillations.
• Potassium channel blockers decrease DFTs.
• Antiarrhythmic drugs may affect pacing threshold,
  making it more difficult to capture.

continued
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ICD and AAD Interactions (continued)

• Antiarrhythmic drugs may slow rate of VT,
  interfering with sensing rate below the detection
  zone for both ATP and shock.
• AADs may slow dV/dT, thereby prolonging the QRS
  on the ECG with the possibility of double
  counting and inappropriate shocks.

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Effect of AAD Therapy on DFTs
Increase Decrease Variable Lidocaine
Dotalol Procainamide Mexiletine
Dofetilide Propafenone Flecainide
Bretylium Quinidine Disopyramide Moricitine Propra
nolol Verapamil Adapted from Naccarellie GV et
al in Cardiac Electrophysiology from Cell to
Bedside. Tipes and Jalife, 2nd Edition, Saunders
1995, pages 1426-1433.
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Proarrhythmia
AADs can aggravate the clinical arrhythmia.
This is called proarrhythmia. It is more likely
to occur in patients with ischemic heart disease
and decreased left ventricular function. Classifi
cations of proarrhythmia are shown on the next
slide.
continued
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Proarrhythmia Classifications
Antiarrhythmic Drug Proarrhythmia Class I -
Flecainide, Propafenone Sustained VT, slow
atrial flutter rate causing 11
conduction to the ventricle Class II -
Beta blocker Severe sinus bradycardia Class
III - Sotalol, Dofetilide Torsades de
pointes Class IV - Verapamil, Diltiazem Severe
sinus bradycardia