Chapter 8  ·  Module 7

Ventricular Arrhythmias and Sudden Cardiac Death Prevention

Acute management, ACLS pharmacology, channelopathies, and the ICD vs. drug decision

Acute Ventricular Tachycardia and ACLS Pharmacology

Hemodynamically Stable Ventricular Tachycardia

Pharmacologic Termination

  • Procainamide IV -- preferred first-line; Class Ia mechanism; most effective for acute termination; avoid if corrected QT interval over 500 ms or severe left ventricular dysfunction
  • Amiodarone IV -- alternative; preferred in structural heart disease or ventricular tachycardia refractory to procainamide; less hemodynamic risk in impaired ventricle
  • Unstable at any point -- immediate synchronized direct-current cardioversion; do not delay for drugs

Pulseless Ventricular Tachycardia / Ventricular Fibrillation -- ACLS

Shock First; Drugs Are Adjuncts

  • Defibrillation is primary -- drugs do not replace shocks
  • Epinephrine every 3 to 5 minutes -- vasopressor; improves coronary perfusion pressure; improves return of spontaneous circulation but not neurologic survival
  • Amiodarone -- first-line antiarrhythmic after 3rd shock (shock-refractory ventricular fibrillation)
  • Lidocaine -- equivalent alternative to amiodarone (ALPS trial finding); use when amiodarone unavailable

Channelopathies -- Drug Selection and Avoidance

Syndrome Trigger Treatment Drugs to Avoid
Brugada Syndrome Rest, sleep, fever ICD (proven therapy); quinidine for ventricular fibrillation storm and shock reduction; isoproterenol IV for acute storm (bridge to quinidine) Sodium channel blockers (flecainide, propafenone, procainamide); tricyclic antidepressants; cocaine
Long QT type 1 Exercise, swimming Beta-blockers (nadolol or atenolol) -- highly effective; ICD if breakthrough events All QT-prolonging drugs; sympathomimetics
Long QT type 2 Sudden auditory stimuli, emotional arousal Beta-blockers (moderately effective); mexiletine adjunct; silence alarm sounds All rapid repolarizing potassium channel-blocking drugs (Class Ia, Class III, certain antibiotics, antifungals, antipsychotics)
Long QT type 3 Rest, sleep, bradycardia Mexiletine (blocks persistent late sodium current -- the type 3 defect); ICD strongly recommended; beta-blockers limited benefit Class Ia and Ic sodium channel blockers; amiodarone; other QT-prolonging agents
Catecholaminergic polymorphic ventricular tachycardia Exercise, emotional stress, sympathomimetics Nadolol first-line (non-selective, never stop abruptly); flecainide adjunct when nadolol insufficient; ICD if prior arrest Sympathomimetics; abrupt beta-blocker withdrawal

Sudden Cardiac Death Prevention -- ICD vs. Pharmacology

Primary Tool

Implantable Cardioverter-Defibrillator

  • Only intervention proven to reduce sudden cardiac death in primary prevention
  • Primary prevention threshold: ejection fraction 35% or less + New York Heart Association Class II to III + 3 months optimal medical therapy (SCD-HeFT criteria)
  • Secondary prevention: standard of care after survived cardiac arrest or hemodynamically significant ventricular tachycardia
  • Adjunct drugs (beta-blockers, amiodarone) reduce shock burden but do not replace the device

Pharmacologic Role

What Drugs Can and Cannot Do

  • Beta-blockers ONLY -- sole antiarrhythmic class with proven mortality benefit (post-myocardial infarction, heart failure with reduced ejection fraction, long QT type 1, catecholaminergic polymorphic ventricular tachycardia)
  • Amiodarone -- effective for acute ventricular arrhythmias and ICD shock reduction; NO primary prevention mortality benefit (SCD-HeFT)
  • Neurohormonal agents (ACE inhibitors, mineralocorticoid antagonists) -- reduce sudden cardiac death via reverse remodeling, not direct antiarrhythmic effects
  • Antiarrhythmic drugs are adjuncts to ICD -- not alternatives to it

The SCD-HeFT Teaching Point

The Sudden Cardiac Death in Heart Failure Trial (2005) definitively established that amiodarone provides no primary prevention mortality benefit compared to placebo in patients with heart failure with reduced ejection fraction. Amiodarone's efficacy for treating acute arrhythmias does not translate into a survival advantage as a primary prevention strategy. The ICD -- not amiodarone -- is the primary prevention tool. Beta-blockers are the only antiarrhythmic class that reduces mortality in primary prevention.