ICDs are not for unipolar pacemaker users

Heed these indications and contraindications

Implantable cardioverter defibrillators (ICDs) have proved effective in terminating ventricular arrhythmias in patients who are at risk of sudden death due to their arrhythmias and who have experienced one of the following situations:

· survival of at least one episode of cardiac arrest due to ventricular tachyarrhythmia;

· recurrent, poorly tolerated sustained ventricular tachyarrhythmia;

· recurrent, poorly tolerated sustained ventricular tachycardia.

ICDs have been shown to be more effective for prolonging survival in those patients than drug therapy.

Therapy with ICDs is contraindicated in patients who have:

· a unipolar pacemaker, or a pacemaker that defaults to unipolar mode;

· ventricular tachyarrhythmias that have demonstrated a reversible cause such as digitalis intoxication, electrolyte imbalance, hypoxia, sepsis, or a transient cause attributable to such factors as acute myocardial infarction, electrocution, or drowning.

Therapy may also be contraindicated in patients who have:

· uncontrolled supraventricular tachyarrhythmias with excessive ventricular rates despite conventional drug therapy;

· ventricular tachyarrhythmias that require frequent shocks.