DALLAS — Electrical storms in implantable cardioverter defibrillator recipients are common, unpredictable, and debilitating—and the investigational antiarrhythmic drug azimilide reduces their incidence by up to 55%.
These were the key findings of a secondary analysis of the Shock Inhibition Evaluation With Azimilide (SHIELD) trial presented by Dr. Stefan H. Hohnloser at the annual scientific sessions of the American Heart Association.
SHIELD was a double-blind trial involving 633 patients who received an implantable cardioverter defibrillator (ICD) for secondary prevention of cardiac arrest and were randomized to the novel class III antiarrhythmic agent, azimilide, at 75 or 125 mg/day or to placebo.
The published primary results showed that treatment with azimilide resulted in relative risk reduction of 47%–57% in the combined end point of total all-cause shocks and symptomatic ventricular tachycardia terminated by antitachycardia pacing (Circulation 2004;110:3646–54).
The new prespecified substudy focused on electrical storm, which is defined as the occurrence of three or more separate episodes within a 24-hour period of ventricular tachycardia and/or ventricular fibrillation requiring ICD shock or antitachycardia pacing therapy.
“Electrical storm may, in fact, constitute a medical emergency,” observed Dr. Hohnloser, who is professor of medicine at J.W. Goethe University, Frankfurt, Germany.
He added that before SHIELD, data on electrical storms were sparse and came mostly from uncontrolled clinical observations.
Of the patients in the placebo arm, 27% had at least one episode of electrical storm during the first year after ICD placement, compared with 23% of patients on 75 mg/day of azimilide and 20% of those on 125 mg/day. Low-dose azimilide reduced the overall relative risk of electrical storms by 41%, compared with placebo, while azimilide at 125 mg/day reduced the risk by 55%.
No precipitating cause could be identified in 87% of electrical storm episodes. The remainder was attributed mainly to worsening heart failure or electrolyte disturbances.
In patients who experienced an electrical storm, 80% were rehospitalized within 1 year of receiving their ICD. That rate was 2.2-fold greater than in patients with isolated ventricular tachycardia/ventricular fibrillation and 4.2-fold greater than in individuals who never experienced ventricular tachycardia/ventricular fibrillation.