Implantable cardioverter defibrillators (ICDs) have been developed to treat ventricular tachycardia or fibrillation (abnormal heart rhythms) by electrical shock or by pacing the heart. ICD therapy is established as highly effective for stopping life-threatening arrhythmias, but it does not preclude the use of anti-arrhythmic drugs for prevention and to decrease the frequency of ICD shocks.

The safety and effectiveness of oral azimilide dihydrochloride in reducing the frequency of ICD shocks has been investigated previously in a placebo-controlled study in patients with ICDs. These results need to be confirmed in this larger double-blind, placebo-controlled study with approximately 600 patients.

Inclusion criteria:

• Currently have an ICD implanted
• Have had a documented episode of symptomatic arrhythmias that triggered a spontaneous ICD shock within 180 days of randomization.
• If the ICD implant is recent, the patient must have had a documented episode of sustained arrhythmias or cardiac arrest within 42 days before implantation of the ICD

Exclusion criteria:

• have severe heart failure
• have a current diagnosis of psychosis
• use illicit drugs
• abuse alcohol
• if female, are currently breast feeding, or plan to become pregnant during the study
• are currently taking antiarrhythmic drugs or other drugs that prolong the QTc interval (a measurement taken from the ECG)
• creatinine >2.5 mg/dL (221 mmol/L)
• potassium <4.0 mEq or >5.5 mEq
• have a neutrophil count (ANC) < 100 mL (low count of a type of white blood cell) at time of randomization
• have 2 or more consecutive QTc values >440 msec