Filling the need for new antiarrhythmic drugs to prevent shocks from implantable cardioverter defibrillators.

The implantable cardioverter defibrillator (ICD) has had an enormous impact on the treatment of patients with lifethreatening ventricular arrhythmias. It has been shown not only to be effective in reducing mortality in patients who have survived a potentially life-threatening ventricular arrhythmia (1) but also to improve outcomes when used as primary prevention for sudden cardiac death in patients with ischemic cardiomyopathies (2–4). However, an ongoing problem with ICD therapy is recurrent shocks that occur in some patients. Inappropriate shocks can occur because of problems with the defibrillator lead itself or from supraventricular tachyarrhythmias, most commonly atrial fibrillation (AF). In addition, patients can receive recurrent appropriate shocks for the ventricular arrhythmias for which the ICD was originally implanted. Although such shocks can be life saving, they can be painful and emotionally traumatic for the patient, particularly if they are frequent.