Inappropriate shock delivery by implantable defibrillators with dual chamber pacing during nonsustained ventricular tachycardia in patients with heart block.

Transvenous implantable cardioverter defibrillators (ICDs) have improved the management of patients with ventricular tachycardia/ventricular fibrillation (VT/VF). Many patients with sustained VT/VF have bradyarrhythmias and nonsustained VT. Shock delivery due to nonsustained VT would be an undesirable feature. Abortive shock capability (noncommitted shocks) is a feature available in devices to prevent delivery of shocks for nonsustained VT. Recently, the availability of dual chamber pacing capability has improved the efficacy of ICDs by obviating the need of separate pacemaker implantation in patients with VT/VF and concomitant bradyarrhythmias. However, interaction between bradyarrhythmias and VT/VF has not been described and has important clinical implications. We report a case in which a patient with complete atrioventricular (AV) block and ventricular arrhythmias received an inappropriate shock following spontaneous termination of nonsustained VT, showing an important shortcoming of devices with these features.