VENTRICULAR-TACHYCARDIA INITIATED BY HIGH-ENERGY CARDIOVERSION IN A PATIENT WITH AN IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR

A transvenous implantable cardioverter defibrillator (ICD) was implant ed into a 58 year old woman with idiopathic dilated cardiomyopathy who had drug refractory monomorphic ventricular tachycardia (VT). Antitac hycardia pacing failed to terminate the VT; termination was attempted at 24 J, which was above the defibrillation threshold. When cardiovers ion at 24 J was delivered, VT with a different morphology and slower r ate was reproducibly initiated. At 3 J, however, the original VT was s uccessfully terminated without initiation of the slower VT. A new VT m ay be induced by high energy cardioversion. This may be a manifestatio n of the proarrhythmic potential of ICDs.