Both low and high energy cardioversion induced accelerated ventricular tachycardia in a patient treated with an implantable cardioverter defibrillator

A 72-year old male with an old myocardial infarction who had drug-refractor y ventricular tachyarrhythmias received an implantable cardioverter-defibri llator (ICD). The patient did not take his prescribed beta-blocking agent f or two days, following which he experienced six discrete shocks for spontan eous VT while riding his bicycle. Both 5J and 30J cardioversions were ineff ective at terminating the VT and accelerated VT developed following the sho cks. After admission, an electrophysiological study was performed while he was taking the P-blocking agent, both low and high energy cardioversions re producibly terminated the clinical VT without showing any accelerated rhyth m. These findings suggest that the increase in sympathetic discharge may en hance the proarrhythmic potential of ICDs.