COMPARISON OF FREQUENCY OF AGGRAVATION OF VENTRICULAR TACHYARRHYTHMIAS AFTER IMPLANTATION OF AUTOMATIC DEFIBRILLATORS USING EPICARDIAL VERSUS NONTHORACOTOMY LEAD SYSTEMS

The time of onset of 4,471 episodes of ventricular tachycardia (VT) or fibrillation (VF) in 40 of 65 patients with an implantable cardiovert er-defibrillator (ICD) with endocardial defibrillation electrodes (gro up 1) and in 53 of 123 with epicardial defibrillation electrodes (grou p 2) was analyzed to examine whether the incidence of VT/VF immediatel y after surgery is greater than during further follow up and whether t he site of lead placement exerts an influence on the occurence of thes e arrhythmias. Actuarial survival rates free of VT/VF were 77, 65, and 54% at 1, 3 and 6 months, respectively, for group 1, and 84, 66 and 5 2%, respectively, for group 2. The probability of VT/VF was increased only during the first week after surgery; in that week, 12.8% of all p atients had VT/VF, without significant differences between groups 1 an d 2. Until the end of the first month, this percentage increased to 23 %, whereas only 12 to 15% of patients had VT/VF during subsequent mont hs. In 19 patients with third-generation devices capable of terminatin g tachycardias by overdrive pacing, 326 of 412 VT/VF episodes occurrin g in the first week after surgery were terminated by antitachycardia p acing, and only 86 had to be terminated by cardioversion or defibrilla tion. No postoperative exacerbation of inappropriate ICD therapies was observed in any group; 2 to 5% of patients per month received ICD the rapies for atrial fibrillation or sinus tachycardia. Patients who rece ived appropriate ICD therapies in the first week after surgery were at high risk of recurrence of VT/VF. It is concluded that the incidence of VT/VF is high in the immediate postoperative period, possibly owing to a greater level of endogenous catecholamines, independent of the l ead system, which virtually excludes myocardial irritation by the patc h electrodes as a reason for the exacerbation of VT/VF. ICDs should be activated in the operating room to guard this period of high risk. Be cause many tachycardias can be terminated without painful defibrillati ons, antitachycardia pacing should be activated immediately after impl antation.