Comparison of clinical benefits and outcome in patients with programmable and nonprogrammable implantable...

Technological advances in implantable cardioverter defibrillators (ICDs) have provided a variety of programmable parameters and antitachycardia therapies whose utility and impact on clinical outcome is presently unknown. ICDs have capabilities for cardioversion defibrillation alone (first generation ICDs), or in conjunction with demand ventricular pacing (second generation ICDs), or with demand pacing and antitachycardia pacing (third generation ICDs). We examined the pattern of antitachycardia therapy use and long-term survival in 110 patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF). Group I included 62 patients with nonprogrammable first generation ICDs that delivered committed shock therapy after ventricular tachyarrhythmia detection based on electrogram rate and/or morphology was satisfied. Group II included 48 patients with multiprogrammable ICDs (including second and third generation ICDs) that had programmable tachyarrhythmia detection based on rate and tachycardia confirmation prior to delivery of electrical treatment with either programmable shocks and/or, as in the third generation ICDs, antitachycardia pacing. Incidence and patterns of antitachycardia therapy use and long-term survival were compared in the two groups. The incidence of appropriate shocks in patients who completed 1 year of follow-up was significantly greater in group I (30 of 43 patients = 70% vs 11 of 26 patients = 42%; P less than 0.05). In the total follow-up period, a significantly larger proportion of group I patients as compared to group II patients used the shock therapies (46 of 62 patients = 74% vs 25 of 48 patients = 52%; P less than 0.01), with the majority doing so within the first year of implantation (96% and 92%, respectively). Although the frequency of antitachycardia therapy activation was similar, the number of shocks delivered per patient was lower in group II, particularly in the initial 3 months of follow-up (P = 0.06). No clinical variable aided in identifying users from nonusers of antitachycardia therapy. Arrhythmic mortality was virtually eliminated in both groups. Two-year actuarial cardiac survival in the two groups was similar (group I = 78% vs group II = 84%; P greater than 0.2). Survival from cardiac mortality in users and nonusers of antitachycardia therapies was also similar in both groups (P greater than 0.2) and in the total patient group (P greater than 0.2). We conclude that programmable ICDs continue to confer advantages in prevention of sudden death that were observed with nonprogrammable ICDs and can be expected to improve patient tolerance and physician acceptance of device therapy for VT/VF.