Abstract 655: Clinical Characteristics of Patients Experiencing Inappropriate Shocks from Primary Prevention ICDs: Findings from the PROSE-ICD Registry
Introduction Despite the efficacy of implantable cardioverter defibrillators (ICD) for the prevention of sudden death in patients with dilated cardiomyopathy, inappropriate shocks are not uncommon and are associated with an increased risk of mortality. We investigated the characteristics of patients experiencing inappropriate shocks in the PROSE-ICD registry, a multicenter prospective study of individuals with dilated cardiomyopathy undergoing prophylactic ICD implantation.
Methods and Results In a case cohort analysis of 545 patients enrolled at Johns Hopkins University, individuals having received an ICD shock for nonventricular tachyarrhythmias were compared to a random sampling of the entire cohort. Of all individuals enrolled (age: 62±14 years, 25% female, 22.4% atrial fibrillation (AF), 54.7% ischemic cardiomyopathy (ICM)), 82 patients experienced an ICD shock over an average follow-up of 270 ± 260 days. Of those who were shocked, 38 experienced therapy secondary to AF (73.7%), atrial/sinus tachycardia (23.7%) or lead noise (2.6%). This represented 42.6% of all shock therapies experienced. Patients experiencing inappropriate ICD therapies were more likely to have a higher body-mass index (28.9 vs. 25.6, p=0.01), better renal function (GFR 87.2 vs. 77.0, p=0.04), and have a VT zone programmed with a lower shock cutoff rate (175bpm vs. 183bpm, p=0.026). The presence of ICM (HR 0.324, CI 0.162– 0.646) and increased levels of BUN (HR 0.936, CI 0.893– 0.981) reduced the likelihood of an inappropriate therapy while persistent (not paroxysmal) AF (HR 2.92, CI 1.4–5.98) increased the likelihood of an inappropriate shock. Although there were no differences between the presence or absence of an atrial lead or specific device manufacturers, activating supraventricular tachycardia (SVT) discriminators actually increased the likelihood of inappropriate therapies (HR 2.52, CI 1.3– 4.88).
Conclusions Inappropriate ICD shocks comprise a large percentage of all ICD therapies delivered during the early period after device implantation, most of them the result of AF. The presence of an atrial lead did not reduce the risk of an inappropriate shock. Utilizing SVT discrimination algorithms actually increased the risk of an inappropriate shock.