Abstract 3394: Unanticipated Long-Term Survival after Cardiac Arrest in Hypertrophic Cardiomyopathy
Introduction. Patients with hypertrophic cardiomyopathy (HCM) who survive cardiac arrest are generally regarded as a high-risk subgroup with a substantial event rate of > 10%/year due to appropriate implantable defibrillator (ICD) interventions.
Hypothesis. Whether this unfavorable clinical course is typical of HCM patients after cardiac arrest over long periods of follow-up or whether the natural history of some patients with HCM after such profound events is paradoxically more benign is unresolved.
Methods. We accessed the Minneapolis Heart Institute Foundation HCM Registry to characterize long-term outcome in 41 patients who initially experienced either cardiac arrest with ventricular fibrillation (n = 22) or an appropriate ICD shock for ventricular tachycardia/fibrillation (n = 19).
Results. Age at initial event was 35 ± 17 years (range 8 to 68); 59% were male. Left ventricular wall thickness was 14 to 45 mm (mean 24 ± 6) and outflow gradients were zero to 104 mm Hg with 21% ≥ 30 mm Hg at rest. Survival after cardiac event ranged 1 to 29 years (mean 8 ± 17). Of particular note, 15 patients (37%) have survived ≥ 10 years and > 20 years in 3 of these patients (7%). Study patients achieved ages 11 to 84 years (mean 43 ± 17) at the time of current follow-up or death. Each of the long-term survivors was asymptomatic or only mildly symptomatic (NYHA class II) at the most recent evaluation. Of the 41 patients with cardiac events, 13 (32%) had ≥ 1 subsequent cardiac arrest or appropriate defibrillation shock, including 2 patients with clusters of 3 events in the initial 2 years, but none in the subsequent 13 or 26 years. Five patients have died of either heart failure or sudden death 3 to 17 years (mean 7 ± 6) after their initial event.
Conclusions. Long-term survival up to more than 25 years is possible following cardiac arrest in HCM. These observations indicate that the arrhythmogenic substrate in HCM is unpredictable and may remain dormant for extended periods of time (or even appear to “burn-out”) in this heterogeneous disease. Recurrent cardiac arrest is not inevitable.