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Patients with hypertrophic cardiomyopathy (HC) are reported to have a mortality rate of about 1.0% per year, and those patients without sudden death risk factors and with no or mild symptoms are generally considered to have a benign clinical presentation. However, the risk of sudden death and the outcome in this latter subgroup have not been investigated systematically and remain unresolved. We assessed the risk of sudden death and outcome in 653 consecutive patients with HC without risk factors and with no or mild symptoms. Over a median follow-up of 5.3 years, 35 patients (5.4%) died of HC-related causes. Mean age at death was 46 ± 20 years in patients who died suddenly and 66 ± 15 and 72 ± 9 years, respectively, in patients who died of heart failure or stroke. Event rate was 0.6% per year for sudden death, 0.2% per year for heart failure death, and 0.1% per year for stroke-related death. Sudden death risk was independently and inversely related to age, and risk of heart failure or stroke death was directly related to age (p = 0.020). At 10 years after the initial evaluation, sudden death risk was 5.9%, with sudden death rate being the lowest (0.3% per year) in patients with normal left atrial dimension (≤40 mm). In conclusion, in patients with HC without conventional risk factors and with no or mild symptoms, the risk of sudden death was not negligible, with an event rate of 0.6% per year. Heart failure and stroke-related death were less common and largely confined to older patients. These results underscore the need for a more accurate assessment of the sudden death risk in patients with HC. © 2014 Elsevier Inc. All rights reserved.

Background— The prognostic significance of syncope has not been investigated systematically in hypertrophic cardiomyopathy, and treatment strategies have been based largely on intuition and experience. Methods and Results— We assessed the relationship between syncope and sudden death in 1511 consecutive patients with hypertrophic cardiomyopathy. Unexplained (n=153) or neurally mediated (n=52) syncope occurred in 205 patients (14%). Over a 5.6±5.2-year follow-up, 74 patients died suddenly. Relative risk of sudden death was 1.78 (95% confidence interval 0.88 to 3.51, P =0.08) in patients with unexplained syncope and 0.91 (95% confidence interval 0.00 to 3.83, P =1.0) in those with neurally mediated syncope compared with patients without syncope. In multivariable analysis, the temporal proximity of unexplained syncope to initial patient evaluation was independently associated with risk of sudden death ( P =0.006). Patients with unexplained syncope within 6 months before the initial evaluation showed a 5-fold increase in risk compared with patients without syncope (adjusted hazard ratio 4.89, 95% confidence interval 2.19 to 10.94), a relationship that was maintained throughout all age groups (5 years before initial evaluation) did not show an increased risk of sudden death (adjusted hazard ratio 0.38, 95% confidence interval 0.05 to 2.74). Conclusions— In the present large cohort of patients with hypertrophic cardiomyopathy, unexplained syncope was a risk factor for sudden death. Patients with syncopal events that occurred in close temporal proximity to the initial evaluation showed a substantially higher risk of sudden death than patients without syncope. Older patients with remote syncopal events did not show an increased risk.