Syncope and risk of sudden death in hypertrophic cardiomyopathy.

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 (<18, 18 to 39, and > or =40 years). Older patients (> or =40 years of age) with remote episodes of syncope (>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.

The prognostic importance of left ventricular outflow obstruction in hypertrophic cardiomyopathy varies in relation to the severity of symptoms.

OBJECTIVES: The aim of this study was to investigate whether the prognostic importance of left ventricular (LV) outflow obstruction in hypertrophic cardiomyopathy (HCM) is influenced by other predictors of morbidity and mortality. BACKGROUND: It remains unknown whether the effect of outflow obstruction on clinical outcome in HCM is influenced by other determinants of survival. METHODS: We assessed the impact of severity of symptoms, LV wall thickness, atrial fibrillation, and age on the prognostic importance of outflow obstruction in a large HCM population. RESULTS: Of 526 consecutive HCM patients, 141 (27%) had outflow obstruction. During a follow-up of 4.5 +/- 4.1 years, 34 patients died of HCM. The incidence of cardiovascular death was significantly higher among patients with LV obstruction than among those without obstruction (relative risk [RR] = 2.14; p = 0.02). The prognostic power of the outflow gradient changed in relation to severity of symptoms (p = 0.024). At initial evaluation, LV obstruction was a significant predictor of cardiovascular mortality only in New York Heart Association (NYHA) functional class I to II patients (hazard ratio [HR] = 2.38; p = 0.025). During follow-up, at time of development of severe symptoms, the outflow gradient lost its prognostic significance (HR = 1.18; p = 0.66), whereas NYHA functional class III to IV was associated with an eight-fold increase in risk of cardiovascular mortality (HR = 7.90; p < 0.001). CONCLUSIONS: In patients with HCM, the prognostic importance of LV outflow obstruction varies in relation to the severity of symptoms. In patients with mild or no symptoms, obstruction is an important predictor of cardiovascular death. After development of severe symptoms, NYHA functional class becomes the dominant marker of prognosis independently of the presence of an outflow gradient.