BackgroundLeft ventricular (LV) diastolic dysfunction is a prominent feature of hypertrophic cardiomyopathy (HCM). Prediction of LV filling pressure using the ratio between early diastolic transmitral flow and mitral annular velocity (E/e') had proved a good accuracy.Aim of this studyWe investigated the value of E/e' to predict cardiovascular (CV) mortality in patients with HCM.MethodsA total of 243 patients with HCM had E/e' measured in combination with clinical evaluation, conventional echocardiographic measurements, cardiopulmonary exercise evaluation, and Holter monitoring.ResultsDuring a mean follow‐up of (3.2 ± 1.2 years), 17 (7%) patients died. Non survivors had significantly higher SBP, DBP, left ventricular outflow tract obstruction (LVOTO) gradient, mitral E, and E/e', but lower e' of mitral annulus and more prevalent restrictive filling pattern. E/e' was directly correlated with age (r = .24, P < .005), left atrial volume index (r = .44, P < .0001), LVMI (r=0.23,P<.005), LVOT gradient (r = .43, P < .0001), NYHA class (r = .19, P < .006), pulmonary artery pressure (r = .24, P < .005), positive family history of HCM (r = .22, P < .005), and inversely related to peak systolic velocity (S) (r = .44, P < .0001). By multivariate analysis, only LVOTO ([RR] 4.11, 95% CI 1.002 to 1.148, P < .04) and E/e' were independent predictors for overall mortality in HCM (relative risk [RR] 5.27, 95% CI 1.002 to 1.024, P < .02). The risk of dying increased with increasing E/e' ratio, being approximately 4 times higher for patients in the highest quartile (HR 3.8 (CI 1.38‐5.12, log‐rank < 0.002)).ConclusionsIn hypertrophic cardiomyopathy, the E/e' ratio remains a powerful predictor of all‐cause mortality, particularly if it is associated with LVOT obstruction.