In patients with hypertrophic cardiomyopathy (HCM), the low positive predictive accuracy of the previously recognised risk factor for sudden death—that is, non-sustained ventricular tachycardia, syncope, abnormal blood pressure response to exercise, family history of sudden death, and massive left ventricular (LV) hypertrophy—is a major limitation.^1–5 Patients with a combination of two or more sudden death risk factors have been recently identified as higher risk group.^1,2,4 Extreme LV hypertrophy > 30 mm does not appear to be a single key determinant of sudden death.^2,4 In searching for other morphological substrates that culminate in the above mentioned sudden death risk factors, we hypothesised that a small LV cavity may appear as a predictor of sudden death because it is commonly associated with several risk factors for sudden death: syncope,⁵ abnormal blood pressure response to exercise, and massive LV hypertrophy.^3,4

To assess the cumulative effect of increased septal hypertrophy and decreased LV cavity size we used the proportion of two echocardiographic parameters measured at end diastole (the ratio of septal thickness to left ventricular diastolic diameter (S/LVDd)). The aim of the study was to compare sudden death rate between patients with …