In patients with hypertrophic cardiomyopathy (HCM), patient selection for an implantable cardiac defibrillator (ICD) is based on prediction of sudden cardiac death (SCD) risk. Current SCD risk models for patients with HCM include a low left ventricular ejection fraction (< 50%); however, a low-normal ejection fraction (50%–60%) has not been included as a predictive factor. In this issue of Heart, Choi and colleagues,1 report a retrospective study of 1858 patients with HCM (a low-normal ejection fraction in 415) with a median follow-up of 4.09 years. The primary composite outcome of SCD, ventricular tachycardia/fibrillation and appropriate ICD shocks occurred in 1.9%, The risk of the primary endpoint was higher in HCM patients with an ejection fraction <50% compared with those with an ejection fraction >60% (adjusted HR 5.214, 95% CI 1.574 to 17.274) supporting inclusion of low ejection fraction in SCD risk models. Although a low-normal ejection fraction was not predictive of the primary endpoint, an ejection fraction of 50%–60% was associated with a higher risk of hospitalisation for heart failure (aHR 2.457, 95% CI 1.423 to 4.241) and cardiovascular death (aHR 2.641, 95% CI 1.314 to 5.309) (figure 1)

Annualised event rates of the secondary outcomes. Annualised event rates of secondary outcomes, such as hospitalisation for heart failure, cardiovascular death and all-cause death in patients with hypertrophic cardiomyopathy, are classified based on left ventricular ejection fraction (LVEF).

In the accompanying editorial, Rubis2 reminds us that ejection fraction, the simple ratio of stroke volume to end-diastolic volume, measures only the change in chamber volumes, not myocardial function. Possibly, advanced imaging approaches, such as tissue Doppler imaging or speckle tracking echocardiography would reveal more significant myocardial dysfunction in patients with low-normal ejection fraction. Another consideration in risk stratification …