We have read with great interest the report by Biagini et al assessing the potential prognostic utility of a transmitral restrictive filling pattern in patients with hypertrophic cardiomyopathy (HC). The investigators state that patients presenting with restrictive filling patterns during initial evaluation or follow-up tend to have a 6-fold greater risk for developing end-stage HC compared to patients without this filling pattern and a 3.5-fold greater risk concerning total HC-related mortality. They presume that the presence of extensive myocardial fibrosis forms the pathophysiologic substrate responsible for the Doppler restrictive filling pattern and the unfavorable prognosis in HC.

It is a common place that the extent of myocardial disarray-fibrosis, predisposing to reentry phenomena and leading to diastolic and progressive systolic dysfunction, is the key pathophysiologic anomaly in HC. Widely recognized clinical risk factors along with other imaging modalities have been introduced to more objectively describe the aforementioned substrate and define the prognosis of such patients. Diastolic function indexes, as measures of subsequent fibrosis-disarray and potential prognostic indicators, have also been used by us in a previous study, in which we proved that patients with HC with transmitral E/septal Ea ratios ≥15 had an almost 4-fold greater risk for sudden death (p <0.001). However, the problem with echocardiographic indexes, especially the conventional ones, is that they are unreliable in predicting clinical outcome in patients with HC, primarily because of their dependence on loading conditions. Echocardiography unquestionably is a valuable tool for the diagnosis and follow-up of patients with HC; nonetheless, newer imaging modalities such as delayed hyperenhancement magnetic resonance imaging should be routinely used, because they detect more accurately myocardial fibrosis and show better predictability.