EDITORIAL Cardiac resynchronization therapy: is systole all that matters?

This editorial refers to ‘Clinical and echocardiographic correlates of improvement in left ventricular diastolic function after cardiac resynchronization therapy ’ by H. Aksoy et al., on page 1256 The benefits of cardiac resynchronization therapy (CRT) are the improvement of heart failure symptoms and promotion of left ven-tricular (LV) reverse remodelling, defined as an increase in LV ejec-tion fraction and a decrease in LV volume. Specifically, the rationale for CRT is to restore a more physiological ventricular activation sequence, and to better coordinate atrio-ventricular (AV) timing to improve the LV pump efficiency.1 Therefore, a greater cardiac output after CRT relies not only on improved systolic emptying but also on better diastolic filling. Many studies investigated the effects of CRT on systolic parameters,2 whereas the effect of biventricular pacing on diastole is less clear, and whether it