Cardiac resynchronization therapy: is systole all that matters?

Abstract

Next, the majority of patients recruited in this study had an ischaemic aetiology of heart failure; in these patients, it is mandatory to assess e’ as the average of the two or four basal segments to avoid the effect of regional dysfunction. 4 Surprisingly, the average E/e’ was not significantly improved in these patients, but only septal E/e’ that can be influenced by regional dysfunction typical of ischaemic disease. Another important consideration is that diastolic filling may be significantly influenced by AV interval optimization after CRT. In particular, proper AV setting determines an adequate LV filling without blunting the A wave. The authors partially overcome this limitation performing AV interval optimization in all the patients early after CRT implantation but they did not repeat AV interval optimization 6 months after CRT. This operation may have significant relevance after 6 months because different loading conditions, LV reverse remodelling, and also better LV relaxation/contractility may have changed the AV interval that warrants optimal LV filling. Importantly, this study underscored the relevance of assessing BNP levels: they were related to diastolic indices, tended to be higher in non-responders, and significantly decreased after CRT only in responders. Brain natriuretic peptide levels have already been shown to be well correlated with diastolic function, in particular with LV end-diastolic pressure obtained by invasive measurement. 5 Recently, in a sub-analysis of the CARE-HF (CArdiac REsynchronisation-Heart Failure) trial, BNP levels together with the severity of mitral regurgitation at baseline have been shown to be the most powerful independent predictors of mortality in patients undergoing CRT. 6 Therefore, based on these considerations, the reduction in BNP levels after CRT may be used as an important laboratory marker of a positive CRT response and should be assessed together with clinical and echocardiographic responses. Finally, in order to better clarify the effect of CRT on diastolic function, the next step is to explore the effects of biventricular pacing on diastolic dyssynchrony. Similarly to systolic dyssynchrony, diastolic dyssynchrony may occur in heart failure patients with prolonged QRS duration. Previous studies have shown that systolic and diastolic dyssynchrony assessed with tissue Doppler