Septal flash: At the heart of cardiac dyssynchrony.

Cardiac resynchronization therapy (CRT) has been a major step in the treatment of heart failure patients and intraventricular conduction delay. As a considerable number of patients do not respond adequately to CRT, echocardiographic dyssynchrony selection criteria have been proposed to improve CRT response, but these parameters eventually failed to provide superior selection of CRT candidates. In the last decade, an echo-dyssynchrony parameter called "septal flash" was been reported by several investigators and opinion leaders in the field of CRT. This parameter has a strong pathophysiological rationale and was shown to be a robust and predominant predictor of CRT response in recent observational and retrospective studies. We here provide a comprehensive and balanced overview of septal flash and address several important aspects, questions and potential future implications of septal flash in cardiomyopathy and CRT.