Prognostic Implications of ‘Paced’ and ‘Native’ QRS Durations Following Cardiac Resynchronization Therapy

Abstract

Current evidence strongly suggests that the extent of electrical dyssynchrony within the left ventricle is determined by the delayed intraventricular conduction time reflected by a prolonged QRS duration (QRSd) on the surface (ECG). However, in cardiac resynchronization therapy (CRT) follow-up algorithms, the QRSd on the post-operative ECG has been relatively less frequently addressed, although the baseline QRSd is accepted as an essential ‘pre-operative’ marker for patient selection and prediction of response to therapy. In this review, we discuss the clinical impact of post-implantation electrocardiographic parameters, such as the ‘paced’ QRSd and ‘native’ QRSd (assessed when the device is temporarily switched off) on the efficacy of therapy and on prediction of future outcomes after CRT.