Mechanical Effects on Right Ventricular Function From Left Bundle Branch Block and Cardiac Resynchronization Therapy

OBJECTIVES The purpose of this study was to investigate how LBBB and CRT modify RV free wall function by direct ventricular interaction. BACKGROUND Right ventricular (RV) function influences prognosis in patients with left bundle branch block ('LBBB) and function. METHODSresynchronization therapy (CRT). There is, however, limited insight into how LBBB and CRT affect RV function. METHODS In 24 patients with LBBB with nonischemic cardiomyopathy, RV and left ventricular (LV) strain by speckle intracking echocardiography was measured before and after CRT. Underlying mechanisms were studied 16 anesthetized dogs with ultrasonic dimension crystals and micromanometers. RESULTS Patients with LBBB demonstrated distinct early systolic shortening in the RV free wall, which.coincided with the typical abnormal early systolic sePtal shortening. animals, this RV free wall contraction pattern resulted reduced myocardial work as a large 1portion of the shortening occurred against low pressure during early systole, coinciding with abnormal leftward septal. motion. RV systolic function was maintained by vigorous contraction in the late -activated LV lateral wall, which pushed the septum toward the RV. CRT reduced abnormal septal motion and increased RV free wall work because there was less inefficient shortening against low pressure. CONCLUSIONS ILBBB reduces workload on the RV free wall because of abnormal septal. motion and delayed activation of the LV lateral wall. Restoring septet and LV function by CRT increases workload in RV free wall and may explain why patients with RV failure respond poorly to CRT. (Contractile Reserve in Dyssynchronyi A Novel Principle to Identify Candidates for Cardiac Resynchronization Therapy [CRID-CRT]; NCT02525185) (J Am Coll Cardiol Img 2020;13:1475-84) (C) 2020 by the American College of Cardiology Foundation.