Echocardiography in Cardiac Resynchronization Therapy

Abstract

Cardiac resynchronization therapy (CRT) is an established treatment of heart failure patients who remain symptomatic despite optimal medical treatment, have reduced left ventricular ejection fraction and show broad QRS on surface electrocardiogram. Selection of patients who will benefit from CRT remains challenging and is the focus of ongoing research. Cardiac imaging techniques have provided important pathophysiologic data on the mechanism of action of this therapy, and the factors associated with less benefit of CRT. Cardiac dyssynchrony, extent and location of transmural myocardial scar and position of the left ventricular pacing lead are the main determinants of CRT response. Furthermore, CRT pacing settings can be programmed to obtain the maximum benefit from the therapy. Although optimization of CRT with imaging techniques remains controversial, understanding how changes in CRT settings impact on cardiac hemodynamics may help us to select the most appropriate atrioventricular and interventricular delays. This book chapter provides an overview of the recent advances in imaging techniques to select heart failure patients for CRT and summarizes the echocardiographic techniques that can be used for CRT optimization.