Cardiac resynchronization therapy (CRT) is one of the most exciting new advances in the treatment of chronic severe (NYHA symptom class) heart failure associated with dyssynchronous ventricular contraction that is refractory to medical treatment. In all randomized trials CR has resulted in improved NYHA symptom class, exercise capacity and quality of life in the majority of patients as compared to patients on optimal medical therapy including angiotensin converting enzyme inhibitor (ACE)/angiotensin receptor blocker inhibitor (ARB) and b adrenergic receptor blockers. These symptomatic benefits are mediated by reverse remodeling of the left ventricle, that is reduction in volume, regression of LV mass, improvement in ejection fraction and severity of mitral regurgitation induced by synchronization of ventricular contraction. This new text is edited by 5 experts in heart failure, electrophysiology and non-invasive cardiac imaging and is extensively illustrated with high quality figures and examples of clinical cases. The purpose of the book is to put into perspective this novel therapy with regards to traditional heart failure treatment and to provide criteria for identifying patients likely to have an optimal and sustained response to CRT using a practical how to approach. This text begins by describing the background and evolution of the technique to the current implementation and the impact of complications on clinical outcome. There are chapters describing cutting edge Doppler echocardiography for assessing dyssynchrony, reverse remodeling and triaging patients into those with greatest likelihood of responding to CRT with illustrative clinical case examples. There is a full description of the results of all the randomized clinical trials and a number of chapters discussing the need for concomitant internal cardiac defibrillator (ICD), special circumstances such as atrial fibrillation, right bundle branch block, left ventricular lead placement and etiology of heart failure with clinical case examples for each.