Adverse Impact of Delayed Electrical Activation of the Heart and Benefits of Cardiac Resynchronization

Delayed electrical conduction, represented as a wide QRS native conduction, occurs often in patients with heart failure (HF), and this activation delay causes adverse hemodynamics leading to decrease of left ventricular ejection fraction (LVEF). Biventricular pacing is utilized to provide cardiac resynchronization therapy (CRT) and to help alleviate HF symptoms in patients with decreased LVEF and wide QRS complex. This article provides an overview of the adverse hemodynamics of a prolonged QRS complex, reverse remodeling by CRT, evolution in lead placement, and a detailed review of clinical trials and outcomes over the past two decades. Additionally, the most recent patient selection criteria are reviewed and how evidence-based medicine has transpired into current guideline recommendations for CRT. Finally, there is a discussion regarding management of nonresponse to CRT and new device technology.