Cardiac resynchronization therapy: a practical guide for device optimization, part I.

This is the first part of a two-part series on strategies for optimizing the delivery of cardiac resynchronization therapy (CRT), focusing on device-related aspects. There is overwhelming evidence from prospective randomized controlled trials providing consistent and concordant support for CRT in patients with symptomatic heart failure and ventricular dyssynchrony. CRT has consistently improved quality of life, cardiac structure and function, and survival in the majority of patients enrolled in these trials. No longer a consideration for select individuals with heart failure, the 2005 American College of Cardiology/American Heart Association Guidelines for Managing Adults with Chronic Heart Failure now consider CRT a class IA recommendation for stage C patients (QRS duration > or = 120 milliseconds, left ventricular ejection fraction < or = 35%) who remain symptomatic despite optimal medical therapy. However, not everyone experiences clinical improvement from CRT. This article discusses measures that should be considered to ensure proper functioning of a CRT device. A subsequent article will present strategies to optimize patients' responses to CRT.