Cardiac resynchronization therapy (CRT) has gained widespread acceptance as a safe and effective therapeutic strategy for congestive heart failure (CHF) refractory to optimal medical therapy. The use of implantable devices has substantially altered the natural history of systolic heart failure. These devices exert their physiological impact through ventricular remodeling, associated with a reduction in left ventricular (LV) volumes and an improvement in ejection fraction (EF). Several prospective randomized studies have shown that this in turn translates into long-term clinical benefits such as improved quality of life, increased functional capacity, and reduction in hospitalization for heart failure and overall mortality. Despite these obvious benefits, there remain more than a few unresolved concerns, the most important being that up to one-third of patients treated with CRT do not derive any detectable benefit. There are several determinants of successful delivery and response to CRT, including selecting the appropriate patient, patient-specific optimal LV pacing lead placement, and appropriate post-implant device care and follow-up. This article highlights the importance of collectively working on all of these aspects of CRT to enhance and maximize response.
Cardiac resynchronization therapy, heart failure, biventricular pacemaker, cardiomyopathy
Disclosure: The author has received research grants and lecture and consulting fees from Biotronik, Boston Scientific, Medtronic, Sorin Group, and St Jude Medical.
Received: January 21, 2010 Accepted: February 10, 2010 Citation: US Cardiology, 2010;7(1):61├óÔé¼ÔÇ£6
Correspondence: Jagmeet P Singh, MD, DPhil, Director, Cardiac Resynchronization Therapy Program, Cardiac Arrhythmia Service, Massachusetts General Hospital Heart Center, Harvard Medical School, Boston, MA 02114. E: firstname.lastname@example.org
Cardiac resynchronization therapy (CRT) has achieved widespread approval as a safe and efficient therapeutic strategy for medically refractory congestive heart failure (CHF). The standard indications for CRT include patients with advanced heart failure and evidence of systolic dysfunction (ejection fraction [EF] ├óÔÇ░┬ñ35%), conduction tissue disease (QRS duration ├óÔÇ░─ä120ms), and marked cardiac symptoms (New York Heart Association [NYHA] class III and IV), despite optimal medical therapy.1 CRT and CRT with defibrillator therapy (CRT-D) involve placement of right atrial (RA), right ventricular (RV), and left ventricular (LV) leads, and exert their physiological impact via synchronizing ventricular contraction. This in turn results in improved pumping efficiency, improved LV filling, and a reduction in the extent of mitral regurgitation.2,3 These implantable devices have substantially altered the natural history of patients with heart failure and exert their physiological impact through ventricular remodeling, which occurs over time with a reduction in LV volumes and improvement in EF.
Several prospective randomized studies have shown that this in turn translates into longterm clinical benefits such as improved quality of life, increased functional capacity, reduction in hospitalization for heart failure, and reduction in overall mortality.1,4Despite these palpable benefits, there remain more than a few unresolved concerns, the most important being that up to one-third of patients treated with CRT do not derive any detectable benefit.5 Given the high prevalence, morbidity, and mortality of CHF and the substantial price tag to society both from CHF as a disease and from CRT as a therapy, the importance of maximizing the response of all patients to CRT is evidently immense. There are several determinants of successful delivery and response to device therapy, which include selecting the appropriate patient, patient-specific appropriate LV lead placement, and optimal post-implant device care and follow-up. This article highlights the importance of collectively working on all of these fronts to enhance the response to CRT.
Patient Selection Surface Electrocardiogram and Mechanical Dyssynchrony
After meeting the criteria of compromised LV function and medically refractory heart failure (NYHA >3), patient selection is still driven by the presence of a wide QRS on the surface electrocardiogram (ECG). It is noteworthy that ECG evidence of an intra-ventricular conduction defect, although a surrogate for ventricular dyssynchrony, is not predictive of acute and long-term response to CRT.
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