Expanded Use of CRT Recommended for Mild HF

Based on a review of the latest evidence, the Guidelines Committee of the Heart Failure Society of America (HFSA) now recommends use of cardiac resynchronization therapy (CRT) be expanded to a larger group of patients with mild heart failure symptoms. Recommendations for integrating new evidence into clinical practice appear in the February issue of the Journal of Cardiac Failure.

The ACC/AHA guidelines note there is strong evidence to support the use of CRT to improve symptoms, exercise capacity, quality of life, LVEF, and survival and to decrease hospitalizations in patients with persistently symptomatic HF undergoing optimal medical therapy who have cardiac dyssynchrony (as evidenced by a prolonged QRS duration).

So, CRT with or without an implantable cardioverter defibrillator (ICD) is recommended in patients with class III or class IV HF according to the New York Heart Association (NYHA) classification system. However, the new guidelines from the HFSA are based on recent research investigating the effect of CRT treatment in patients with less severe symptoms.

For example, recently Adabag and colleagues performed a systematic review and meta-analysis of prospective randomized clinical trials of CRT versus ICDs in patients with reduced ejection fraction (EF), prolonged QRS interval, and NYHA functional class I to II HF. Data were combined from five clinical trials, including 4,317 patients with mild-to-moderate HF. All-cause mortality was significantly reduced with CRT compared with ICD (relative risk [RR]: 0.81). This benefit was significant for patients with NYHA functional class II, but not for NYHA functional class I; however, NYHA functional class I patients had an RR of 0.57 for HF hospitalization with CRT. The results, reported in the Journal of the American College of Cardiology confirm the benefits of CRT in minimally symptomatic or asymptomatic patients.

The HFSA committee reviewed other studies, too, and they noted that "The totality of the evidence supports the use of CRT in heart failure patients with reduced left ventricular ejection function (LVEF) across the spectrum of mild to severe symptoms." Senior author Randall C. Starling, MD, MPH, of the Cleveland Clinic noted that "the evidence is most compelling among patients with an electrocardiogram QRS duration ≥ 150 ms (normal being <100 ms)."

New Guidelines
Specifically, the Guidelines Committee determined that CRT is recommended for patients in sinus rhythm with a widened QRS interval ≥ 150 that is not due to RBBB who have reduced ejection fraction and persistent mild to moderate heart failure, despite optimal medical therapy.

CRT may be considered for ambulatory class IV patients with QRS interval ≥ 150 ms and severe LV systolic dysfunction. CRT may also be considered for patients with a QRS interval of ≥ 120 to < 150 ms and severe LV systolic dysfunction, who have persistent mild to severe heart failure, despite optimal medical therapy.

The evidence supporting the QRS thresholds in these recommendations is based primarily on subgroup analyses and systematic reviews rather than on the boundaries of eligibility criteria used in the trial. "Subgroup analyses are generally limited by the potential for chance findings," according to Dr. Starling. "However, the observations that the majority of the benefit exists in the QRS duration ≥ 150 ms subgroup has been a consistent finding across multiple clinical trials, and it has been confirmed in meta-analysis. Therefore, the Guideline Committee agreed that the totality of evidence supported the QRS duration thresholds."

"CRT is still a relatively new technology that seemed to come out of nowhere a few years ago," said HFSA President, Barry Massie, MD. "However, growing evidence leaves little doubt about the value of this technology. Multiple trials have demonstrated that heart failure patients, whose hearts contract in a discordant manner, have more symptoms and poorer survival. The idea that stimulating the heart electrically to improve its efficiency could have a profound effect was greeted with some skepticism but no longer. Multiple trials have demonstrated that this intervention makes patients feel better, prevents hospitalizations, and prolongs survival in heart failure patients. I congratulate the Guideline Committee for taking on this project, reviewing a wide range of data, and making a compelling argument for increased use of this new technology that has a great deal of promise."

The guidelines note that several evidence gaps must be addressed, including the ideal threshold for QRS duration, QRS morphology, lead placement, degree of myocardial scarring, and the best approach to evaluating dyssynchrony. "It is anticipated that the recommendations will evolve to focus on optimizing patient selection and identifying factors that reliably predict a favorable response to CRT, ideally based on criteria that are clinically important to our patients. We envision that this will form the substrate for guidelines to be updated by the Committee," said Dr. Starling.


  1. Stevenson WG, Hernandez AF, Carson PE, et al. Indications for cardiac resynchronization therapy: 2011 update from the Heart Failure Society of America guideline committee. J Card Fail 2012;18:94-106.
  2. Hunt SA, Abraham WT, Chin MH, et al .2009 Focused update incorporated into the ACC/AHA 2005 Guidelines for the Diagnosis and Management of Heart Failure in Adults A Report of the American College of Cardiology Foundation /American Heart Association Task Force on Practice Guidelines Developed in Collaboration With the International Society for Heart and Lung Transplantation. J Am Coll Cardiol 2009;53:e1-e90. http://content.onlinejacc.org/cgi/content/full/j.jacc.2008.11.009
  3. Adabag S, Roukoz H, Anand IS, Moss AJ. Cardiac resynchronization therapy in patients with minimal heart failure: a systematic review and meta-analysis.  J Am Coll Cardiol 2011;58:935-41. http://content.onlinejacc.org/cgi/content/full/58/9/935


Keywords: Ventricular Function, Left, Quality of Life, Heart Failure, Electrocardiography, Hospitalization, Systole, Defibrillators, Implantable, Cardiac Resynchronization Therapy

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