The Guidelines Committee of the Heart Failure Society of America has updated its recommendations after reviewing the latest evidence. The recommendations, published in the February issue of the Journal of Cardiac Failure, now recommend that cardiac resynchronization therapy (CRT) should also include larger patient groups with mild heart failure symptoms.

A CRT device operates by synchronizing the function of the left ventricle by stimulating the part of the ventricle with a delayed contraction to contract more efficiently and more coordinated, which results in the heart becoming more efficient and ultimately improving the risk of morbidity, survival chances and the patient’s quality of life.

The use of these devices, whether alone or in combination with an implantable cardioverter defibrillator (ICD) is supported by substantial evidence for the use in patients with moderate or severe heart failure, i.e. heart failure that is categorized as class III or class IV according to the New York Heart Association classification system, whilst newer research has studied the impact of the treatment in those with less severe symptoms.

After the committee reviewed three large randomized clinical trials of CRT, in patients with mild heart failure symptoms and various meta-analyses, which assessed using CRT irrespective of the severity of symptoms, senior researcher, Randall C. Starling, MD, MPH, of the Department of Cardiovascular Medicine at the Cleveland Clinic declared:

“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. The evidence is most compelling among patients with an electrocardiogram QRS duration ≥ 150 ms (normal being

According to the Guidelines Committee CRT is now recommended for patients in sinus rhythm with a widened QRS interval ≥ 150 that is not caused by RBBB, whose ejection fraction is reduced and who have persistent mild to moderate heart failure regardless of receiving optimal medical therapy. CRT may also be considered for ambulatory class IV patients with QRS interval ≥ 150 ms and severe LV systolic dysfunction and for those with a QRS interval of ≥ 120 to < 150 ms and severe LV systolic dysfunction, who have persistent mild to severe heart failure, regardless of receiving optimal medical therapy. The recommendations of the QRS thresholds are first and foremost based on evidential subgroup analyses, as well as proven systematic reviews instead on the limits of the eligibility criteria of the trial. Dr. Starling states:
“Subgroup analyses are generally limited by the potential for chance findings. 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.”

HFSA President, Barry Massie, MD adds:

“CRT is still a relatively new technology that seemed to come out of nowhere a few years ago. 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 researchers are aware that a number of evidence gaps need to be addressed, such as the optimum threshold for QRS duration, QRS morphology, degree of myocardial scarring, lead placement, and the best method to assess dyssynchrony. Dr. Starling declares in a concluding statement:

“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.”

Written by Petra Rattue