Better patient outcomes gained from biventricular pacing in patients with AV block and reduced pumping function, BLOCK HF trial shows


Results from the BLOCK HF trial have shown that biventricular (BiV) pacing may offer a significant clinical advantage and improved patient outcomes over conventional right ventricular (RV) pacing among patients with left ventricular (LV) systolic dysfunction and atrioventricular (AV) block who are indicated for a pacemaker.

Data were presented at a late-breaking clinical trial sessions of the American Heart Association’s 2012 Scientific Sessions by Anne Curtis, lead study investigator and chair of the Department of Medicine at the University at Buffalo School of Medicine and Biomedical Sciences, Buffalo, USA.

The BLOCK HF (Biventricular versus right ventricular pacing in patients with left ventricular dysfunction and atrioventricular block) trial is sponsored by Medtronic. The CRT devices used in the trial are not approved by the FDA for the patient population studied at this time.

Results from BLOCK HF demonstrate a
26% relative risk reduction in the composite of death, healthcare utilisation visits requiring IV heart failure therapy, and significant increase in left ventricular end systolic volume index (LVESVi) among the patients receiving BiV pacing, meeting the trial’s primary objective. These findings are preliminary, and other secondary endpoints will be evaluated and reported on in the future, announced Medtronic.

The BLOCK HF trial is the first to show better patient outcomes with BiV pacing in patients who have AV block and heart failure, who would typically receive a pacemaker under the current guidelines,” said Curtis. “These data demonstrate the potential for significant, real-world clinical benefits of biventricular pacing in helping delay the onset or worsening of heart failure symptoms in patients with a slow-beating heart.”

“Today, patients are implanted with a traditional pacemaker when they present with AV block and reduced pumping capacity, but BLOCK HF demonstrates that these patients had better outcomes when treated with biventricular pacing via a cardiac resynchronisation therapy device,” said David Steinhaus, vice president and general manager, Heart Failure, and medical director for the Cardiac Rhythm Disease Management business at Medtronic. “Not only did their chance of death or hospitalisation shrink significantly with biventricular pacing, but it potentially slows the overall progression of heart failure, which significantly affects patients’ quality of life.”


BLOCK HF is a prospective, multicentre, randomised, double-blind, controlled trial that evaluated patients with AV block and LV dysfunction (ejection fraction less than or equal to 50%), New York Heart Association (NYHA) Class I, II or III and who met standard indications for ventricular pacing. It enrolled 918 patients from 60 centres in the United States and Canada; of these, 691 patients were randomised to receive either BiV (349) or RV (342) pacing. NYHA class at enrolment consisted of 16% Class I, 57% Class II and 27% Class III. Patients were followed for up to 102 months, with a mean follow-up of approximately 36 months.