Biventricular pacing yields superior results than conventional right-ventricular pacing in BLOCK HF trial

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At Heart Rhythm 2013 (4–8 May, Denver, USA), Anne Curtis, chair of the Department of Medicine at the University at Buffalo School of Medicine and Biomedical Sciences, Buffalo, USA, spoke to delegates on the results of the BLOCK HF study, sponsored by Medtronic. The data demonstrated that simultaneously pacing the lower chambers of the heart, or biventricular (BiV) pacing with a cardiac resynchronization therapy (CRT) device, significantly improves heart failure symptoms and quality of life in a subset of heart failure patients.

The results of the study showed a marked reduction in heart failure-related symptoms for patients with atrioventricular block and left ventricular systolic dysfunction at six, 12, 18 and 24 months treated with BiV pacing as opposed to conventional right-ventricular pacing. Additionally, the data revealed a considerable improvement in quality of life among BiV-paced patients at six and 12 months. Primary results from BLOCK HF were recently published in The New England Journal of Medicine.

“These new data add to the growing body of evidence supporting the use of BiV pacing for treating patients who have AV block and left ventricular dysfunction who are indicated under current clinical guidelines for permanent RV pacing with a pacemaker,” said Curtis, lead investigator of the study. “The BLOCK HF findings have previously demonstrated that BiV pacing delays disease progression prevents heart failure-related events and preserves cardiac function in this patient population. The findings presented confirm two additional, yet equally important clinical benefits associated with this innovative therapy – symptom and quality-of-life improvement.”

At six months, 14% more patients randomised to BiV pacing improved compared to patients in the right ventricular arm. Similar positive findings comparing improvement between arms were reported at later points and sustained over a two-year period in the patients who received BiV pacing. Curtis noted that these results were measured using the Packer Clinical Composite Score (CCS), which analyses a patient’s condition as improved, unchanged or worsened using variables including death, heart failure hospitalisation, a patient global assessment questionnaire, and change in symptoms as measured by New York Heart Association (NYHA) heart failure class. Additionally, increased improvement in NYHA heart failure classification with BiV pacing was seen at 12 months post-randomisation.


BiV patients also experienced an average improvement of five points in quality-of-life (QoL) score at six months post-randomisation. These QoL findings, measured by the Minnesota Living with Heart Failure Questionnaire, are based on a more subjective analysis of the ways heart failure affects the physical, emotional, and social dimensions of a patient’s quality-of-life.


Medtronic CRT devices are not currently approved in the USA for patients with atrioventricular block with left ventricular dysfunction; the results from BLOCK HF will serve as the basis for an application to the FDA seeking an expanded indication for this patient population.