By Anthony J. Brown, MD

NEW YORK (Reuters Health) – New research suggests that more than 92% biventricular pacing provides optimal outcomes for heart failure patients who receive cardiac resynchronization therapy (CRT). The extent to which higher levels of pacing improve outcomes depends on whether an atrial arrhythmia is present.

Prior research has shown that CRT can decrease mortality and heart failure hospitalizations, but the best degree of biventricular pacing was unclear, lead author Dr. Bruce A. Koplan, from Brigham and Women’s Hospital, Boston, and colleagues note.

To investigate, the research team analyzed data from 1812 patients enrolled in the CRT RENEWAL and REFLEx trials. The subjects were an average of 72 years of age and 72% male. The prevalence of coronary artery disease was 67%.

Relative to 92% pacing was associated with a 44% reduction in the risk of death or heart failure hospitalization, according to the report in the January 27th issue of the Journal of the American College of Cardiology.

The presence of atrial arrhythmia influenced whether higher levels of pacing above 92% further improved outcomes, Dr. Koplan told Reuters Health.

“In patients with no history of atrial arrhythmia, a greater pacing percentage (98% or greater) showed a significant incremental reduction in mortality and heart failure hospitalization compared with pacing 93% to 97%,” he noted. “However, for patients with a history of atrial arrhythmia, pacing incrementally >92% (i.e., 98% to 99% vs. 93% to 97% and 100% vs. 98% to 99%) did not further reduce the risk of HF hospitalization and all-cause mortality.”

Subgroup analysis found that patients with a history of atrial arrhythmia were less likely than those without this history to receive greater than 92% pacing, the report shows.

“The most important question for future CRT studies is why there remain a high proportion of non-responders,” Dr. Koplan said. “The subcategories of this question are: Are we choosing some patients incorrectly? Can we do a better job with appropriate lead location? Can we do a better job with device programming? Or all of the above?”

Reference:
J Am Coll Cardiol 2009;53:355-360.