NEW YORK (Reuters health) – The effects of cardiac resynchronization may be more dramatic in patients with advanced heart failure, but those with less severe symptoms also benefit from the therapy, according to the findings of a systematic review by Canadian researchers.

Writing in the February 15th Annals of Internal Medicine, Dr. Justin A. Ezekowitz, with the University of Alberta in Edmonton, and colleagues explain that guidelines recommend cardiac resynchronization for patients with left ventricular ejection fraction (LVEF) no more than 35%, NYHA class III or IV symptoms, wide QRS duration (>120 msec), and sinus rhythm.

In the current review, the authors examine the risks and benefits of cardiac resynchronization in patients with less symptomatic heart failure, using data from 25 trials involving over 9000 subjects.

Cardiac resynchronization reduced all-cause mortality in patients with NYHA class I or II heart failure (relative risk, 0.83 – 0.80, depending on patient mix), as well as in patients with NYHA III or IV (RR, 0.80 – 0.78), the investigators report.

Similarly, the risk of hospitalization for heart failure was reduced with cardiac resynchronization in patients with less symptomatic disease (RR, 0.71 – 0.69) to a similar degree as in those with more severe symptoms (RR, 0.66 – 0.65).

While NYHA III or IV patients showed improvements in quality of life and the 6-minute walk test with cardiac resynchronization, however, these benefits were not apparent in patients with NYHA I or II heart failure. “This is not surprising given that patients with NYHA I or II heart failure have less symptom burden and impairments in quality of life at baseline,” the authors comment.

Overall, the data indicate that the implant success rate is 94.4%. On the down side, “peri-implant deaths occurred in 0.3%, mechanical complications in 3.2%, lead problems in 6.2% and infections in 1.4% of trial participants.”

Cardiac resynchronization was previously indicated for less than 10% of heart failure patients. “However,” Dr. Ezekowitz and colleagues write, “as our systematic review reveals, the evidence base has evolved substantially since these earlier estimates and cardiac resynchronization may well be indicated now for most of the 40% of individuals with systolic heart failure who have QRS exceeding 120 msec.”

They conclude that establishing criteria for patient selection based on likely benefit “is of vital importance for researchers, clinicians, and policy makers.”

Ann Intern Med 2011.