NEW YORK (Reuters Health) – The benefit of cardiac resynchronization therapy (CRT) in patients with heart failure depends on their QRS interval; CRT does not reduce adverse clinical events in those with a QRS less than 150 milliseconds, according to the results of a meta-analysis reported in the Archives of Internal Medicine online June 13.

“These results have implications regarding patient selection for this important treatment technique,” advise Dr. Ilke Sipahi, with Case Western Reserve University School of Medicine in Cleveland, Ohio and colleagues.

Originally, guidelines indicated CRT for patients with systolic heart failure, New York Heart Association (NYHA) class 3 or 4 symptoms, and a QRS duration of 120 milliseconds or greater, the authors explain.

When it became apparent that many patients with these parameters did not benefit from CRT, revised guidelines recommended CRT in NYHA 1 or 2 systolic heart failure with a new QRS cutoff of greater than 150 milliseconds and continued to recommend CRT for patients with NYHA 3 or 4 heart failure with the old QRS cutoff of 120 milliseconds or greater.

However, the team points out, some studies indicate that CRT does not benefit patients with a QRS duration between 120 and 150 milliseconds, regardless of their NYHA functional class.

The researchers therefore performed a meta-analysis of five randomized CRT trials involving a total of 5813 patients to see if the degree of QRS prolongation affects the impact of CRT on adverse events.

They defined a QRS duration of less than 150 milliseconds as moderately prolonged and a QRS duration of 150 milliseconds or greater as severely prolonged.

They found that patients with severely prolonged QRS randomized to CRT had a 40% risk reduction in a composite of adverse clinical events that included all-cause mortality and heart failure hospitalization (RR = 0.60; p<0.001). Conversely, there was no significant benefit of CRT on adverse events in patients with moderately prolonged QRS (RR = 0.95; p=0.49).

However, Dr. Sipahi and colleagues caution that because they did not have access to patient-level data, “The exactitude of the 150-millisecond cutoff observed in the current analysis for predicting clinical benefit with CRT is likely to be imperfect for the individual patient.”

Reference:
Impact of QRS Duration on Clinical Event Reduction With Cardiac Resynchronization Therapy
Arch Inter Med 2011.