November 7, 2007–ORLANDO–Cardiac resynchronization therapy (CRT) failed to provide any clinical benefit in heart failure (HF) patients with a “narrow” QRS interval and evidence of left ventricular mechanical dyssynchrony (1), the results of the Resynchronization Therapy in Normal QRS (RethinQ) trial reveal.
CRT did not increase the primary endpoint—improved six-month oxygen consumption at peak exercise capacity—beyond that with standard treatment. There was a significant improvement in New York Heart Association (NYHA) class with CRT, but lead RethinQ investigator John Beshai, MD, (University of Chicago, Illinois, USA) was quick to point out that this was not consistent with other secondary endpoint results, and that NYHA class is an unreliable measure.
The results were presented by Beshai at the American Heart Association Annual Scientific Sessions in Orlando, Florida, and simultaneously published online by the New England Journal of Medicine.
CRT is indicated in HF patients with a left ventricular ejection fraction (LVEF) of 35 percent or less, a New York Heart Association (NYHA) class of III or IV, and a QRS duration of 120 milliseconds (ms) or more. A QRS below 120 ms is considered normal.
Beshai’s team studied 172 patients. All patients received an ICD, and 85 were randomly assigned to also receive CRT. Among 156 patients analyzed for the primary endpoint at six months, 46 percent of CRT compared with 41 percent of the control group achieved an improvement in oxygen consumption, as measured by cardiopulmonary exercise stress testing. However, the difference was not significant. There were no improvements in either quality of life or six-minute walk distance with CRT.
Colleagues recommended further investigation “in larger, stronger, and longer randomized studies with outcome measures.”
Sources: http://www.heartwire.com, http://money.cnn.com, http://www.sjm.com
(1) Ventricular dyssynchrony can occur when synchronous beating of the heart is disturbed and ventricles pump less efficiently. Many patients with advanced heart failure exhibit ventricular dyssynchrony. It often is seen as a wide QRS complex with a left bundle branch block morphology on an electrocardiogram (ECG).