Cardiac-resynchronization therapy (CRT) reduces morbidity and mortality in chronic systolic heart failure with a wide QRS complex. Mechanical dyssynchrony also occurs in patients with a narrow QRS complex, which suggests the potential usefulness of CRT in such patients.
New data, from a randomized trial, presented at the European Society of Cardiology (ESC) 2013 Congress (also published in the New England Journal of medicine) concluded that cardiac resynchronization therapy (CRT) will not improve outcomes in patients with narrow QRS intervals (i.e. <130 ms) and have evidence of ventricular dyssynchrony by echocardiographic criteria. In fact, it may actually increase the risk of cardiovascular death.
This randomized trial involving 115 centers to evaluate the effect of CRT in patients with New York Heart Association class III or IV heart failure, a left ventricular ejection fraction of 35% or less, a QRS duration of less than 130 ms, and echocardiographic evidence of left ventricular dyssynchrony. All patients underwent device implantation and were randomly assigned to have CRT capability turned on or off. The primary efficacy outcome was the composite of death from any cause or first hospitalization for worsening heart failure.
At study closure, the 809 patients who had undergone randomization had been followed for a mean of 19.4 months. The primary outcome occurred in 116 of 404 patients in the CRT group, as compared with 102 of 405 in the control group (28.7% vs. 25.2%; hazard ratio, 1.20; 95% confidence interval [CI], 0.92 to 1.57; P=0.15). There were 45 deaths in the CRT group and 26 in the control group (11.1% vs. 6.4%; hazard ratio, 1.81; 95% CI, 1.11 to 2.93; P=0.02).
– The primary end point had occurred in 218 patients with no significant difference between the two groups; however, there was a significant mortality increase in the CRT-on group (p=0.02).
– There was no significant difference in changes in NYHA class from baseline to six months, nor were there differences in quality of life by the Minnesota Living with Heart Failure Questionnaire.
– About 19% of CRT-on and 15.6% of CRT-off patients received ICD shocks, and significantly more CRT-on patients had inappropriate shocks, 5.0% vs 1.7% (p=0.01).
The authors concluded that in patients with systolic heart failure and QRS duration of less than 130 ms, CRT does not reduce the rate of death or hospitalization for heart failure and may increase mortality.
These findings shut down hopes that the usefulness of CRT might be extended to heart failure patients without significant QRS prolongation who have echo evidence of ventricular dyssynchrony.
The results of this study reinforce the notion that, at least until new methods of assessment are developed, QRS width (with or without mechanical dyssynchrony) remains the primary determinant of response to CRT. These data also suggest that CRT use in patients with QRS duration of less than 120 ms is unwarranted, could be harmful, and should not be considered. It also argues against the use of echocardiographic criteria for trying to identify patients with < 130 ms QRS duration who might respond to CRT.
– Frank Ruschitzka, M.D., William T. Abraham, M.D., Jagmeet P. Singh, et al. Cardiac-Resynchronization Therapy in Heart Failure with a Narrow QRS Complex. NEJM; September 3, 2013DOI: 10.1056/NEJMoa1306687