Cardiac-resynchronization therapy (CRT) has known benefits in patients with severe left ventricular systolic dysfunction and prolonged QRS duration (>120 ms).  However, up to half of patients with systolic dysfunction appear to have left ventricular dyssynchrony by echocardiographic measures, despite a QRS duration of less than 120 ms.  As a result, CRT is often used for patients with echocardiographic evidence of dyssynchrony and a narrow QRS complex, despite a lack of clear benefit to this approach.  The Echocardiography Guided Cardiac Resynchronization Therapy (EchoCRT) study sought to determine the effect of CRT on patient outcomes in the setting of symptomatic heart failure, echocardiographic findings of dyssynchrony, and QRS duration <120 ms.

In this multicenter double blind trial, patients with severe symptomatic left ventricular failure (EF<35% and NYHA class III or IV) with a QRS duration of <130ms (mean 105ms) and evidence of dyssynchrony either on tissue Doppler or speckle tracking echo parameters, were all implanted with CRT devices with ICDs and then randomized so that half of study participants had the CRT function turned off.  The primary outcome was a composite of all cause death or hospitalization for heart failure.  Following a pre-planned interim analysis, the study was terminated prematurely after recruitment of 809 out of a planned 1132 patients due to futility.  By study close, 116 patients in the CRT group had met the primary outcome as opposed to 102 in the control group (28.7% vs. 25.2%; HR, 1.20; 95% CI, 0.92 to 1.57; P=0.15).  Device related adverse events were also much more common in the CRT group (P=0.003), largely driven by lead displacements.  Most worryingly of all, mortality was significantly increased in the CRT group (45 deaths vs 26 deaths, HR, 1.81; 95% CI, 1.11 to 2.93; P=0.02).

Conclusions

CRT is not beneficial, and may cause significant harm, in patients with severe systolic heart failure and a narrow QRS.  These findings raise questions about the importance of echocardiographic measures of mechanical dyssynchrony.  Further, patient selection for CRT should remain based on current ECG criteria.

• Ruschitzka F, Abraham WT, Singh JP, Bax JJ, Borer JS, Brugada J, Dickstein K, Ford I, Gorcsan J 3rd, Gras D, Krum H, Sogaard P and Holzmeister J.  Cardiac-resynchronization therapy in heart failure with a narrow QRS complex. N Engl J Med. 2013 Oct 10;369(15):1395-405.