Relationship between QRS duration and left ventricular dyssynchrony in patients with end-stage heart failure.

Patients with end-stage heart failure and a wide QRS complex are considered candidates for cardiac resynchronization therapy (CRT). However, 20% to 30% of patients do not respond to CRT. Lack of left ventricular dyssynchrony may explain the nonresponse. Accordingly, we evaluated the presence of left ventricular dyssynchrony using tissue Doppler imaging (TDI) in 90 consecutive patients with heart failure. Ninety patients with severe heart failure (left ventricular ejection fraction <35%, New York Heart Association class III-IV) were prospectively evaluated. Based on QRS duration, 30 consecutive patients with a narrow QRS complex were included (QRS duration 150 ms). All patients underwent TDI to assess left ventricular dyssynchrony. Extensive left ventricular dyssynchrony was defined as an electromechanical delay on TDI between the septum and lateral wall, the so-called septal-to-lateral delay, of >60 ms. Severe dyssynchrony was observed in 27% of patients with narrow QRS complex, 60% with intermediate QRS duration, and 70% with wide QRS complex. No relation existed between QRS duration and septal-to-lateral delay. From 30% to 40% of heart failure patients with QRS duration >120 ms do not exhibit left ventricular dyssynchrony, which may explain the nonresponse to CRT. Alternatively, 27% of patients with heart failure and a narrow QRS complex show significant left ventricular dyssynchrony and may be candidates for CRT.