CRT Does Not Benefit Patients with Narrow QRS and Echocardiographic Dyssynchrony

The positive effects of cardiac resynchronization therapy (CRT) on mortality and morbidity are seen in patients with QRS durations longer than 120 msec regardless of heart failure (HF) class but are more pronounced in patients with left bundle branch block and wider QRS. Clinical trials have failed to demonstrate a significant benefit of CRT in patients with QRS shorter than 120 msec (NEJM JW Cardiol Nov 14 2007; see also Circ Arrhythm Electrophysiol 2013;6:538 and Circulation 2013;127:873). However, since left ventricular (LV) dyssynchrony is associated with worsening of congestive HF, logic suggests that even in patients with narrow QRS, CRT could improve outcomes in those with echocardiographic evidence of dyssynchrony.

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