Assessment of left ventricular dyssynchrony in patients with heart failure and normal QRS duration.

Cardiac resynchronization therapy (CRT) is an important component of heart failure therapy in patients with a left ventricular ejection fraction <35%, class III or ambulatory class IV symptoms, and a QRS duration >120 ms. The QRS duration criterion for patient selection is imperfect. About 30% of patients with an increased QRS duration are nonresponders to CRT and many with a normal QRS duration with mechanical dyssynchrony respond to CRT. The authors review the currently available echocardiographic tools for the assessment of ventricular dyssynchrony in patients with heart failure.