Cardiac resynchronization therapy in patients with narrow QRS

[...]we agree that echocardiographic indicators of dyssynchrony can be useful; nonetheless, our data on patients with narrow QRS have clearly demonstrated that the use of pure "clinical" selection criteria (i.e., drug refractoriness, severe HF, low ejection fraction, large diameters) has permitted us to identify patients who can substantially benefit from CRT in the long term.