Heart rate exceeding the upper rate during moderate exercise is an independent predictor for nonresponse to CRT in patients with AF, whereas chronotropic incompetence is a predictor for patients in SR.

Failure to CRT is associated with new-onset AF. Total atrial activation time may be a parameter to predict response in AF patients.

Larger interlead distance on the lateral thoracic X-ray, associated with positioning of the left ventricular lead in the posterior position, is associated with response after 6 months of follow-up. Furthermore, diminishing the septal-to-lateral delay is predictive for response.