Cardiac resynchronization therapy prognosis

Synonyms and Keywords: CRT
 * : Bhaskar Purushottam, M.D. [mailto:bpurushottam@gmail.com]

Overview
Approximately 30% of patients undergoing CRT will not sustain clinical or functional improvements for a wide variety of reasons.

Non-responders
30% of the CRT recipients are considered "non-responders". A patient is considered a "non-responder" if there is no significant clinical or functional improvement following CRT. There are multiple explanations as to why some patients are non-responders.
 * 1) Not all patients with QRS duration greater than or equal to 0.12 seconds have mechanical dyssynchrony. Unfortunately, the PROSPECT trial which set out to examine the various echocardiographic parameters to predict CRT response was not successful. Some of the major limitations in the study were the technical difficulties in obtaining the dyssynchrony parameters and the discrepancies among the different centers.
 * 2) The leads may have been placed in regions of the left ventricle which are not dyssynchronous
 * 3) The leads may have been placed in regions with fibrosis or viable myocardium.
 * 4) Anterior left ventricular lead placement has been associated with worsening hemodynamics.
 * 5) Non-responsiveness can occur due to high left ventricular capture thresholds
 * 6) Lead dislodgement
 * 7) Long atrioventricular delay
 * 8) Atrial tachyarrhythmias with rapid ventricular response
 * 9) Frequent premature ventricular contractions.
 * 10) Lack of optimal atrioventricular and ventricular to ventricular (i.e., right ventricle to left ventricle) timing can result in non-responsiveness.