Does cardiac resynchronization therapy provide unrecognized benefit in patients with prolonged PR intervals? The impact of restoring atrioventricular synchrony: an analysis from the COMPANION Trial.

BACKGROUND: The influence of PR prolongation on outcomes after cardiac resynchronization therapy (CRT) is uncertain.

OBJECTIVE: To determine whether PR prolongation predicts outcomes in potential CRT candidates and whether CRT benefits these candidates regardless of baseline PR interval.

METHODS: A database of 1520 patients fulfilling criteria for CRT implant (the COMPANION Trial) was examined. Patients assigned to normal (PR < 200 ms) or prolonged (PR ≥ 200 ms) cohorts were compared within the optimal pharmacologic therapy (OPT) and CRT groups regarding an endpoint of all-cause mortality or heart failure hospitalization. CRT was compared with OPT in normal and prolonged PR interval groups. An interaction test was performed to determine whether CRT influenced outcome as a function of PR interval.

RESULTS: PR prolongation was present in 52% of COMPANION subjects. Randomization to CRT was associated with a reduction in the endpoint, but the strength of the association was greater for those with prolonged PR (hazard ratio = 0.54; P <.01) versus normal PR (hazard ratio = 0.71; P = .02) intervals. CRT (vs OPT) was associated with reduction in the endpoint for subjects with normal or prolonged PR intervals. Reduction in relative risk (CRT vs OPT) was 29% (P = .02) for those with normal PR intervals but was 46% (P <.01) for those with PR prolongation. No interaction was detected between PR interval cohort and treatment (P = .17).

CONCLUSIONS: PR prolongation may affect mortality and heart failure hospitalizations in patients with systolic dysfunction, heart failure, and wide QRS complexes. The effect of PR prolongation may be attenuated by CRT.