Differential effect of biventricular and right ventricular DDD pacing on coronary flow reserve in patients with ischemic cardiomyopathy.

UNLABELLED: CRT and Coronary Flow Reserve.
BACKGROUND: Cardiac resynchronization therapy (CRT) has become a mainstay in heart failure management. There are also indications that upgrading of existing pacemakers to CRT systems may be of benefit. The aim of this study was to assess the effect of biventricular (BiV), compared with right ventricular (RV), pacing, on coronary flow reserve (CFR), in patients with ischemic cardiomyopathy. METHODS AND
RESULTS: From our database of heart failure patients implanted with BiV pacemakers, 20 patients (10 responders and 10 non-responders to CRT) were randomly selected. Left anterior descending artery coronary flow reserve was measured invasively, under BiV and RV pacing, using intracoronary adenosine to induce hyperemia. In all the 20 patients, there was a significant difference in the pairwise comparison between CFR recorded during BiV and RV pacing (mean difference 0.15, 95% confidence interval 0.07-0.23, P = 0.001). When comparing responders to non-responders, there was a significant difference as to the effect of BiV, compared with RV, pacing on CFR: mean difference (BiV minus RV CFR) was 0.26 ± 0.06 (95% confidence interval 0.13-0.39; P = 0.002), while in non-responders the difference was 0.04 ± 0.03 (95% confidence interval -0.02 to 0.10; P = 0.168).
CONCLUSION: BiV pacing is overall associated to higher CFR, compared with RV DDD pacing. This difference is almost exclusively attributable to the beneficial effect of CRT on coronary flow reserve in CRT-responders. This effect may contribute to the beneficial action of resynchronization in the failing heart and can be viewed in the context of reports of the usefulness of upgrading RV pacemakers to CRT systems.