Dynamic relationship of left-ventricular dyssynchrony and contractile reserve in patients undergoing cardiac resynchronization therapy

Aims Contradicting reports have been published regarding the relation between a dobutamine-induced increase in either cardiac dyssynchrony or left-ventricular ejection fraction (LVEF) and the response to cardiac resynchronization therapy (CRT). Using apical rocking (ApRock) as surrogate dyssynchrony parameter, we investigated the dobutamine stress echocardiography (DSE)-induced changes in left-ventricular (LV) dyssynchrony and LVEF and their potential pathophysiological interdependence. Methods and results Fifty-eight guideline-selected CRT candidates were prospectively enrolled for low-dose DSE. Dyssynchrony was quantified by the amplitude of ApRock. An LVEF increase during stress of 5 was regarded significant. Scar burden was assessed by magnetic resonance imaging. Mean follow-up after CRT implantation was 41 13 months for the occurrence of cardiac death. ApRock during DSE predicted CRT response (AUC 0.88, 95 CI 0.770.99, P 0.001) and correlated inversely with changes in EF (r 0.6, P 0.001). Left-ventricular ejection fraction changes during DSE were not associated with CRT response (P 0.082). Linear regression analysis revealed an inverse association of LVEF changes during DSE with both, total scar burden (B 2.67, 95CI 3.77 to 1.56, P 0.001) and the DSE-induced change in ApRock amplitude (B 1.23, 95 CI 1.53 to 0.94, P 0.001). KaplanMeier analysis revealed that DSE-induced increase in ApRock, but not LVEF, was associated with improved long-term survival. Conclusion During low-dose DSE in CRT candidates with baseline dyssynchrony, myocardial contractile reserve predominantly results in more dyssynchrony, but less in an increase in LVEF. Dyssynchrony at baseline and its dobutamine-induced changes are predictive of both response and long-term survival following CRT.