Abstract 2510: Can changes in Intra-Ventricular Dyssynchrony during Low dose Dobutamine Stress Echo quantify degree of Response to Cardiac Resynchronization Therapy?
Dobutamine Stress Echo (DSE) has been used for prognostic stratification in patients with dilated cardiomyopathy. The presence of contractile reserve, (an increase in left ventricular (LV) ejection fraction (EF) during DSE) has been suggested to be predictive of CRT outcome and LV remodelling. We hypothesize that changes in LBBB-induced intra-ventricular dyssynchrony (IVD) during low dose DSE could be helpful to predict response and reverse remodelling. We studied 40 pre-CRT patients (65 ± 1y, EF: 24 ± 1%, QRS > 120 ms) and assessed CRT response at 6 months follow-up. Clinical response was defined as a NYHA class reduction (> 1) with a fall in BNP > 30% and reverse remodelling as a change in LV end-systolic volume (LVESV) ≥ 10%. We performed in all, a low dose DSE (max 20 mcg/kg/min) using standard parasternal and apical views. The presence of IVD was detected by the occurrence of an abnormal early, fast and short-lived septal motion/thickening during the isovolumic contraction time called a Septal Flash (SF). The amount of radial inward motion was quantified from an anatomical M-mode in the apical 4-chamber view at baseline and peak dose. At baseline, 21/40 pts had IVD and in all (100%) DSE increased dyssynchrony.All responded clinically and echocardiographically after CRT.However, the patients with most pronounced increase in dyssynchrony (9/21 pts, 42%, increase > 50% compared to baseline) displayed the most marked reverse remodelling (mean reduction in LVESV > 30%) and greater fall in BNP (> 50%) after CRT. The remaining patients (19/40 pts) did not show any sign of IVD at rest or with DSE. Among them, only 5 pts responded clinically, with moderate reverse remodelling (mean LVESV -15%), mainly associated with the correction of abnormal atrio-ventricular filling by CRT.
Conclusion: Low dose DSE increases intra-ventricular dyssynchrony and can help identify pts with residual contractile reserve suffering from the direct consequences of LBBB-induced dyssynchrony. The amount of increase in dyssynchrony with DSE also predicted the degree of clinical and echocardiographic response in these patients.