Interactions between myocardial sympathetic denervation and left ventricular mechanical dyssynchrony: A CZT analysis

BackgroundA correlation between left ventricular (LV) dyssynchrony (LVD) and impaired myocardial sympathetic tone has been hypothesized. We sought to assess the interactions between regional LV sympathetic innervation, perfusion, and mechanical dyssynchrony.MethodsEighty-three patients underwent evaluation of LV perfusion and sympathetic innervation on Tc-99m-tetrofosmin/I-123-metaiodobenzylguanidine (I-123-MIBG) imaging. The summed rest score and summed I-123-MIBG score (SS-MIBG) were computed. The extent of innervation/perfusion mismatch was defined as the number of denervated LV segments with relatively preserved perfusion. LVD was evaluated on phase analysis and the wall with latest mechanical activation identified.ResultsLVD was revealed in 36 (43%) patients. Patients with LVD had more abnormal values of SRS (219 vs 10 +/- 8, P<0.001) and SS-MIBG (29 +/- 9 vs 17 +/- 11, P<0.001) than those without LVD. The presence of LVD also clustered with a higher burden of innervation/perfusion mismatch (P=0.019). On per-wall analysis, LV walls with delayed mechanical activation showed a higher burden of innervation/perfusion mismatch (2.3 +/- 1.4 segments) than normally contracting walls (1.3 +/- 1.2 segments; P<0.001). On multivariate analysis, the extent of innervation/perfusion mismatch was the only predictor of delayed mechanical activation (P=0.029).Conclusions Patients with LVD show an elevated burden of innervation/perfusion mismatch that is concentrated at the level of the most dyssynchronous walls.