Background: The existence of an association between left ventricular (LV) mechanical dyssynchrony and impaired myocardial adrenergic tone has been hypothesized. However, a comprehensive evaluation of the relationships between regional LV perfusion, adrenergic innervation and mechanics is still lacking.
Purpose: To assess the interactions between regional left ventricular (LV) sympathetic innervation, perfusion and mechanical dyssynchrony in patients submitted to low-dose nuclear imaging on a Cadmium-Zinc-Telluride (CZT) camera.
Methods: Eighty-three patients underwent a combined evaluation of LV perfusion and sympathetic innervation at 99mTc-tetrofosmin/123I-metaiodobenzylguanidine (123I-MIBG) CZT imaging. The summed rest score (SRS) and summed 123I-MIBG score (SS-MIBG) were computed as measures of LV perfusion and innervation heterogeneity. The extent of “innervation/perfusion” mismatch was computed as the number of denervated LV segments with relatively preserved perfusion. LV mechanical dyssynchrony (LVD) was evaluated at phase analysis on gated CZT images and the LV wall with the latest mechanical activation identified.
Results: LVD was revealed in 36 (43%) patients. Patients with LVD had lower LV ejection fraction (28±10% vs 54±15%, P<0.001) and more abnormal SRS (21±9 vs 10±8, P<0.001) and SS-MIBG (29±9 vs 17±11, P<0.001) values than those with normal mechanical activation. On a per-patient basis, the presence of LVD was associated with a higher burden of “innervation/perfusion” mismatch (8±4 vs 6±3 LV segments in patients without dyssynchrony, P=0.019).
At wall-based analysis, LV walls with delayed mechanical activation also showed a significantly higher burden of “innervation/perfusion” mismatch (2.3±1.4 segments) than normally contracting walls of patients with LVD (1.7±1.3 segments) and of subjects without LVD (1.3±1.2 segments; P<0.001).
At multivariate analysis, after correction for clinical, LV functional and perfusion variables, the extent of “innervation/perfusion” mismatch was the only predictor of LVD [Odds ratio (OR): 1.34, 95% confidence interval (CI): 1.06–1.67; P=0.012], together with LV ejection fraction [OR: 0.84, 95% CI: 0.77–0.91; P<0.001].
Conclusions: LVD clusters with alterations of regional myocardial perfusion and sympathetic innervation.
Patients with LVD show an elevated burden of “innervation/perfusion” mismatch that is concentrated at the level of the dyssynchronous walls.