Association between left ventricular regional sympathetic denervation and mechanical dyssynchrony in phase analysis: A cardiac CZT study

Purpose: To evaluate the relationships among myocardial sympathetic innervation, perfusion and mechanical synchronicity assessed with cardiac cadmium-zinc-telluride (CZT) scintigraphy. Methods: A group of 29 patients underwent an evaluation of myocardial perfusion with 99mTc- tetrofosmin CZT scintigraphy and adrenergic innervation with 123I-metaiodobenzylguanidine (MIBG) CZT scintigraphy. The summed rest score (SRS), motion score (SMS) and thickening score (STS), as well as the summed 123I-MIBG defect score (SS-MIBG), were determined. Regional tracer uptake for both 99mTc-tetrofosmin and 123I-MIBG was also calculated. Finally, the presence of significant myocardial mechanical dyssynchrony was evaluated in phase analysis on gated CZT images and the region of latest mechanical activation identified. Results: Significant mechanical dyssynchrony was present in 17 patients (59 %) and associated with higher SRS (P=0.030), SMS (P<0.001), STS (P=0.003) and early SS-MIBG (P=0.037) as well as greater impairments in left ventricular ejection fraction (P<0.001) and end-diastolic volume (P<0.001). In multivariate analysis a higher end-diastolic volume remained the only predictor of mechanical dyssynchrony (P=0.047). Interestingly, while in the whole population regional myocardial perfusion and adrenergic activity were strongly correlated (R=0.68), in patients with mechanical dyssynchrony the region of latest mechanical activation was predicted only by greater impairment in regional 123I-MIBG uptake (P=0.012) that overwhelmed the effect of depressed regional perfusion. Conclusion: Left ventricular mechanical dyssynchrony is associated with greater depression in contractile function and greater impairments in regional myocardial perfusion and sympathetic activity. In patients with dyssynchrony, the region of latest mechanical activation is characterized by a significantly altered adrenergic tone. © 2013 Springer-Verlag Berlin Heidelberg