Regional heterogeneity in cardiac sympathetic innervation in acute myocardial infarction: relationship with myocardial oedema on magnetic resonance

Purpose To assess the relationships between myocardial structure and function on cardiac magnetic resonance (CMR) imaging and sympathetic tone on I-123-metaiodobenzylguanidine (I-123-MIBG) scintigraphy early after myocardial infarction (MI). Methods Ten patients underwent I-123-MIBG and Tc-99m-tetrofosmin rest cadmium zinc telluride scintigraphy 4 +/- 1 days after MI. The segmental left ventricular (LV) relative radiotracer uptake of both Tc-99m-tetrofosmin and early I-123-MIBG was calculated. The day after scintigraphy, on CMR imaging, the extent of ischaemia-related oedema and of myocardial fibrosis (late gadolinium enhancement, LGE) was assessed. Accordingly, the extent of oedema and LGE was evaluated for each segment and segmental wall thickening determined. Based on LGE distribution, LV segments were categorized as "infarcted" (56 segments), "adjacent" (66 segments) or "remote" (48 segments). Results Infarcted segments showed a more depressed systolic wall thickening and greater extent of oedema than adjacent segments (p < 0.001) and remote segments (p < 0.001). Interestingly, while uptake of Tc-99m-tetrofosmin was significantly depressed only in infarcted segments (p < 0.001 vs. both adjacent and remote segments), uptake of I-123-MIBG was impaired not only in infarcted segments (p < 0.001 vs. remote) but also in adjacent segments (p=0.024 vs. remote segments). At the regional level, after correction for Tc-99m-tetrofosmin and LGE distribution, segmental I-123-MIBG uptake (p < 0.001) remained an independent predictor of ischaemia-related oedema. Conclusion After acute MI the regional impairment of sympathetic tone extends beyond the area of altered myocardial perfusion and is associated with myocardial oedema.