Cardiac sympathetic nerve activity in the non-infarcted region in patients with a prior myocardial infarction and left ventricular remodeling

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Left ventricular (LV) remodeling is observed as LV cavity expansion with wall hypertrophy in the remote non-infarcted region in the LVs after myocardial infarction (MI) and is closely involved in systolic heart failure. Accordingly, we assessed the mechanism of this issue from the viewpoint of cardiac sympathetic nerve function in such a region in 16 patients with a prior myocardial infarction using positron emission tomography (PET) and radiolabelled catecholamine analogue 11C-hydroxyephedrine (HED) as a marker for neuronal catecholamine uptake function. HED retention index was determined by normalizing myocardial tracer activity from 30 to 40 minutes to the integral of the 11C activity input function. Cardiac presynaptic catecholamine uptake is known to depend on myocardial blood flow. Thus, we quantitatively measured regional myocardial blood flow （MBF) using PET with 13N-ammonia on the same day. LV volumes were also determined using echocardiography. This study protocol was also do … More ne in 10 healthy volunteers served as normal controls. Results: LV end-diastolic volume index was significantly larger in patients with a prior MI than in normal controls (69.6±15.9 vs 47.2±13.4 ml/m2, p<0.01). An apparent LV remodeling was observed in patients with a prior MI. In normal controls, myocardial blood flow and HED retention index were largest in the LV anterior wall. MBF was significantly less in the remote non-infarcted region in patients with a MI compared with that in the anterior wall in normal controls (0.76±0.14 vs 0.88 ± 0.13 ml/g/min, p<0.05). The retention index of HED (8.06±1.22 vs 7.03 ±1.12 %/min, p<0.01) and the retention index corrected by the blood flow in the corresponding area (10.8± 1.7 vs 8.1± 0.9 %/min/MBF, p<0.001) were significantly higher in the remote non-infarcted region than in the anterior wall of normal controls.Conclusion: A greater amount of sympathetic presynaptic catecholamine uptake is observed in the remote non-infarcted region in patients with a prior MI compared with that in controls. This finding suggests that hyperactivity of myocardial sympathetic nerve function in patients with a prior MI and LV remodeling is related to the pathophysiology of systolic heart failure. Less