Recovery rates of regional sympathetic reinnervation and myocardial blood flow after acute myocardial infarction

Background The implication of an arrhythmogenic role For infarction-induced disruption of regional myocardial sympathetic nerve activity has led to a search for noninvasive methods to study regional Sympathetic nerve activity in patients after infarction. Methods and Results By using positron emission tomography, we measured the time course of myocardial hypoperfusion with [N-13]-ammonia retention and s ympathetic innervation with [F-18]-6-fluorodopamine within the infarct zone in 10 patients at 2 weeks, 3 months, and 6 months after a first-onset Q-wa ve myocardial infarction. The time course For reestablishment of global car diac autonomic function was also determined by measuring the power spectrum of heart rate variability with on autoregressive technique. The average in farct defect size as determined by the fractional uptake of [13N]ammonia wa s 17.22% +/- 5.95% of the left ventricular myocardium. The Fractional uptak e of [F-18']-fluorodopamine in the infarct zone was similar, at 15.83% +/- 4.45% (not significant). There was a significant increase (14% to 15%, P<.0 5) in myocardial blood flow and [F-18]-fluorodopamine uptake to the infarct zone between 2 weeks and 3 months, with no Further change between 3 months and 6 months. However, the average rate of loss (t1/2 hour) of [18F]-fluor odopamine continued to decrease between 2 weeks and 6 months. This parallel ed a continuing fall in the low-frequency to high-frequency autospectral po wer ratio throughout the 6 months after infarction. Conclusions This study demonstrates a modest increase in myocardial blood f low and evidence for sympathetic reinnervation to the infarct zone between 2 weeks and 3 months after acute myocardial infarction. Despite a flow-depe ndent effect on the uptake of [F-18]-fluorodopamine by 3 months, there is a suggestion that restoration of sympathetic activity within the infarct zon e continues between 3 months and 6 months after acute myocardial infarction .