title: Recovery rates of regional sympathetic reinnervation and myocardial blood flow after acute myocardial infarction.
abstract: 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.
  
  
  RESULTS
  By using positron emission tomography, we measured the time course of myocardial hypoperfusion with [13N]-ammonia retention and sympathetic innervation with [18F]-6-fluorodopamine within the infarct zone in 10 patients at 2 weeks, 3 months, and 6 months after a first-onset Q-wave myocardial infarction. The time course for reestablishment of global cardiac autonomic function was also determined by measuring the power spectrum of heart rate variability with an autoregressive technique. The average infarct defect size as determined by the fractional uptake of [13N]-ammonia was 17.22% +/- 5.95% of the left ventricular myocardium. The fractional uptake of [18F]-fluorodopamine in the infarct zone was similar, at 15.83% +/- 4.45% (not significant). There was a significant increase (14% to 15%; P <.05) in myocardial blood flow and [18F]-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]- fluorodopamine continued to decrease between 2 weeks and 6 months. This paralleled a continuing fall in the low-frequency to high-frequency autospectral power ratio throughout the 6 months after infarction.
  
  
  CONCLUSIONS
  This study demonstrates a modest increase in myocardial blood flow and evidence for sympathetic reinnervation to the infarct zone between 2 weeks and 3 months after acute myocardial infarction. Despite a flow-dependent effect on the uptake of [18F]-fluorodopamine by 3 months, there is a suggestion that restoration of sympathetic activity within the infarct zone continues between 3 months and 6 months after acute myocardial infarction.
authors.affiliation: Department of Medicine and Divisions of Cardiology and Nuclear Medicine, McMaster University Faculty of Health Sciences, Ontario, Canada.
authors.forename: E L
authors.initials: EL
authors.lastname: Fallen
authors.forename: G
authors.initials: G
authors.lastname: Coates
authors.forename: C
authors.initials: C
authors.lastname: Nahmias
authors.forename: R
authors.initials: R
authors.lastname: Chirakal
authors.forename: R
authors.initials: R
authors.lastname: Beanlands
authors.forename: L
authors.initials: L
authors.lastname: Wahl
authors.forename: G
authors.initials: G
authors.lastname: Woodcock
authors.forename: M
authors.initials: M
authors.lastname: Thomson
authors.forename: M
authors.initials: M
authors.lastname: Kamath
mesh_terms: D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000503:physiopathology*; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives; D004562:Electrocardiography; D005260:Female; D005462:Fluorine Radioisotopes; D005500:Follow-Up Studies; D006321:Heart / Q000294:innervation*; D006339:Heart Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000000981:diagnostic imaging / Q000503:physiopathology*; D011379:Prognosis; D012039:Regional Blood Flow; D015203:Reproducibility of Results; D013564:Sympathetic Nervous System / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014055:Tomography, Emission-Computed
chemical_list: D005462:Fluorine Radioisotopes; C043437:fluorodopa F 18; D004295:Dihydroxyphenylalanine