Assessment of baroreceptor sensitivity and heart rate variability by 123I-MIBG scintigraphy in patients with myocardial infarction

Abstract

PURPOSE The pathophysiologic interrelation of baroreceptor sensitivity (BRS), heart rate variability (HRV) and I~I-MIBG scintigraphy after acute myocardial infarction was analyzed. METHOD Subjects consisted of 15 patients with acute myocardial infarction treated by angioplasty. BRS was defined as a slope of regression line between beat-by-beat systolic blood pressure and RR intervals during phase IV o f V a l s a l v a maneuver. Power of high frequency (HF) component (from 0.15 to 0.4 Hz) was obtained from power spectral analysis of HRV. Washout rate of Iz~I-MIBG was determined from polar map analysis separately from the infarct zone and the non-infarct zone. Infarct zone and left ventricular ejection fraction (LVEF) was determined by gated ~eTc-tetrofosmin SPECT. RESULTS BRS (parasympathetic reflex function) correlated with power of HF component (parasympathetic tone) (r = 0.66, p <0.05). BRS also correlated with LVEF (r= 0.60, p<0.05). Washout rate of ~z31-MIBG in the non-infarct zone (sympathetic activation) well correlated with BRS inversely (r=-0.79, p<0.01) and with LVEF (r=0.80, p<0.001). However, power of HF component didn't correlate with LVEF nor washout rate of ~:~I-MIBG in the non-infarct zone. These results suggested that the autonomic nerve control was disturbed in patients with left ventricular dysfunction after myocardial infarction. The linkage of BRS and a washout rate of ~231-MIBG in the non-infarct zone closely related with LVEF. However, power of HF component was not a sensitive marker for the relation between autonomic nerve function and ventricular dysfunction. CONCLUSION Baroreceptor sensitivity and I~I-MIBG in the non-infarct zone are useful markers of neural disorder from left ventricular dysfunction after acute myocardial infarction. 0-22