Subcutaneous nerve stimulation reduces sympathetic nerve activity in ambulatory dogs with myocardial infarction

BACKGROUND Subcutaneous nerve stimulation (ScNS) remodels the stellate ganglion and reduces stellate ganglion nerve activity (SGNA) in dogs. Acute myocardial infarction (MI) increases SGNA through nerve sprouting. OBJECTIVE The purpose of this study was to test the hypothesis that ScNS remodels the stellate ganglion and reduces SGNA in ambulatory dogs with acute MI. METHODS In the experimental group, a radio transmitter was implanted during the first sterile surgery to record nerve activity and an electrocardiogram, followed by a second sterile surgery to create MI. Dogs then underwent ScNS for 2 months. The average SGNA (aSGNA) was compared with that in a historical control group (n = 9), with acute MI monitored for 2 months without ScNS. RESULTS In the experimental group, the baseline aSGNA and heart rate were 4.08 +/- 0.35 mu V and 98 +/- 12 beats/min, respectively. They increased within 1 week after MI to 6.91 +/- 1.91 mu V (P = .007 ) and 107 +/- 10 beats/min (P = . 028) , respectively. ScNS reduced aSGNA to 3.46 +/- 0.44 mu V (P<.039) and 2.14 +/- 0.50 mu V (P<.001) at 4 and 8 weeks, respectively, after MI. In comparison, aSGNA at 4 and 8 weeks in dogs with MI but no ScNS was 8.26 +/- 6.31 mu V (P = .0 05) and 10.82 +/- 7.86 mu V (P = 0002) , respectively. Immunostaining showed confluent areas of remodeling in bilateral stellate ganglia and a high percentage of tyrosine hydroxylase-negative ganglion cells. Terminal deoxynucleotidyl transferase dUTP nick end labeling was positive in 26.61% +/- 11.54% of ganglion cells in the left stellate ganglion and 15.94% +/- 3.62% of ganglion cells in the right stellate ganglion. CONCLUSION ScNS remodels the stellate ganglion, reduces SGNA, and suppresses cardiac nerve sprouting after acute MI.