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

Abstract

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&#xb1;0.35 &#x3bc;V and 98&#xb1;12 beats/min, respectively. They increased within 1 week after MI to 6.91&#xb1;1.91 &#x3bc;V (P=.007) and 107&#xb1;10 beats/min (P=.028), respectively. ScNS reduced aSGNA to 3.46&#xb1;0.44 &#x3bc;V (P<.039) and 2.14&#xb1;0.50 &#x3bc;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&#xb1;6.31 &#x3bc;V&#xa0;(P=.005) and 10.82&#xb1;7.86 &#x3bc;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%&#xb1;11.54% of ganglion cells in the left stellate ganglion and 15.94%&#xb1;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.