Cryoablation of stellate ganglia and atrial arrhythmia in ambulatory dogs with pacing-induced heart failure

Abstract

Background: There is an association between autonomic nerve discharges and atrial arrhythmias (including bradycardia and tachycardia) in ambulatory dogs with pacing-induced heart failure (HF).

Objective: The purpose of this study was to test the hypothesis that stellate ganglia ablation can reduce the incidence of atrial arrhythmias in a canine model of pacing-induced HF.

Methods: Cryoablation of the caudal half of the left and right stellate ganglia and T2-T4 thoracic sympathetic ganglia was performed in six dogs (experimental group). Left upper stellate ganglia nerve activity, vagal nerve activity, and electrocardiogram were continuously recorded using an implanted radiotransmitter.

Results: After 2 weeks of baseline recording, rapid right ventricular pacing (28 +/- 4 days) was used to induce HF. The control group (N = 6) underwent the same procedures except for cryoablation. The experimental group had no episodes of paroxysmal atrial tachycardia (P <.0001 vs control). Cryoablation significantly (P = .0097) reduced prolonged (>3 seconds) sinus pause episodes from 5 +/- 6 to 0 on day 1, from 250 +/- 424 to 11 +/- 11 on day 7, and from 123 +/- 206 to 30 +/- 33 on day 14 after induction of HF. In the experimental group only, vagal nerve activity may occur alone without concomitant stellate ganglia nerve activity. However, these isolated vagal nerve activity episodes did not result in prolonged sinus pause. Histologic studies confirmed successful cryoablation of the caudal half of the stellate ganglia.

Conclusion: Cryoablation of bilateral stellate and T2-T4 thoracic ganglia significantly reduced paroxysmal atrial tachycardia and prolonged sinus pause episodes induced by sympathetic discharges in dogs with pacing-induced HF.

Figure 1

PSP episodes in experimental group. A and B show typical examples of PSP that occurred without and with, respectively, preceding SGNA. No VNA preceded any of the PSP episodes. C shows the 24-hr distribution of PSP episodes at different days after cessation of rapid pacing. There were no PSP episodes at day1.

Figure 2

Autonomic nerve activity and heart rate after cryoablation. A shows modest increase of heart rate during SGNA and VNA activation at baseline. B and C show SGNA and VNA activities, respectively, one day after cessation of rapid pacing. There were no obvious changes of heart rates in response to the isolated SGNA and VNA.

Figure 3

The 24-hr average SGNA and VNA in dogs with cryoablation. Panel A shows a significant circadian variation of the 24-hour SGNA. SGNA at day1 and day 14 were both significantly higher than that at baseline. Panel B shows that VNA had no significant circadian variation either at baseline or during HF. There were no significant differences in VNA between baseline and day 1 or day 14 after cessation of rapid pacing.

Figure 4

HASDA after cryoablation. A shows a premature atrial contraction (arrow) followed by HASDA on both SGNA and VNA at day1 after cessation of rapid pacing in dog#2. B shows the 24-hr distribution of HASDA at baseline and during HF.

Figure 5

Cryoablated left stellate ganglion stained with trichrome (A and C) and with tyrosine hydroxylase (B and D). A and B show the cranial (unablated) portion of the left stellate ganglion. The fibrotic tissues stained blue with trichrome (Panel A). There were surviving ganglion cells (arrows) in both Panels A and B. C and D show the caudal (ablated) portion of the stellate ganglion. There were dense fibrosis and a few surviving sympathetic ganglion cells (arrow) in D. Objective lens: 4X.