Targeted M‐Channel Activation in the Left Stellate Ganglion Protects Against Ischemia‐Induced Ventricular Arrhythmias in Canines

Figures

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  Figure 1. An overview of the experimental process on the timeline. We measured the parameters at 3 key time points: (1) baseline, (2) post injection (30 minutes after LSG microinjection of RTG, but pre AMI), and (3) post AMI (measurements taken at 15 and 60 minutes after LADO for different parameters). AMI indicates acute myocardial ischemia; APD, action repolarization duration; APDA, action potential duration alternans; BVR, beat‐to‐beat variability of repolarization; CS, coronary sinus; ERP, effective refractory period; HRV, heart rate variability; JV, jugular vein; LADO, left anterior descending branch occlusion; LSG, left stellate ganglion; NE, norepinephrine; RTG, retigabine; VAs, ventricular arrhythmias; and VFT, ventricular fibrillation threshold.

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  Figure 2. Retigabine reduces the incidence of spontaneous VAs following AMI. A, Representative ECG traces (lead II) after coronary ligation. B, Comparison of Tp‐Te (n=12). C–E, Frequency of VPB and frequency and duration of VT (n=12). F, Incidence of VF (n=12). Values represent the mean±SEM. All measurements were obtained within the first hour post coronary artery ligation. AMI indicates acute myocardial ischemia; Tp‐Te, Tpeak‐Tend interval; VF, ventricular fibrillation; VPB, ventricular premature beats; and VT, ventricular tachycardia.

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  Figure 3. Effect of retigabine on heart rate and heart rate variability indices. A–D, Heart rate, LF power (reflecting primarily sympathetic activity, 0.04–0.15 Hz), HF power (reflecting primarily parasympathetic activity, 0.15–0.4 Hz), and the LF/HF ratio (as an index of sympathovagal balance) in control and retigabine groups at the 3 time points (n=12). Values represent the mean±SEM. AMI indicates acute myocardial ischemia; HF, high frequency; and LF, low frequency.

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  Figure 4. Effect of retigabine on LSG neural activity and function. A, Representative LSG neural recordings at baseline, post injection, and post AMI in control and retigabine groups. B, C, LSG neuronal firing frequency and discharge amplitude in both groups at the 3 time points (n=12). D, E, Maximal systolic BP change induced by LSG stimulation in both groups at the 3 time points (n=12). Values represent the mean±SEM. ## P<0.01 vs post‐injection. AMI indicates acute myocardial ischemia; BP, blood pressure; HASDA, high‐amplitude spike discharge activity; LSG, left stellate ganglion; and SBP, systolic blood pressure.

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  Figure 5. RTG intervention attenuated the elevation of plasma norepinephrine concentrations post AMI. AMI (15 minute) and AMI (60 minute) refer to 15 and 60 minutes after ligation of the left anterior descending coronary artery, respectively (n=8). Values represent the mean±SEM. AMI indicates acute myocardial ischemia; CS, coronary sinus; JV, jugular vein; and NE, norepinephrine.

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  Figure 6. Effects of retigabine on ventricular epicardial electrical heterogeneity and ventricular stability. A, Representative APD recordings from the left ventricular epicardium in the IA at baseline, 30 minutes post intervention, and post AMI (pacing cycle length: 300 ms) in control and retigabine groups. B, VFT comparison between control and retigabine groups 1 hour post AMI (n=12). C–F, ERP and (G–J) APD90 measurements and dispersion in IA, IBZ, and IRA at 3 time points (n=12). K–M, Longest pacing cycle length inducing APDA in IA, IBZ, and IRA at baseline and post AMI (n=12). N, BVR at 3 time points (n=12). Values represent the mean±SEM. AMI indicates acute myocardial ischemia; APD, action repolarization duration; BVR, beat‐to‐beat variability of repolarization; CV, coefficient of variation; ERP, effective refractory period; IA, ischemic area; IBZ, ischemic area; IRA, ischemia remote area; and VFT, ventricular fibrillation threshold.

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  Figure 7. Effect of retigabine on c‐fos and KCNQ2 expression in LSG neurons. A, Representative immunofluorescence images of KCNQ2 and TH co‐staining in LSG neurons. B, C, Representative immunofluorescence images of c‐fos and TH co‐staining in LSG neurons (left panel) and quantitative analysis (right panel) (n=8 independent ganglia for each group). Values represent the mean±SEM. KCNQ2 indicates potassium voltage‐gated channel subfamily Q member 2; LSG, left stellate ganglion; and TH, tyrosine hydroxylase.

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  Figure 8. Schematic diagram illustrating how retigabine injection into LSG attenuates ischemia‐induced VAs. In the context of an AMI, the phenomenon of sympathetic overactivation gives rise to an increase in neural outflow within the LSG, which in turn results in a disruption to the process of cardiac repolarization. The selective enhancement of M‐channel activity in sympathetic neurons by microinjection of retigabine into the LSG has been demonstrated to increase potassium efflux and hyperpolarize the cell membrane. This modulation has been shown to reduce abnormal neuronal firing, decrease norepinephrine release in both circulating and local cardiac tissue, and attenuate myocardial electrophysiological heterogeneity. Consequently, retigabine has been shown to promote autonomic nervous system homeostasis and reduce the occurrence of spontaneous VAs. ACh indicates acetylcholine; AMI, acute myocardial ischemia; LA, left atrium; LAD, left anterior descending coronary artery; LSG, left stellate ganglion; nAChR, nicotinic acetylcholine receptor; NE, norepinephrine; NPY, neuropeptide Y; PT, pulmonary trunk; and VA, ventricular arrhythmia.