Introduction We tested the hypothesis that subcutaneous nerve activity (SCNA) of the thorax correlates with the stellate ganglion nerve activity (SGNA) and can be used to estimate the sympathetic tone. Methods and Results We implanted radiotransmitters in 11 ambulatory dogs to record left SGNA, left thoracic vagal nerve activity (VNA) and left thoracic SCNA, including 3 with simultaneous video monitoring and nerve recording. Two additional dogs were studied under general anesthesia with apamin injected into the right stellate ganglion while the right SGNA and the right SCNA were recorded. There was a significant positive correlation between integrated SGNA (iSGNA) and integrated SCNA (iSCNA) in the first 7 ambulatory dogs, with correlation coefficient of 0.70 (95% confidence interval, CI, 0.61 to 0.84, p < 0.05 for each dog). Tachycardia episodes (heart rate exceeding 150 bpm for ≥3 s), were invariably preceded by SGNA and SCNA. There was circadian variation of both SCNA and SGNA. Crosstalk was ruled out because SGNA, VNA and SCNA bursts had different timing and activation patterns. In an 8th dog, closely spaced bipolar subcutaneous electrodes also recorded SCNA, but with reduced signal to noise ratio. Video monitoring in additional 3 dogs showed that movement was not a cause of high frequency SCNA. The right SGNA correlated strongly with right SCNA and heart rate in 2 anesthetized dogs after apamin injection into the right stellate ganglion. Conclusions SCNA recorded by bipolar subcutaneous electrodes correlates with the SGNA and can be used to estimate the sympathetic tone.

Background Stellate ganglion nerve activity (SGNA) is important in cardiac arrhythmogenesis. However, direct recording of SGNA requires access to the thoracic cavity. Skin of upper thorax is innervated by sympathetic nerve fibers originating from the stellate ganglia (SG) and is easily accessible. Objective To test the hypothesis that thoracic skin nerve activity (SKNA) can be used to estimate SGNA. Methods We recorded SGNA and SKNAs using surface electrocardiogram leads in 5 anesthetized and 4 ambulatory dogs. Apamin injected into the right SG abruptly increased both right SGNA and SKNA in 5 anesthetized dogs. We integrated nerve activities and averaged heart rate in each one-min window over 10 min. We implanted a radiotransmitter to record left SGNA in 4 ambulatory dogs, including two normal dogs, one dog with myocardial infarction and one dog with intermittent rapid atrial pacing. After 2 weeks of recovery, we simultaneously recorded the SKNA and left SGNA continuously for 30 min when the dogs were ambulatory. Results There was a positive correlation (average r=0.877, 95% confidence interval (CI) 0.732 to 1.000, p<0.05 for each dog) between integrated SKNA (iSKNA) and SGNA (iSGNA) and between iSKNA and heart rate (average r=0.837, 95% CI 0.752 to 0.923, p<0.05). Similar to that found in the anesthetized dogs, there was a positive correlation (average r=0.746, 95% CI 0.527 to 0.964, p<0.05) between iSKNA and iSGNA and between iSKNA and heart rate (average r=0.706, 95% CI 0.484 to 0.927, p<0.05). Conclusions SKNAs can be used to estimate SGNA in dogs.

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, T. H. (2019). Ondansetron effects on apaminsensitive small conductance calcium-activated potassium currents in pacing induced failing rabbit hearts. Heart Rhythm.

The use of cardiac magnetic resonance imaging (c-MRI) in risk stratification for clinical outcomes of patients with ischemic cardiomyopathy (ICM) remains low. This systematic review investigated the prognostic value of myocardial fibrosis as assessed by late gadolinium enhancement (LGE) on c-MRI in patients with ICM for ventricular tachyarrhythmia, sudden cardiac death (SCD), or all-cause mortality. Methods We conducted a systematic review of the electronic databases Pubmed and Embase for relevant prospective English-language studies published between January 1990 and February 2019. All included articles were prospective studies that comprised of human participants older than 18 years with ICM and a primary or secondary prevention implantable cardioverter/defibrillator (ICD); had a sample size >30 participants; had at least 6 months of follow-up; and reported on ventricular tachyarrhythmia, SCD, and all-cause mortality. A total of 90 articles related to ICM were identified and were subsequently screened independently by 2 authors. Pooled sensitivity and specificity of LGE were calculated using random-effects model. Results Eight studies with 1,085 participants were included in the final analysis. The mean age of patients varied from 43 to 83 years, with most patients being men. The most common comorbidities reported included history of diabetes mellitus (22%-62%), hyperlipidemia (40%-86%), and hypertension (35%-88%). The ejection fraction of each study was reported as mean or median and varied from 22% to 35%. During a follow-up that ranged from 8.5 to 65 months, there were 110 ventricular arrhythmic events reported. The pooled sensitivity and specificity of LGE for ICD therapy delivered for ventricular arrhythmias were 0.79 (95% CI: 0.66-0.87) and 0.28 (95% CI: 0.14-0.46), respectively. For all-cause mortality, the pooled sensitivity and specificity of LGE were 0.76 (95% CI: 0.40-0.93) and 0.41 (95% CI: 0.14-0.75), respectively. Although SCD was of significant interest to our review, only 1 of the studies reported on the association between LGE and SCD, leading to the subsequent exclusion of SCD from the end point analysis. Conclusions LGE has high prognostic value in predicting adverse outcomes in patients with ICM and may provide helpful information for clinical decision making related to SCD prevention. Our findings illustrate how LGE may improve current risk stratification, prognostication, and selection of patients with ICM for ICD therapy.