Effects of subcutaneous nerve stimulation with blindly inserted electrodes on ventricular rate control in a canine model of persistent atrial fibrillation.

Background: Subcutaneous nerve stimulation (ScNS) delivered directly to large subcutaneous nerves can be either antiarrhythmic or proarrhythmic, depending on the stimulus output.

Objective: The purpose of this study was to perform a prospective randomized study in a canine model of persistent AF to test the hypothesis that high-output ScNS using blindly inserted subcutaneous electrodes can reduce ventricular rate (VR) during persistent atrial fibrillation (AF) whereas low-output ScNS would have opposite effects.

Methods: We prospectively randomized 16 male and 15 female dogs with sustained AF (>48 hours) induced by rapid atrial pacing into 3 groups (sham, 0.

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.

Skin sympathetic nerve activity and ventricular rate control during atrial fibrillation.

Background: The relationship between the ventricular rate (VR) during atrial fibrillation (AF) and skin sympathetic nerve activity (SKNA) remains unclear.

Objective: The purpose of this study was to test the hypothesis that SKNA bursts accelerate VR during AF.

Methods: We simultaneously recorded electrocardiogram and SKNA in 8 patients (median age 66.

Effects of anesthetic and sedative agents on sympathetic nerve activity.

Background: The effects of sedative and anesthetic agents on sympathetic nerve activity (SNA) are poorly understood.

Objective: The purpose of this study was to determine the effects of commonly used sedative and anesthetic agents on SNA in ambulatory dogs and humans.

Methods: We implanted radiotransmitters in 6 dogs to record stellate ganglion nerve activity (SGNA), subcutaneous nerve activity (ScNA), and blood pressure (BP).

Subcutaneous nerve stimulation for rate control in ambulatory dogs with persistent atrial fibrillation.

Background: Subcutaneous nerve stimulation (ScNS) damages the stellate ganglion and improves rhythm control of atrial fibrillation (AF) in ambulatory dogs.

Objective: The purpose of this study was to test the hypothesis that thoracic ScNS can improve rate control in persistent AF.

Methods: We created persistent AF in 13 dogs and randomly assigned them to ScNS (n = 6) and sham control (n = 7) groups.

Antiarrhythmic and proarrhythmic effects of subcutaneous nerve stimulation in ambulatory dogs.

Background: High output subcutaneous nerve stimulation (ScNS) remodels the stellate ganglia and suppresses cardiac arrhythmia.

Objective: The purpose of this study was to test the hypothesis that long duration low output ScNS causes cardiac nerve sprouting and increases plasma norepinephrine concentration and the duration of paroxysmal atrial tachycardia (PAT) in ambulatory dogs.

Methods: We prospectively randomized 22 dogs (11 males and 11 females) into 5 different output groups for 2 months of ScNS: 0 mA (sham) (n = 6), 0.

Small-conductance calcium-activated potassium current modulates the ventricular escape rhythm in normal rabbit hearts.

Background: The apamin-sensitive small-conductance calcium-activated K (SK) current I modulates automaticity of the sinus node. I blockade by apamin causes sinus bradycardia.

Objective: The purpose of this study was to test the hypothesis that I modulates ventricular automaticity.

Antiarrhythmic effects of stimulating the left dorsal branch of the thoracic nerve in a canine model of paroxysmal atrial tachyarrhythmias.

Background: Stellate ganglion nerve activity (SGNA) precedes paroxysmal atrial tachyarrhythmia (PAT) episodes in dogs with intermittent rapid left atrial (LA) pacing. The left dorsal branch of the thoracic nerve (LDTN) contains sympathetic nerves originating from the stellate ganglia.

Objective: The purpose of this study was to test the hypothesis that high-frequency electrical stimulation of the LDTN can cause stellate ganglia damage and suppress PATs.

Long-term intermittent high-amplitude subcutaneous nerve stimulation reduces sympathetic tone in ambulatory dogs.

Background: Reducing sympathetic efferent outflow from the stellate ganglia (SG) may be antiarrhythmic.

Objective: The purpose of this study was to test the hypothesis that chronic thoracic subcutaneous nerve stimulation (ScNS) could reduce SG nerve activity (SGNA) and control paroxysmal atrial tachycardia (PAT).

Methods: Thoracic ScNS was performed in 8 dogs while SGNA, vagal nerve activity (VNA), and subcutaneous nerve activity (ScNA) were monitored.

Left cervical vagal nerve stimulation reduces skin sympathetic nerve activity in patients with drug resistant epilepsy.

Background: We recently reported that skin sympathetic nerve activity (SKNA) can be used to estimate sympathetic tone in humans. In animal models, vagal nerve stimulation (VNS) can damage the stellate ganglion, reduce stellate ganglion nerve activity, and suppress cardiac arrhythmia. Whether VNS can suppress sympathetic tone in humans remains unclear.

Simultaneous recordings of intrinsic cardiac nerve activity and skin sympathetic nerve activity from human patients during the postoperative period.

Background: Intrinsic cardiac nerve activity (ICNA) and skin nerve activity (SKNA) are both associated with cardiac arrhythmias in dogs.

Objective: The purpose of this study was to test the hypothesis that ICNA and SKNA correlate with postoperative cardiac arrhythmias in humans.

Methods: Eleven patients (mean age 60 ± 13 years; 4 women) were enrolled in this study.

Skin sympathetic nerve activity precedes the onset and termination of paroxysmal atrial tachycardia and fibrillation.

Background: Skin sympathetic nerve activity (SKNA) is useful for estimating sympathetic tone in humans.

Objective: The purpose of this study was to test the hypotheses that (1) increased SKNA is associated with the onset and termination of paroxysmal atrial tachycardia (AT) and atrial fibrillation (AF) and (2) sinoatrial node response to SKNA is reduced in patients with more frequent AT or AF episodes.

Methods: SKNA and electrocardiogram were recorded in 11 patients (4 men and 7 women; average age 66 ± 10 years), including 3 patients with AT (11 ± 18 episodes per patient) and 8 patients with AF (24 ± 26 episodes per patient).

Simultaneous noninvasive recording of skin sympathetic nerve activity and electrocardiogram.

Background: Sympathetic nerve activity is important to cardiac arrhythmogenesis.

Objective: The purpose of this study was to develop a method for simultaneous noninvasive recording of skin sympathetic nerve activity (SKNA) and electrocardiogram (ECG) using conventional ECG electrodes. This method (neuECG) can be used to adequately estimate sympathetic tone.

Effects of renal sympathetic denervation on the stellate ganglion and brain stem in dogs.

Background: Renal sympathetic denervation (RD) is a promising method of neuromodulation for the management of cardiac arrhythmia.

Objective: We tested the hypothesis that RD is antiarrhythmic in ambulatory dogs because it reduces the stellate ganglion nerve activity (SGNA) by remodeling the stellate ganglion (SG) and brain stem.

Methods: We implanted a radiotransmitter to record SGNA and electrocardiogram in 9 ambulatory dogs for 2 weeks, followed by a second surgery for RD and 2 months SGNA recording.

Arrhythmogenic calmodulin mutations impede activation of small-conductance calcium-activated potassium current.

Background: Apamin-sensitive small-conductance calcium-activated potassium (SK) channels are gated by intracellular Ca(2+) through a constitutive interaction with calmodulin.

Objective: We hypothesize that arrhythmogenic human calmodulin mutations impede activation of SK channels.

Methods: We studied 5 previously published calmodulin mutations (N54I, N98S, D96V, D130G, and F90L).

Small conductance calcium-activated potassium current and the mechanism of atrial arrhythmia in mice with dysfunctional melanocyte-like cells.

Background: The melanin synthesis enzyme dopachrome tautomerase (Dct) regulates intracellular Ca(2+) in melanocytes. Homozygous Dct knockout (Dct(-/-)) adult mice are vulnerable to atrial arrhythmias (AA).

Objective: The purpose of this study was to determine whether apamin-sensitive small conductance Ca(2+)-activated K(+) (SK) currents are upregulated in Dct(-/-) mice and contribute to AA.

Subcutaneous nerve activity and mechanisms of sudden death in a rat model of chronic kidney disease.

Background: The mechanisms of sudden death in chronic kidney disease (CKD) remain unclear.

Objective: The purpose of this study was to test the hypotheses that subcutaneous nerve activity (SCNA) can be used to estimate sympathetic tone in ambulatory rats and that abrupt reduction of SCNA precedes the spontaneous arrhythmic death of Cy/+ rats.

Methods: Radiotransmitters were implanted in ambulatory normal (N = 6) and Cy/+ (CKD; N = 6) rats to record electrocardiogram and SCNA.

Intermittent left cervical vagal nerve stimulation damages the stellate ganglia and reduces the ventricular rate during sustained atrial fibrillation in ambulatory dogs.

Background: The effects of intermittent open-loop vagal nerve stimulation (VNS) on the ventricular rate (VR) during atrial fibrillation (AF) remain unclear.

Objective: The purpose of this study was to test the hypothesis that VNS damages the stellate ganglion (SG) and improves VR control during persistent AF.

Methods: We performed left cervical VNS in ambulatory dogs while recording the left SG nerve activity (SGNA) and vagal nerve activity.

Subcutaneous nerve activity is more accurate than heart rate variability in estimating cardiac sympathetic tone in ambulatory dogs with myocardial infarction.

Background: We recently reported that subcutaneous nerve activity (SCNA) can be used to estimate sympathetic tone.

Objective: The purpose of this study was to test the hypothesis that left thoracic SCNA is more accurate than heart rate variability (HRV) in estimating cardiac sympathetic tone in ambulatory dogs with myocardial infarction (MI).

Methods: We used an implanted radiotransmitter to study left stellate ganglion nerve activity (SGNA), vagal nerve activity (VNA), and thoracic SCNA in 9 dogs at baseline and up to 8 weeks after MI.

SK channels and ventricular arrhythmias in heart failure.

Small-conductance Ca(2+)-activated K(+) (SK) currents are important in the repolarization of normal atrial (but not ventricular) cardiomyocytes. However, recent studies showed that the SK currents are upregulated in failing ventricular cardiomyocytes, along with increased SK channel protein expression and enhanced sensitivity to intracellular Ca(2+). The SK channel activation may be either anti-arrhythmic or pro-arrhythmic, depending on the underlying clinical situations.

Using skin sympathetic nerve activity to estimate stellate ganglion nerve activity in dogs.

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 and is easily accessible.

Subcutaneous nerve activity and spontaneous ventricular arrhythmias in ambulatory dogs.

Background: Stellate ganglion nerve activity (SGNA) is important in ventricular arrhythmogenesis. However, because thoracotomy is needed to access the stellate ganglion, it is difficult to use SGNA for risk stratification.

Objective: The purpose of this study was to test the hypothesis that subcutaneous nerve activity (SCNA) in canines can be used to estimate SGNA and predict ventricular arrhythmia.

Autonomic nerve activity and blood pressure in ambulatory dogs.

Background: The relationship between cardiac autonomic nerve activity and blood pressure (BP) changes in ambulatory dogs is unclear.

Objective: The purpose of this study was to test the hypotheses that simultaneous termination of stellate ganglion nerve activity (SGNA) and vagal nerve activity (VNA) predisposes to spontaneous orthostatic hypotension and that specific β₂-adrenoceptor blockade prevents the hypotensive episodes.

Methods: We used a radiotransmitter to record SGNA, VNA, and BP in eight ambulatory dogs.