Comparison of atrial fibrillation inducibility by electrical stimulation of either the extrinsic or the intrinsic autonomic nervous systems.

Objectives: To study the effects of bilateral vagosympathetic nerve stimulation (VNS) and ganglionated plexi stimulation (GPS) on atrial refractoriness and inducibility of atrial fibrillation (AF).

Methods: Studies were performed in fourteen adult mongrel dogs anesthetized with Na-pentobarbital, 30 mg/kg. VNS was achieved by insertion of wires into the left and right VN trunks.

The effects of caffeine on the inducibility of atrial fibrillation.

Introduction: There is widespread belief that caffeine consumption is linked to atrial arrhythmias; however, there is a relative lack of systematic evidence to support the assertion. The purpose of this study was to investigate whether caffeine, in doses equivalent to daily use in the general population, alter the propensity for atrial fibrillation (AF) in an experimental model comparing normal and simulated predisposition to AF.

Methods And Material: Caffeine (caffeine Na benzoate, 50:50 mixture) was administered intravenously at 1, 3, and 5 mg/kg doses in dogs producing serum levels of 2 to 4, 5 to 7, and 8 to 10 microg/mL.

Experimental model for paroxysmal atrial fibrillation arising at the pulmonary vein-atrial junctions.

Background: The mechanism(s) by which pulmonary veins (PVs) become ectopically active and subsequently initiate and sustain atrial fibrillation (AF) remains poorly understood.

Objectives: The purpose of this study was to produce an acute canine model of paroxysmal AF arising from the PVs.

Methods: In 11 dogs, a thoracotomy was performed and a 26-gauge needle with a polyethylene tube attached was inserted into a fat pad containing autonomic ganglia at the base of the PV.

Electrical stimulation to identify neural elements on the heart: their role in atrial fibrillation.

Experimental Studies: Anesthetized dogs were subjected to a right then left thoracotomy. Two modes of electrical stimulation were used to activate ganglionated plexi (GP) on the epicardium of the atria: (1) Near the base of each pulmonary vein (PV), trains of high frequency stimuli (HFS) were coupled to each atrial paced beat so as to fall within the refractory period to achieve nerve stimulation without atrial excitation; and (2) Continuous HFS was applied via plaque electrodes sutured to epicardial fat pads (containing a GP) near the right superior (RS) and left superior (LS) PVs. The chest was then closed.

Experimental model of inappropriate sinus tachycardia: initiation and ablation.

Objective: The purpose of the present study was to develop an experimental model of inappropriate sinus tachycardia (IST) by injecting a catecholamine into a fat pad containing autonomic ganglia (AG) innervating the sinus node (SN).

Methods: Initial protocols in 3 groups of pentobarbital anesthetized dogs consisted of (1) slowing the heart rate (HR) by electrical stimulation of AG in the fat pad; (2) the effect of intravenous injection of epinephrine (0.1-0.

Effects on rats of low intensity and frequency electromagnetic field stimulation on thoracic spinal neurons receiving noxious cardiac and esophageal inputs.

Objective  Low intensity and low frequency electromagnetic field stimulation (EMFs) provides substantial pain relief in patients with various chronic pains. The aim of this study was to examine the effects of EMFs on the activity of thoracic spinal neurons responding to noxious visceral stimuli. Materials and Methods  Extracellular potentials of single T(3) -T(4) spinal neurons were recorded in pentobarbital anesthetized male rats.

Magnetism and cardiac arrhythmias.

Low-level electromagnetic fields (EMFs) have been used to treat various neurologic disorders. In the present study, we applied micro Gauss (microG) levels of EMFs either to the vagosympathetic nerve trunks, dissected in the neck, or across the chest in anesthetized dogs. Based on theoretical and empiric grounds, we compared EMFs (2.

Variability of AV nodal potentials recorded, in vivo: direct demonstration of dual AV nodal physiology.

Objectives Of Study: We developed a method to record extracellular A-V nodal potentials in the beating dog heart, in vivo.

Methods: In eleven Na-pentobarbital anesthetized, open-chest dogs, an octapolar electrode catheter (2 mm rings, 2 mm spacing) was inserted through a purse-string suture in the coronary sinus (CS) distal to the ostium and positioned electrographically so that the tip electrode recorded a His bundle (Hb) potential.

Results: Stable recordings of A-V nodal potentials (amplitude, 178 +/- 94 microV; duration 78 +/- 26 msec) were consistently made during sinus rhythm from the second and/or third bipolar pairs of electrodes.

Endovascular stimulation of autonomic neural elements in the superior vena cava using a flexible loop catheter.

It has been previously shown that parasympathetic nerve stimulation (PNS) can be achieved via basket electrode catheters (BEC) positioned in the superior vena cava (SVC). Since questions have been raised regarding formation of thrombi between and/or on the splines of the BECs, we investigated the use of a flexible loop "Lasso" catheter (LC) to achieve autonomic nerve stimulation in the SVC without clot formation. In 5 dogs, anesthetized with Na-pentobarbital, standard ECG leads II and aVR, blood pressure and right atrial electrograms were continuously monitored.

High incidence of thrombus formation without impedance rise during radiofrequency ablation using electrode temperature control.

The authors hypothesized that during RF ablation, the electrode to tissue interface temperature may significantly exceed electrode temperature in the presence of cooling blood flow and produce thrombus. In 12 anesthetized dogs, the skin over the thigh muscle was incised and raised to form a cradle that was superfused with heparinized canine blood (ACT > 350 s) at 37 degrees C. A 7 Fr, 4-mm or 8-mm ablation electrode containing a thermocouple was held perpendicular to the thigh muscle at 10-g contact weight.

Endovascular stimulation within the left pulmonary artery to induce slowing of heart rate and paroxysmal atrial fibrillation.

Objective: In recent years there have been many reports dealing with basic models for sustained atrial fibrillation (AF), however few animal models exist for paroxysmal AF which closely simulate that seen clinically.

Methods: In 12 dogs, anesthetized with sodium pentobarbital, a right thoracotomy was performed. We stabilized a basket electrode catheter within the left pulmonary artery (LPA) through a purse string suture in the right ventricle.