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Ventricular Rate Control During Atrial Fibrillation by Cardiac Parasympathetic Nerve Stimulation: a Transvenous Approach Patrick Schauerte, MD, Benjamin J

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Ventricular Rate Control During Atrial Fibrillation by Cardiac Parasympathetic Nerve Stimulation: a Transvenous Approach Patrick Schauerte, MD, Benjamin J View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector Journal of the American College of Cardiology Vol. 34, No. 7, 1999 © 1999 by the American College of Cardiology ISSN 0735-1097/99/$20.00 Published by Elsevier Science Inc. PII S0735-1097(99)00471-4 Ventricular Rate Control During Atrial Fibrillation by Cardiac Parasympathetic Nerve Stimulation: A Transvenous Approach Patrick Schauerte, MD, Benjamin J. Scherlag, PHD, FACC, Michael A. Scherlag, MD, Sunil Goli, MD, Warren M. Jackman, MD, FACC, Ralph Lazzara, MD, FACC Oklahoma City, Oklahoma OBJECTIVES To identify intravascular sites for continuous, stable parasympathetic stimulation (PS) in order to control the ventricular rate during atrial fibrillation (AF). BACKGROUND Ventricular rate control during AF in patients with congestive heart failure is a significant clinical problem because many drugs that slow the ventricular rate may depress ventricular function and cause hypotension. Parasympathetic stimulation can exert negative dromotropic effects without significantly affecting the ventricles. METHODS In 22 dogs, PS was performed using rectangular stimuli (0.05 ms duration, 20 Hz) delivered through a catheter with an expandable electrode-basket at its end. The catheter was positioned either in the superior vena cava (SVC, n ϭ 6), coronary sinus (CS, n ϭ 10) or right pulmonary artery (RPA, n ϭ 6). The basket was then expanded to obtain long-term catheter stability. Atrial fibrillation was induced and maintained by rapid atrial pacing. RESULTS Nonfluoroscopic (SVC) and fluoroscopic (CS/RPA) identification of effective intravascular PS sites was achieved within 3 to 10 min. The ventricular rate slowing effect during AF started and ceased immediately after on-offset of PS, respectively, and could be maintained over 20 h. In the SVC, at least a 50% increase of ventricular rate (R-R) intervals occurred at 22 Ϯ 11 V (331 Ϯ 139 ms to 653 Ϯ 286 ms, p Ͻ 0.001), in the CS at 16 Ϯ 10 V (312 Ϯ 102 ms vs. 561 Ϯ 172 ms, p Ͻ 0.001) and in the RPA at 18 Ϯ 7 V (307 Ϯ 62 ms to 681 Ϯ 151 ms, p Ͻ 0.001). Parasympathetic stimulation did not change ventricular refractory periods. CONCLUSIONS Intravascular PS results in a significant ventricular rate slowing during AF in dogs. This may be beneficial in patients with AF and rapid ventricular response since many drugs that decrease atrioventricular conduction have negative inotropic effects which could worsen concomitant congestive heart failure. (J Am Coll Cardiol 1999;34:2043–50) © 1999 by the American College of Cardiology Atrial fibrillation (AF) is the most common cardiac arrhyth- the administration of drugs with an immediate depressant mia with a prevalence of 2.3% in people older than 40 years effect on atrioventricular (AV) conduction. However, drugs and 5.9% in those older than 65 years (1). Among other generally used for that purpose such as beta-receptor antag- cardiac and noncardiac risk factors, congestive heart failure onists and calcium-channel antagonists may also lead to imposes the greatest risk of developing AF with a 4.5-fold worsening of concomitant congestive heart failure and increased risk in men and 5.9-fold increased risk in women hypotension. Amiodarone and digoxin may be used for (2). Moreover, in patients with overt congestive heart acute R-R control especially in patients with concomitant failure, the prevalence of AF can rise up to 40% (3). congestive heart failure; yet, for both drugs there is a latency Ventricular rate (R-R) control during AF in patients with of the onset of the negative dromotropic effect of at least congestive heart failure is a significant clinical problem. The 60 min (4,5). acute treatment of rapid ventricular response to AF requires We hypothesized that intravascular electrical stimulation of parasympathetic cardiac nerves which innervate the AV node might decrease the rapid ventricular response during From the Cardiovascular Section, Department of Internal Medicine, University of AF without affecting ventricular contractility. If so, a Oklahoma Health Sciences Center and Department of Veterans Affairs Medical transvenous approach to obtain stable parasympathetic Center, Oklahoma City, Oklahoma. Dr. Schauerte was supported by a grant from the nerve stimulation might offer a new opportunity for R-R “Friedrich-Wilhelm-Stiftung,” Germany. Manuscript received March 12, 1999; revised manuscript received July 2, 1999, control during AF, especially in patients with depressed accepted September 1, 1999. ventricular function. 2044 Schauerte et al. JACC Vol. 34, No. 7, 1999 Intravascular Nerve Stimulation and Atrial Fibrillation December 1999:2043–50 Abbreviations and Acronyms AF ϭ atrial fibrillation AV ϭ atrioventricular CS ϭ coronary sinus ERP ϭ effective refractory period PS ϭ parasympathetic stimulation RAA ϭ right atrial appendage RPA ϭ right pulmonary artery R-R ϭ ventricular rate SST ϭ stimulus strength SVC ϭ superior vena cava METHODS Surgical preparations. All animal studies were approved by the Research and Development Committee of the Department of Veterans Affairs Medical Center, Oklahoma City, Oklahoma. In 22 adult mongrel dogs (weight 18 to 30 kg), anesthesia was induced and maintained with intra- venous sodium pentobarbital (30 mg/kg initial/50 to 100 mg for maintenance). The dogs were intubated and ventilated with room air (Harvard Apparatus Co., Natick, Massachusetts). A cannula was inserted into the left external jugular vein for fluid and drug delivery. Blood pressure was monitored through a cannula in the right femoral artery. A quadripolar catheter with 2 mm interelectrode spacing was introduced into the left carotid artery and advanced to the aortic root to record His bundle activity. A right lateral thoracotomy was performed at the fourth intercostal space. After pericardiotomy pairs of plunge wire electrodes were inserted into the right atrial appendage (RAA) and right ventricular apex for pacing and local electrogram recording. Electrocardiograms lead II and aVR were monitored con- tinuously. All tracings were amplified and digitally recorded using a computer-based Bard Labsystem (CR Bard Inc., Billerica, Massachusetts). Electrocardiogram filter settings were 0.01 to 250 Hz, whereas bipolar electrograms were filtered at 30 to 250 Hz. Parasympathetic stimulation (PS). A 7-French basket catheter (Cordis Webster Corp., Diamond Bar, California) was used for PS (Fig. 1 and 2). Bipolar stimulation and Figure 1. electrogram recording could be performed over adjacent pairs Radiogram (90° right lateral view) showing the basket catheter at a successful cardiac nerve stimulation site in the RPA. of five metal electrode arms. Periods of electrical stimulation Panel A illustrates the catheter arrangement before the injection of lasting 10 s were delivered by a Grass stimulator (Astro- 20 ml of nonionic contrast medium in the right ventricle whereas Med, Inc., Grass Instruments Division, West Warwick, panel B depicts the same site after injection of contrast medium. Rhode Island) at a frequency of 20 Hz and a pulse duration The intravascular stimulation site was located in the proximal of 0.05 ms. These parameters had been demonstrated to be RPA. In this dog, a basket catheter was also introduced into the CS. Panel C gives a schematic explanation. CS ϭ coronary sinus; suitable for epicardial PS while being subthreshold for Hb ϭ His bundle; LV ϭ left ventricle; PA ϭ pulmonary artery; excitation of myocardium (6). The stimulation voltage, RPA ϭ right pulmonary artery. which was delivered through a pair of splines of the basket catheter, was monitored on an oscilloscope (Tektronix 335, Tokyo, Japan). Parasympathetic stimulation at each of three performed during AF. The latter was induced and main- intravascular stimulation sites [superior vena cava (SVC), tained by constant rapid pacing at a cycle length of 100 ms coronary sinus (CS) and right pulmonary artery (RPA)] was from the RAA. Once the effective CS, RPA or SVC site JACC Vol. 34, No. 7, 1999 Schauerte et al. 2045 December 1999:2043–50 Intravascular Nerve Stimulation and Atrial Fibrillation For PS in the .(10 ؍ Group 1: stimulation at the CS (n CS, the catheter was introduced through the right or left external jugular vein and advanced into the right atrium. Positioning in the os of the CS was then performed under fluoroscopic guidance. When the CS had been entered, the basket was expanded to hold the catheter in a stable position against the endovascular surface. Stimulation over each adjacent pair of electrode arms was then attempted at a catheter output voltage of 16 V. If no visible slowing of the ventricular rate during AF was observed, the basket was contracted and the catheter gently rotated or advanced further into the CS until an effective stimulation site was found. In three dogs, additional epicardial stimulation of parasympathetic ganglia was performed using a handheld bipolar stimulation electrode (electrode spacing: 5 mm). This electrode was positioned on the fat pad at the junction of the inferior cava and the left atrium. For placement .(6 ؍ Group 2: stimulation in the RPA (n of the catheter in the RPA, the basket catheter was introduced through a purse-string suture in the right ven- tricular outflow tract. Under fluoroscopic control it was then advanced into the proximal RPA. The sinus rate slowing was assessed by stimulation over each adjacent pair of electrode arms at a catheter output voltage of 27 V. If no visible ventricular rate slowing during AF occurred, the basket was contracted and withdrawn stepwise. Stimulation was repeated until a noticeable drop in ventricular rate during AF was achieved. Figure 1 shows a pulmonary angiogram with the basket catheter positioned at an effective stimulation site. For stimulation .(6 ؍ Group 3: stimulation in the SVC (n in the SVC, the catheter was introduced through the right or left external jugular vein until a right atrial electrogram was recorded in one of the pairs of electrode arms of the basket.
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