Transvenous parasympathetic cardiac nerve stimulation: An approach for stable sinus rate control

Introduction: Epicardial electrical stimulation of parasympathetic nerves i nnervating the sinus node has been shown to decrease sinus rate. We investi gated whether intravascular parasympathetic cardiac nerve stimulation (IPS) can be achieved over a relatively long-term period to slow the supraventri cular rate. Methods and Results: Fifteen dogs were investigated. IFS was performed with rectangular stimuli (0.05-msec duration, 20 Hz) using a catheter with an e xpandable electrode basket. The catheter was positioned in the superior ven a cava (SVC; n = 9) or right pulmonary artery (RPA; n = 6), The basket then was expanded to hold the catheter in place. Nonfluoroscopic identification of effective IFS sites was achieved within 5 minutes in the SVC, Increasin g IFS voltage resulted in a graded response of supraventricular rate slowin g. A 50% prolongation of the baseline atrial cycle length was achieved with 28 V in the SVC (1,056 +/- 355 msec vs 489 +/- 154 msec; P < 0.001) and 25 V in the RPA (1,181 +/- 306 msec vs 518 +/- 138 msec; P < 0.01), The rate slowing started immediately after IFS onset, terminated abruptly after IFS cessation, and could be maintained over 10 hours. A rate slowing effect als o was observed when the sinus rate was increased by isoproterenol (SVC: 304 +/- 8 msec/RPA: 341 +/- 9 msec with isoproterenol vs SVC: 635 +/- 12 msec with isoproterenol + LPS at 39 V/ RPA: 584 +/- 16 msec with isoproterenol TPS at 38 V; n = 6). Conclusion: IFS results in a significant supraventricular rate slowing that is stable over a relatively long period and may be applied to slow undesir able sinus tachycardia in acute ischemic syndromes or to counteract undesir able chronotropic effects of catecholamines during treatment of cardiogenic or septic shock and acute congestive heart failure.