Ventricular rate control during atrial fibrillation by cardiac parasympathetic nerve stimulation: A transvenous approach

OBJECTIVES To identify intravascular sites for continuous, stable parasympa thetic stimulation (PS) in order to control the ventricular rate during atr ial fibrillation (AF). BACKGROUND Ventricular rate control during AF in patients with congestive h eart failure is a significant clinical problem because many drugs that slow the ventricular rate may depress ventricular function and cause hypotensio n. Parasympathetic stimulation can exert negative dromotropic effects witho ut significantly affecting the ventricles. METHODS In 22 dogs, PS was performed using rectangular stimuli (0.05 ms dur ation, 20 Hz) delivered through a catheter with an expandable electrode-bas ket at its end. The catheter was positioned either in the superior vena cav a (SVC, n = 6), coronary sinus (CS, n = 10) or right pulmonary artery (RPA, n = 6). The basket was then expanded to obtain long-term catheter stabilit y. Atrial fibrillation was induced and maintained by rapid atrial pacing. RESULTS Nonfluoroscopic (SVC) and fluoroscopic (CS/RPA) identification of e ffective intravascular PS sites was achieved within 3 to 10 min. The ventri cular 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 +/- 11 V (331 +/- 139 ms to 653 +/- 286 ms, p < 0.001), in the CS at 16 +/ - 10 V (312 +/- 102 ms vs. 561 +/- 172 ms, p < 0.001) and in the RPA at 18 +/- 7 V (307 +/- 62 ms to 681 +/- 151 ms, p < 0.001). Parasympathetic stimu lation did not change ventricular refractory periods. CONCLUSIONS Intravascular PS results in a significant ventricular rate slow ing during AF in dogs. This may be beneficial in patients with AF and rapid ventricular response since many drugs that decrease atrioventricular condu ction have negative inotropic effects which could worsen concomitant conges tive heart failure. (C) 1999 by the American College of Cardiology.