Electrophysiological and antiarrhythmic effects of the atrial selective 5-HT(4) receptor antagonist RS-100302 in experimental atrial flutter and fibrillation.

M M Rahme, B Cotter, E Leistad, M K Wadhwa, R Mohabir, A P Ford, R M Eglen, G K Feld

Cardiac Electrophysiology Program, Division of Cardiology, Department of Medicine, University of California, San Diego, USA.

Circulation 1999 Nov 9

filter terms:

Stimulation of 5-HT(4) receptors increases atrial chronotropic and inotropic responses. Whether other electrophysiological effects are produced is unknown. In humans and swine, 5-HT(4) receptors are present only in atrium. Therefore, the effects of a novel 5-HT(4) receptor antagonist, RS-100302, and the partial agonist cisapride on atrial flutter and fibrillation induced in swine were studied to delineate the role of the 5-HT(4) receptor in modulating atrial electrophysiological properties and the antiarrhythmic potential of RS-100302. In 17 anesthetized, open-chest, juvenile pigs, atrial flutter or fibrillation was induced by rapid right atrial pacing with or without a right atrial free wall crush injury, respectively. Atrial effective refractory period (ERP), conduction velocity, wavelength, and dispersion of refractoriness were determined during programmed stimulation via a 56-electrode mapping plaque sutured to the right atrial free wall. Ventricular electrophysiological parameters were also measured. All electrophysiological parameters were measured at baseline and after infusion of RS-100302 and cisapride. In the atrium, RS-100302 prolonged mean ERP (115+/-8 versus 146+/-7 ms, P<0.01) and wavelength (8.3+/-0.9 versus 9.9+/-0.8 cm, P<0.01), reduced dispersion of ERP (15+/-5 versus 8+/-1 ms, P<0.01), and minimally slowed conduction velocity (72+/-4 versus 67+/-5 cm/s, P<0.01). These effects were all partially reversed by cisapride. RS-100302 produced no ventricular electrophysiological effects. RS-100302 terminated atrial flutter in 6 of 8 animals and atrial fibrillation in 8 of 9 animals and prevented reinduction of sustained tachycardia in all animals. The electrophysiological profile of RS-100302 suggests that it may have atrial antiarrhythmic potential without producing ventricular proarrhythmic effects.

Citation

M M Rahme, B Cotter, E Leistad, M K Wadhwa, R Mohabir, A P Ford, R M Eglen, G K Feld. Electrophysiological and antiarrhythmic effects of the atrial selective 5-HT(4) receptor antagonist RS-100302 in experimental atrial flutter and fibrillation. Circulation. 1999 Nov 9;100(19):2010-7