Background and aim of the study: Cervical vagal stimulation in rabbits frequently causes bigeminy due to premature ventricular contractions, which is followed by systolic murmur and mitral regurgitation (MR). Peculiar lesions of the mitral valves, mitral annulus and papillary muscles frequently develop within a week. The study aim was to identify the relationship between the direction of MR jet and the site of mitral complex lesions in this experimental model of MR.
Methods: Color Doppler echocardiography was performed on anesthetized rabbits to examine MR, with simultaneous electrocardiographic monitoring. The animals in which the MR jet following cervical vagal stimulation streamed forward or backward alone in the left atrium were dissected on the day of vagal stimulation (n = 11) or one week later (n = 14), and their mitral complex lesions examined.
Results: Among 11 animals dissected on the day of vagal stimulation, six of seven in which the MR jet streamed backward in the left atrium showed marked bleeding only in the anterior mitral leaflet, and three of four in which the MR jet streamed forward showed marked bleeding only in the posterior mitral leaflet. Among 14 animals dissected one week later, eight of 10 in which the MR jet streamed backward showed marked lesions only in the anterior mitral leaflet or anterior papillary muscle, and three of four in which the MR jet streamed forward, showed marked lesions only in the posterior leaflet or posterior papillary muscle.
Conclusion: A close relationship was detected between the direction of MR jet and the site of mitral complex lesion, suggesting that mitral valve prolapse might be, at least in part, the cause of MR.