Mitral complex lesions following vagal stimulation in rabbits: relationship between the direction of mitral regurgitation jet and the site of mitral complex lesions.
OBJECTIVE
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.


CONCLUSIONS
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.
Ashida
Terunao
T
Division of Cardiovascular Diseases, The Institute for Adult Diseases Asahi Life Foundation, Tokyo 160-0023, Japan.
Okuno
Shigeru
S
Ebihara
Aya
A
Sugiyama
Takao
T
Fujii
Jun
J
D000818:Animals; D004195:Disease Models, Animal; D018618:Echocardiography, Doppler, Color; D004558:Electric Stimulation; D005260:Female; D008943:Mitral Valve / Q000503:physiopathology*; D008944:Mitral Valve Insufficiency / Q000000981:diagnostic imaging* / Q000209:etiology*; D008945:Mitral Valve Prolapse / Q000000981:diagnostic imaging / Q000209:etiology; D010210:Papillary Muscles / Q000503:physiopathology; D011817:Rabbits; D011897:Random Allocation; D012680:Sensitivity and Specificity; D014630:Vagus Nerve