Diastolic mitral regurgitation in canine heart block
A 12 year-old Springer Spaniel was examined for collapse at exercise and was found to have second degree heart block with a 4:1 p:QRS ratio:
Echocardiography was performed to screen for structural heart disease.
This left apical view shows mitral regurgitation:
But if you look at the ECG trace it’s not happening in association with ventricular systole. This is the spectral Doppler: the phenomenon occurs in the period after each non-conducted atrial contraction.
And the same is occurring on the right side:
left apical view optimised for the tricuspid valve showing diastolic tricuspid regurgitation.
The atrial contraction pushes blood into the already-full ventricle. Normally, ventricular systole contributes to complete mitral valve closure. In its absence the increased ventricular pressure causes regurgitation.
The phenomenon is also recognized in human medicine:
http://circ.ahajournals.org/content/99/21/e13.full
