Objective: To examine our hypothesis that changes of the mitral valve in dogs with mitral regurgitation lead to various degrees of protrusion of the cusp in individual dogs in systole.
Design: Assessing the mitral protrusion, using B-mode echocardiography in dogs with mitral regurgitation.
Animals: 33 dogs with chronic mitral regurgitation and 40 clinically normal dogs.
Procedure: The mitral valve was imaged in the right parasternal left ventricular long-axis view, and we measured the height (H) from the coaptation point or tip of the protruded cusp to the mitral annular plane. When the tip of the protruded cusp was located beyond the mitral annular plane extending into the left atrium, H was expressed as negative values.
Results: The H in clinically normal dogs was 3.7 +/- 0.8 mm. In dogs with mitral regurgitation, the mitral cusp protruded toward the left atrium to various degrees, and H was -0.7 +/- 1.9 mm (range, 2.9 to -5.0 mm). The 2 dogs in the latter group with the lowest H (-5.0 and -4.5 mm, respectively) presented typical mitral flail on B-mode images. The indices of left atrial and ventricular dimension (left atrial dimension/aortic dimension and left ventricular end-diastolic dimension/body weight, respectively) were significantly higher than those in the clinically normal dogs and were negatively correlated with H.
Conclusion: The mitral valve in individual dogs with mitral regurgitation has different degrees of protrusion. The degree of protrusion might be related to the hemo-dynamic condition in mitral regurgitation.