Clinical Outcomes of Mitral Valve Repair in Dogs With Pulmonary Hypertension Secondary to Myxomatous Mitral Valve Disease

Abstract

Background: Myxomatous mitral valve disease (MMVD) can cause pulmonary hypertension (PH). Mitral valve repair (MVR) has been described as a surgical treatment option for MMVD, but the benefit of MVR when PH is present is unknown.

Hypothesis/objectives: To investigate the change in echocardiographic variables and long-term outcomes of dogs with PH secondary to MMVD after MVR.

Animals: Twenty-one dogs with PH secondary to MMVD that underwent MVR.

Methods: Inclusion criteria were MMVD dogs that had a high probability of PH according to the metrics established in the American College of Veterinary Internal Medicine (ACVIM) consensus statement on PH in dogs, and that had two follow-up evaluations. Echocardiographic variables before MVR were compared with the follow-up evaluations after surgery.

Results: Before surgery, 12 dogs were Stage C whereas 9 dogs were Stage D. Echocardiographically normalized left ventricular internal diameter in diastole (LVIDDN), mitral E wave velocity, the ratio of the left atrial dimension to the aortic annulus dimension (LA/Ao) and tricuspid regurgitation velocity were significantly decreased after surgery (p < 0.01). Complete resolution of preoperative clinical signs was achieved in 71.4% of dogs after surgery. However, two dogs had residual PH (9.5%) and three dogs that had resolution of PH post-operatively had recurrent PH (14.2%).

Conclusions and clinical importance: We showed that most dogs with PH before MVR had decreases in estimated pulmonary arterial pressure after surgery as well as resolution of clinical signs. Some dogs had residual PH and late PH recurrence after MVR, which could suggest underlying pulmonary arterial pathology.

Keywords: canine; cardiac surgery; echocardiography; left‐sided heart disease; prognosis.

FIGURE 1

Changes in echocardiographic images in the case 4 dog with recurrent PH before and after mitral valve repair. Two‐dimensional echocardiography images of the right parasternal long axis 4‐chambers view (B‐mode and color Doppler), right parasternal short axis view at the level of the papillary muscles, and left parasternal apical four‐chamber view for measurement of TR velocity max. The solid line shows the alignment TR was measured. (A) Images pre‐MVR. Enlargement of left and right heart was recognized with severe MR and TR (TR velocity max 3.7 m/s). (B) Images at 3 months post‐MVR. The left‐sided heart lumen size and mitral regurgitation flow decreased after surgery. TR velocity max also was decreased (TR velocity max 2.9 m/s). (C) Images at 12 months post‐MVR. Although right heart size was gradually increased, other echocardiographic signs of PH, such as increased TR velocity max and marked flattening of the interventricular septum, were not recognized. (D) Images at 24 months post‐MVR. The dog was diagnosed with PH based on severe eccentric hypertrophy of the right ventricle, underfilling of the left ventricle, right atrial enlargement, flattening of the interventricular septum, and severe TR at increased velocities (TR velocity max 3.45 m/s). Abbreviations: MR, mitral valve regurgitation; MVR, mitral valve repair; PH, Pulmonary hypertension; TR, tricuspid valve regurgitation.

FIGURE 2

Kaplan–Meier survival curve for 22 dogs with MMVD and PH after MVR. The 50% probabilities of survival are indicated by dotted lines. The median survival time was 767 days (95% CI, 521–851 days). Censored animals are indicated with vertical bars. Abbreviations: MMVD, Myxomatous mitral valve disease; MVR, mitral valve repair; PH, Pulmonary hypertension.