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

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.