Canine Mitral Valve Disease and Pulmonary Hypertension

Client‐owned dogs that were clinically healthy or had MMVD were prospectively included in our study. Dogs were diagnosed as clinically healthy based on medical history, physical examination, electrocardiography, radiography, noninvasive blood pressure measurement, and transthoracic echocardiography. Dogs were diagnosed as having MMVD based on the presence of mitral valve thickening or prolapse and mitral regurgitation, as identified using transthoracic echocardiography.²⁵ If dogs with MMVD also had tricuspid regurgitation (TR), they were deemed as having PH according to TR ≥3.0 m/s (TR pressure gradient [TRPG] ≥36 mmHg). Dogs that had other cardiac diseases, diseases that might affect the cardiac function or pulmonary artery pressure (eg, respiratory disease, thromboembolic disease, heartworm disease, neoplastic disease, endocrine disease), and systemic hypertension (systolic blood pressure ≥160 mmHg)²⁶ were excluded from the study along with cases that had missing data.
Dogs with MMVD were divided into 3 groups based on the American College of Veterinary Internal Medicine consensus: stage B1 consisted of asymptomatic dogs with no or minimal remodeling, stage B2 consisted of asymptomatic dogs with substantial remodeling based on radiography and echocardiography, and stage C/D consisted of symptomatic dogs with current or past clinical signs of heart failure caused by MMVD.²⁷ In addition, dogs with MMVD were classified into 4 groups based on TRPG: non‐PH, defined as TRPG <36 mmHg or absence of TR; mild PH, defined as TRPG of 36 to 50 mmHg; moderate PH, defined as TRPG of 50 to 75 mmHg; and severe PH, defined as TRPG >75 mmHg.⁵, ¹² Furthermore, dogs with TR were classified qualitatively according to TR severity using color Doppler and continuous wave Doppler methods: mild TR consisted of dogs with a small TR jet based on color Doppler and a faint parabolic TR jet signal based on the continuous wave Doppler; moderate TR consisted of those with an intermediate TR jet and a dense parabolic TR jet signal; and severe TR consisted of those with a substantial large central or eccentric wall‐impinging TR jet and a dense triangular, early‐peaking TR jet signal.²⁸, ²⁹ Dogs were diagnosed as having left‐sided congestive heart failure if they had at least 1 clinical sign, such as tachypnea, respiratory distress, or exercise intolerance, supported by radiographic and ultrasonographic evidence of pulmonary venous congestion and pulmonary edema. Dogs were diagnosed as having R‐CHF if they had at least 1 radiographic and ultrasonographic finding indicative of ascites, pleural effusion or pericardial effusion or clinical signs of cardiac syncope, jugular venous congestion, or peripheral edema without any evidence of diseases except for PH, other than neurological diseases.