Long-Term Outcomes of Mitral Valve Repair With Artificial Chordae and Annuloplasty for Myxomatous Mitral Valve Disease in Dogs

Abstract

Background: Myxomatous mitral valve disease (MMVD) in dogs commonly progresses to congestive heart failure, which carries a poor prognosis. Mitral valve repair (MVR) is a recognized treatment for advanced-stage MMVD.

Hypothesis/objectives: Identify the risk factors and prognosis in dogs undergoing MVR.

Animals: We enrolled 1019 dogs with MMVD (ACVIM stages B2, C, and D) that underwent MVR between January 2017 and December 2020.

Methods: Medical records from a single institution were retrospectively reviewed. Early and late postoperative periods were defined as < 100 days and 100-1400 days after surgery, respectively. The outcome was time to a composite of all-cause mortality, onset of postoperative congestive heart failure, or undergoing a second MVR (surgical revision).

Results: In the early postoperative period, 61 dogs experienced the composite outcome; in the late period, 211 dogs did. No dogs underwent a second MVR. The incidence rate was 19.6 and 7.1 events per 1000 dog-months in the early and late periods, respectively. Compared with stage B2 dogs, stage D dogs had 2.2 times the daily hazard of experiencing an early postoperative event. In the late period, increasing age (per year; hazard ratio [HR], 1.3), higher body weight (per kilogram; HR, 1.1), Cavalier King Charles Spaniels compared with Chihuahuas (HR, 2.2), and preoperative tricuspid valve regurgitant velocity > 3.7 m/s (HR, 2.5) were associated with the events.

Conclusions and clinical importance: A higher incidence of the event was observed in the early postoperative period rather than later, with the outcome varying according to MMVD condition and patient-specific factors.

Keywords: cardiopulmonary bypass; chordae replacement; mitral regurgitation; mitral valve insufficiency; mitral valve plasty; open heart surgery.

FIGURE 1

Time‐to‐event curves following mitral valve repair compared among clinical stages. The overall time‐to‐event curve (A) and landmark analysis (B) are presented, divided into two timepoints based on a cutoff limit of 100 days after surgery. This study analyzed data from 1019 client‐owned dogs treated with mitral valve repair at the JASMINE Veterinary Cardiovascular Medical Center in Japan from January 2017 to December 2020. A comparative analysis of time‐to‐event among different clinical stages, as determined by the American College of Veterinary Internal Medicine (ACVIM) consensus guidelines, is shown. Each downward step in the curve represents an endpoint, indicating postoperative events (all‐cause mortality and onset of congestive heart failure; no dogs underwent a second mitral valve repair), and the shaded areas around the curves depict the 95% confidence intervals. Hazard ratios and 95% confidence intervals were extracted from Table 3, and the values for (A) were derived using the same model as the 100–1400 days segment in the landmark analysis.

FIGURE 2

Preoperative and postoperative thoracic radiographic and echocardiographic results. Comparisons across the American College of Veterinary Internal Medicine (ACVIM) clinical stages for several heart‐related metrics are shown. The parameters include vertebral heart score (VHS; A), left atrial to aortic ratio (LA:Ao; B), left ventricular end‐diastolic internal diameter normalized to body weight (LVIDDN; C), and left ventricular systolic internal diameter normalized to body weight (LVIDSN; D). Box plots display the values for each stage, with the median indicated by a central horizontal line within the box. The upper and lower boundaries of the box represent the interquartile range, with the third quartile (75th percentile) at the top and the first quartile (25th percentile) at the bottom. Whiskers extend from the box to the highest and lowest values within 1.5 times the interquartile range from the upper and lower quartiles, respectively. Individual values are presented as points. Additionally, the gray area in the form of a violin plot indicates the distribution of the values for all cases. VHS, vertebral heart score. LA:Ao, left atrial to aortic ratio. LVIDDN, left ventricular end‐diastolic internal diameter normalized to body weight. LVIDSN, left ventricular systolic internal diameter normalized to body weight. ^a p < 0.05 compared with stage B2. ^b p < 0.05 compared with stage C.