Postoperative Automated Platelet Count and Its Predictive Factors in Dogs Undergoing Mitral Valve Repair

ObjectivesThis study aimed to describe early postoperative changes in automated platelet counts (PLT) after mitral valve repair (MVR) in dogs with myxomatous mitral valve disease (MMVD) and to identify factors associated with these changes. DesignSingle-center retrospective cohort study. AnimalsDogs with MMVD that underwent MVR from July 2022 to July 2023. After data extraction, the ten most common breeds were selected, and mixed breeds as well as breeds known for inherent platelet abnormalities (Cavalier King Charles Spaniels and Norfolk Terriers) were excluded. Measurements and Main ResultsA total of 313 dogs representing seven breeds met the inclusion criteria. PLT levels were assessed preoperatively (Day 0) and daily for 4 days postoperatively (Days 1-4). Mean (standard deviation) PLT values were 393{+/-}127 x103/{micro}L on Day 0, 159{+/-}72 on Day 1, 137{+/-}67 on Day 2, 157{+/-}87 on Day 3, and 187{+/-}104 on Day 4. Postoperative thrombocytopenia (<100 x103/{micro}L) occurred in 124 of 313 dogs during Days 1-4. In a multivariable mixed-effects model, PLT declined significantly after surgery (Day 0 to 1; {beta} = -207.17 [x103/{micro}L per day], P < 0.001) and showed a postoperative upward trend (Day 1 to 4; {beta} = 20.62 [x103/{micro}L per day], P = 0.079). Older age was associated with higher PLT; Toy Poodles and Yorkshire Terriers demonstrated lower PLT than Chihuahuas; dogs with ACVIM Stages C- D had higher PLT compared with Stage B2; lower body weight correlated with lower PLT; and intact dogs tended to have higher PLT than neutered dogs. ConclusionsPLT decreased sharply following MVR and demonstrated partial recovery within 5 days. Age, breed, clinical stage, body weight, and neuter status were associated with postoperative PLT patterns, indicating their importance for perioperative assessment and monitoring.