Shimon Furusato, Kentaro Kurogochi, Masashi Mizuno, Satoru Shinoda, Reo Tanoshima, Masami Uechi

Background
While mitral valve repair surgery significantly improves outcomes for dogs with myxomatous mitral valve disease (MMVD), perioperative mortality remains a concern. Currently, there is no validated model to predict short-term postoperative mortality risk. This study aimed to develop and validate preoperative prediction models for 30-day all-cause mortality following mitral valve repair in dogs with MMVD.

Methods
This retrospective cohort study included 480 client-owned dogs undergoing mitral valve repair for MMVD between 2006 and 2021. Three logistic regression models were developed using preoperative clinical variables to predict 30-day mortality. Variables included age, body weight, echocardiographic measurements, renal function, and the presence of comorbidities. Model performance was assessed using area under the receiver operating characteristic curve (AUROC), calibration plots, and decision curve analysis. The final model was internally validated using bootstrapping.

Results
The overall 30-day mortality rate was 4.4% (21/480). Three models—basic, intermediate, and full—demonstrated AUROCs of 0.73, 0.80, and 0.83, respectively. The full model included eight variables and had the best predictive accuracy. Key predictors included older age, lower body weight, elevated creatinine, higher left atrial-to-aortic ratio, and the presence of pulmonary hypertension. The models were well-calibrated and demonstrated clinical utility in decision curve analysis. A web-based calculator was created for clinical use.

Limitations
Limitations include the retrospective, single-center design and lack of external validation. Changes in surgical techniques over time and missing data for some variables may have affected model consistency. The findings may not generalize to centers with different patient populations or surgical expertise.

Conclusions
The developed preoperative prediction models effectively estimate the risk of 30-day mortality after mitral valve repair in dogs with MMVD. These tools can aid clinical decision-making, inform owners, and guide perioperative planning. External validation is needed before widespread adoption.

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