Quantification of Mitral Valve Regurgitation in Cavalier King Charles Spaniels and Chihuahuas Using Radius of Proximal Isovelocity Surface Area

Simple Summary Our study addresses a significant challenge in veterinary cardiology by improving the measurement of mitral regurgitation severity in dogs with myxomatous mitral valve disease, the most prevalent heart condition in dogs, particularly affecting breeds like Cavalier King Charles Spaniels and Chihuahuas. An accurate assessment of mitral regurgitation severity helps refine treatment decisions and disease monitoring, but the simple and reliable standard method still needs to be improved. This study evaluated 124 client-owned dogs using the proximal isovelocity surface area radius method (PISA-r). Our findings demonstrate that this measurement is accurate and consistent. We established specific threshold values for PISA-r important for determining the disease stage and making informed treatment choices. Notably, this measurement correlates strongly with other heart measurements, such as the left atrium size and left ventricular internal diameter, indicating its comprehensive assessment capability. The proximal isovelocity surface area radius increases significantly with disease progression. Statistical analysis confirms a high accuracy in classifying disease stages, with excellent sensitivity and specificity. Moreover, the PISA-r method exhibits excellent repeatability and reproducibility. Our research suggests that the PISA-r method is a valuable tool for diagnosing and managing dogs with myxomatous mitral valve disease.Abstract Mitral regurgitation (MR) resulting from myxomatous mitral valve disease (MMVD) is a prevalent condition in dogs, particularly smaller breeds like Cavalier King Charles Spaniels (CKCSs) and Chihuahuas (CHHs). An accurate assessment of MR severity is essential for effective treatment and disease monitoring, yet a standardized method has yet to be established. In this retrospective study, we evaluated 124 client-owned dogs diagnosed with MMVD, including 64 CKCSs and 60 CHHs. Dogs were categorized into three stages: asymptomatic (B1), remodeled (B2), and congestive heart failure (CHF, C). The MR severity was quantified using the proximal isovelocity surface area (PISA) method, specifically focusing on the PISA radius (PISA-r). The PISA-r measurements exhibited significant increases across disease stages and demonstrated strong correlations with echocardiographic parameters (ranging from 0.83 to 0.94), including the left atrial size and left ventricular internal diameter. The receiver operating characteristic (ROC) curve analysis revealed the high sensitivity and specificity of PISA-r in classifying disease stages, establishing optimal cut-off values. The method displayed excellent repeatability (interobserver variability: 0.95) and reproducibility (intraobserver variability: 0.97). In conclusion, the PISA method, specifically PISA-r, was reliable for assessing MR severity in dogs with MMVD. By simplifying the diagnosis and management of MR, this research can potentially improve the life and management of MMVD-affected dogs.