R-peak time in different clinical stages of canine myxomatous mitral valve disease

Myxomatous mitral valve disease (MMVD) is highly prevalent in dogs. An accurate diagnosis and staging are crucial for effective treatment. While echocardiography is the gold standard for diagnosis, it is operator-dependent and its availability is limited. Conversely, electrocardiography (ECG) is a low-cost widely accessible technology, and variables such as R-peak time (RPT) have been underexplored in MMVD. This study investigated RPT in dogs with MMVD, correlations with disease stages and echocardiographic measures, and its diagnostic performance. Records of 81 dogs were analyzed. RPT differed between stages (A vs. C and D; B1 vs. C and D; B2 vs. C and D), showing a positive correlation with disease stage (ρ=0.830) and cardiac dimensions (LVEDdn - ρ=0.719; LA/Ao - ρ=0.760). The optimal RPT cut-off points and ROC curve AUCs to differentiate dogs with and without MMVD were: 29ms; Youden’s index - 0.739; AUC - 0.892, and to distinguish between the treatment-beneficial group (B2, C, and D) and the healthy/non-beneficial group (A and B1) - 30ms; Youden’s index - 0.850; AUC - 0.935. Although RPT is not suggested as a replacement for echocardiography, the preliminary results indicate its potential use for MMVD screening, especially where echocardiography is unavailable. Prospective studies with lar-ger samples are needed to further investigate these findings and explore additional factors influencing RPT.