Effects of pimobendan on myocardial perfusion and pulmonary transit time in dogs with myxomatous mitral valve disease: a pilot study

Objectives To describe pulmonary transit time (nPTT) and myocardial perfusion (nMP) normalised to heart rate in dogs with stable ACVIM stage C myxomatous mitral valve disease (MMVD) and to assess short‐term effects of pimobendan on these variables. We hypothesised that nPTT and nMP would increase in dogs with MMVD compared with normal dogs. Additionally, we hypothesised that treatment with pimobendan would decrease nMP and nPTT in dogs with MMVD. Design Prospective, single‐blind study involving 6 normal dogs and 12 dogs with MMVD. Methods Dogs with MMVD were treated with enalapril and furosemide for at least 1 month prior to examination. All dogs underwent standard and contrast echocardiographic examinations at the beginning of the study (T0). At this time, MMVD dogs were randomly assigned to receive either pimobendan (0.4–0.6 mg/kg) or not. All dogs with MMVD were re‐evaluated by standard and contrast echocardiography after 1 week (T1) and nPTT and nMP were measured. Results nPTT was significantly increased in dogs with MMVD (P = 0.0063), compared with normal dogs. It was significantly decreased at T1 in dogs receiving pimobendan (P = 0.0250). The nMP was not significantly different in dogs with MMVD, compared with healthy dogs (P = 0.2552), and it was not significantly different at T1 in the treatment group (P = 0.8798). Conclusions Contrast echocardiography was a valid, complementary tool for echocardiographic analysis of dogs with MMVD. Pimobendan decreased nPTT in dogs affected by MMVD. Myocardial perfusion was not different in dogs with severe MMVD.