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 myo- cardial perfusion (nMP) normalised to heart rate in dogs with sta- ble 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 hypothe- sised 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 examina- tions 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, com- pared 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, comple- mentary tool for echocardiographic analysis of dogs with MMVD. Pimobendan decreased nPTT in dogs affected by MMVD. Myocar- dial perfusion was not different in dogs with severe MMVD. Keywords contrast agents; dogs; echocardiography; myocardial perfusion; myxomatous mitral valve disease; pimobendan; pulmonary transit time Abbreviations Ao, aorta; CHF, congestive heart failure; LA, left atrium; MI, mechanical index; MMVD, myxomatous mitral valve disease; MP, myocardial perfusion; nPTT, normalised pulmonary transit time; nMP, normalised myocardial perfusion; PTT, pulmonary transit time