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

The objectives of this study were to describe pulmonary transit time and myocardial perfusion normalized to heart rate (nPTT and nMP, respectively), evaluated by means of contrast echocardiography, in dogs with stable stage C ACVIM myxomatous mitral valve disease (MMVD), and to assess short-term effects of pimobendan on these parameters. We hypothesized that nPTT and nMP are increased in dogs with MMVD compared to normal dogs. Additionally, we hypothesized that treatment with pimobendan will decrease both variables in dogs with MMVD. We prospectively enrolled 6 normal dogs and 12 dogs with stable stage C ACVIM MMVD. All dogs had a standard and contrast echocardiographic examination at the beginning of the study. 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 means of standard and contrast echocardiography after 1 week (T1), by operators blinded to the dog's treatment. Our results show that nPTT was significantly increased in dogs with MMVD (P = 0.0039), compared to normal dogs. nPTT was significantly decreased at T1 in dogs receiving pimobendan (P = 0.0250). nMP was not significantly different in dogs with MMVD, compared to healthy dogs (P = 0.6639), and it was not significantly different at T1 in the treatment group (P = 0.8798). In conclusion, contrast echocardiography is a valid, complementary tool for echocardiographic analysis of dogs with MMVD. Pimobendan decreases nPTT in dogs affected by MMVD. Myocardial perfusion is not different in dogs with MMVD and is not changed by pimobendan treatment.