Background Exercise testing in conjunction with measurement of cardiac biomarkers NT-proBNP and cTnI is a useful tool for monitoring the effect of treatment on cardiac patients. Administering Pimobendan in dogs with degenerative mitral valve disease (DMVD) and cardiomegaly results in delaying the onset of clinical symptoms and prolonging life. Its effect in dogs with DMVD without cardiomegaly has not been well examined. The aim of the current study was to investigate the effect of administering Pimobendan in dogs with DMVD without cardiomegaly using exercise testing in conjunction with measuring cardiac biomarkers in addition to echocardiography. Twenty-one dogs with asymptomatic DMVD without echocardiographic signs of cardiomegaly participated in a randomised, double-blinded trial. Dogs were divided into a Pimobendan-group ( n = 11) and a placebo-group ( n = 10) in a double-blinded study design and underwent a standardised submaximal exercise test (SSET). One dog in the Pimobendan-group was retrospectively removed from the study after being diagnosed with Leishmaniosis. Cardiac biomarkers NT-proBNP and cTnI were measured before and after exercise. Follow-up appointments were performed at days 90 and 180. Results Dogs in the Pimobendan-group had significantly lower post-exercise NT-proBNP-levels after being administered Pimobendan than at the beginning of the study. They also had lower pre- and post-exercise-NT-proBNP-levels than those dogs in the placebo-group. There was neither a significant difference regarding the measured cTnI levels nor an increase in cTnI between the groups at any time. Conclusions Pimobendan lowers NT-proBNP in dogs with presymptomatic mitral valve disease without cardiomegaly before and after submaximal exercise. This indicates a reduction in cardiac wall stress. If dogs with asymptomatic DMVD without cardiomegaly benefit from treatment with Pimobendan (for example, through a longer survival time) warrants further investigation.

Pimobendan has gained enormous importance in the treatment of mitral valve disease in dogs. The current consensus statement of the American College of Veterinary Internal Medicine (ACVIM) recommends a treatment for dogs with symptomatic disease and dogs with asymptomatic disease with radiographic and echocardiographic signs of cardiomegaly. To investigate whether these dogs also benefit from a therapy with pimobendan, 21 dogs with mitral valve disease ACVIM B1 underwent a standardized submaximal exercise test on a treadmill. In this double-blinded and randomized study, the animals were divided into two groups, one receiving pimobendan and the other a placebo. At the first visit and at every follow-up appointment (at days 90 and 180), heart rate during the complete exercise test and lactate before and after running were measured. In addition to this, a questionnaire was completed by the dogs’ owners and all dogs were given an echocardiographic examination to detect any changes and to observe if the disease had progressed. Due to the diagnosis of leishmaniosis, one dog in the pimobendan group was retrospectively removed from the study so that 20 dogs were included for statistical analysis. No differences were observed at any time between the pimobendan-group and the placebo-group regarding heart rate. At day 180, the increase in lactate after exercise was significantly lower than in the placebo-group. The increase in the pimobendan-group at day 180 was lower than at day 90. Most of the dog owners from the pimobendan-group declared that their dogs were more active at day 90 (6/10) and at day 180 (8/10), while most dog owners from the placebo-group observed no changes regarding activity at day 90 (8/10) and day 180 (6/10). It can be concluded that the results of this study indicate that some dogs with mitral valve disease ACVIM B1 might benefit from a therapy with pimobendan.

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