Science Digest: How does preclinical pimobendan affect survival times in dogs with myxomatous mitral valve disease, after the onset of congestive heart failure?

15 October 2026

Pimobendan has been shown to prolong survival in dogs with myxomatous mitral valve disease (MMVD) that develop congestive heart failure (CHF), as well as reduce the risk of CHF in dogs with preclinical (stage B2) MMVD that fulfill specific criteria.

However, despite its benefits in delaying disease progression, it’s unclear whether dogs that receive pimobendan before CHF develops have the same survival benefit after CHF onset as those that begin treatment only at that stage.

A new multicentre retrospective study published in the Journal of Veterinary Cardiology compared survival times after the onset of CHF between dogs treated with pimobendan during the preclinical phase of MMVD and those in which treatment with pimobendan was not initiated until the onset of CHF.

The sample population was 137 dogs with the first onset (de novo) CHF secondary to MMVD, from five UK cardiology referral services. The inclusion criteria were small breed (<20 kg body weight), dogs ≥5 years old, with a left apical systolic murmur (≥3/6 intensity) and characteristic echocardiographic changes including mitral valve thickening, prolapse and mitral regurgitation on colour Doppler assessment. The diagnosis of CHF was based on clinical presentation and radiographic and/or lung ultrasound findings and clinical response to diuretic treatment.

At the onset of CHF, 45% of dogs had received pimobendan during the preclinical phase of the disease, while 55% had not previously received pimobendan and were pimobendane-naïve. Following diagnosis of CHF, the median pimobendan dose at discharge was higher than the preclinical dose (0.58 mg/kg/day, compared to the 0.5 mg/kg/day preclinical dose).

Median times to all-cause mortality and cardiac death were shorter in dogs that received pimobendan during the preclinical phase of MMVD than those that did not: 168 days vs. 359 days to all-cause mortality, and 201 days vs. 442 days to cardiac death. There was no difference in the proportions of dogs experiencing cardiac death between groups, with cardiac death occurring in 61% of dogs at a median time of 182 days.

There was no difference in survival times between dogs administered furosemide (median survival time: 301 days) and those administered torasemide (median survival time: 228 days) at discharge, although the study wasn’t adequately powered for meaningful subanalysis of the influence of different drugs.

At the onset of CHF, there were no differences in any echocardiographic measurements between groups, and at discharge, following diagnosis of de novo CHF, treatments were equivalent. This could suggest that dogs given preclinical pimobendan respond less well to administration of equivalent CHF therapy than pimobendan-naïve dogs.

While preclinical pimobendane for MMVD is expected to be the best approach for improving survival and maintaining quality of life, these results suggest that dogs treated with pimobendan before the onset of CHF may have reduced survival times once CHF develops. The authors stress that these results are relevant to dogs with MMVD that develop CHF, rather than all dogs with preclinical MMVD.

These findings should be interpreted with caution due to the limitations inherent in the retrospective study design. Notably, the lack of randomisation between treatment groups may have introduced bias. Additional limitations include uncontrolled variation in patient demographics, diagnostic criteria for CHF, cardiac phenotypes, drug combinations and dosages, and the timing of treatment initiation, along with uneven case recruitment across centres and inconsistent follow-up.

Take home message

The survival times of dogs administered pimobendan during the preclinical phase of MMVD might be shorter following the onset of CHF, compared to those that didn’t receive preclinical pimobendane. Although specific therapeutic recommendations can’t be made from these results, clinicians should remain aware that dogs treated with pimobendan during the preclinical phase may need a different management approach at the onset of CHF compared with pimobendan-naïve dogs.

Reference

McAulay G, Hills M, Dukes-McEwan J, Dutton E, Jakubczak A, Singleton D et al. (2026) Survival of dogs with myxomatous mitral valve disease administered preclinical pimobendan in comparison to pimobendan-naïve dogs from the onset of congestive heart failure. Journal of Veterinary Cardiology. 66, 63-73, https://doi.org/10.1016/j.jvc.2026.05.001.