Coughing dogs with mitral valve disease aren’t always in heart failure

December 11, 2025

Severe left atrial enlargement, but not congestive heart failure, increases the probability of coughing in dogs with mitral valve disease. Rishniw, M., Borgarelli, M., Ferasin, L., & Menciotti, G. (2025). Journal of the American Veterinary Medical Association, 1–6. Advance online publication. https://doi.org/10.2460/javma.25.07.0507

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When a patient with known (or suspected) mitral valve disease develops a more frequent or severe cough, it is often assumed that pulmonary oedema has developed – a view still repeated in textbooks, despite limited evidence. While dogs with confirmed congestive heart failure (CHF) can cough, CHF is not typically the primary cause, even when the cough appears to improve with diuretics (which have their own antitussive effects). This paper highlights some very important considerations to your case management. Let’s Dive in…

What did the study look at?

The authors examined dogs diagnosed with myxomatous mitral valve disease (MMVD) to determine whether left atrial enlargement, coughing and the presence of left-sided CHF were associated.

How was the study done?

This was a retrospective analysis pooling data from two earlier studies (2013 and 2020), encompassing 352 small-breed dogs presented to referral practice. Dogs were categorised by degree of left atrial enlargement (calculated using LA:Ao ratio into ‘none’, ‘mild’, ‘moderate’ or ‘severe’), coughing status (‘yes’/ ‘no’) and CHF status (‘present’/ ‘absent’).

What were the outcomes?

Only severe LA enlargement (LA:Ao > 2.29) significantly increased the probability of coughing.
Dogs with mild or moderate LA enlargement had a similar probability of coughing as those with no enlargement.
Presence of CHF was not an independent predictor of cough.
Only 9 of 32 dogs with CHF developed a new cough at the onset of CHF.

Pros and cons of the study

Pros:

Large combined dataset for a veterinary cardiology study, drawn from two well-conducted, well-recognised cohorts.
92% of dogs weighed under 20 kg, limiting heterogeneity and improving relevance to the typical MMVD population.
Use of recognised and repeatable echocardiographic categorisation (LA:Ao) supports applicability in general practice.
Challenges the long-held belief that coughing dogs with MMVD are usually in CHF, shifting focus towards other common causes such as airway disease and prompting more appropriate diagnostic and treatment pathways.

Cons

Retrospective pooling of two studies increases heterogeneity in case selection and clinical thresholds. One dataset was longitudinal, so some dogs contributed multiple time points, introducing within-dog correlation.
Cough was owner-reported without standardisation of frequency, duration or triggers, which limits diagnostic clarity.
Concurrent respiratory disease is a major confounder; however, objective airway investigations (radiography, bronchoscopy, bronchoalveolar lavage) were not consistently available to assess its contribution.
LA:Ao ratio as a lone measurement for left atrial size is unreliable, long axis measurements should also be considered. The paper also does not mention a more holistic approach to echocardiography to include left ventricular dimensions, isovolumetric relaxation time (IVRT), estimated filling pressures or pulmonary venous assessment – all of which are validated means of assessing accurately if congestive heart failure is evident.
Findings predominantly apply to small-breed dogs; the study does not address MMVD populations over 20 kg.

Our thoughts (for the time being…)

Although this study relies on pre-existing datasets, it raises an important point about our habitual reliance on cough as an indicator of CHF. Clinically, we frequently see MMVD patients whose cough is far more attributable to airway disease than to pulmonary oedema. Many are started on diuretics unnecessarily and later considered “unresponsive” or “resistant” to standard CHF therapy, when the true issue is unrecognised respiratory disease. Even those who’s cough improves or resolves with frusemide may simply be experiencing its antitussive effects rather than genuine improvement in CHF, at the expense of renal function.

To more definitively determine whether severe left atrial enlargement is a primary driver of cough in MMVD, a prospective study including standardised respiratory diagnostics would be needed. For now, however, this paper provides a timely reminder to carefully consider all possible causes of cough in these patients – and to avoid relying on cough alone when diagnosing congestive heart failure.

Don’t forget, if you need case advice or your client is motivated for referral, we are here to help!