The coughing dog with heart disease – important considerations

A 20th-century physician, John Hickam, once stated that “Patients can have as many diseases as they damn well please” – a valuable reminder not to be blindsided by the diagnosis or treatment of a single condition.

A case that illustrates this perfectly is one many in general practice will recognise.

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Chester, a 10-year-old male neutered Shih Tzu, was referred for cardiac investigation following a history of progressive cough and detection of a loud left apical systolic murmur, raising suspicion of congestive heart failure (CHF). He was receiving pimobendan (0.3 mg/kg BID) and had previously shown partial improvement on frusemide (1.7 mg/kg BID), which had since been discontinued.

On clinical examination, Chester’s heart rate was 80 bpm with an irregular rhythm and strong femoral pulses, including palpable pulse deficits. A grade IV left apical systolic murmur was present, but pulmonary auscultation and the remainder of the exam were unremarkable.

Diagnostic findings

• ECG: Predominantly sinus rhythm with intermittent supraventricular premature complexes (SVPCs).
• Blood pressure: 170 mmHg (Doppler, hindlimb).
• Blood tests: Haematology, biochemistry and electrolytes all within normal limits.
• Echocardiography: Mitral and tricuspid regurgitation with degenerative leaflet changes. The left atrium was enlarged (LA:Ao 2.3) and the left ventricle dilated (LVDDN 2.3) with hyperdynamic wall motion but normal estimated filling pressures (MV E vel 1.03 m/s, E/A 1.48). Diagnosis: degenerative mitral valve disease (DMVD), ACVIM stage B2.
• Thoracic radiography: Left-sided cardiomegaly, no evidence of pulmonary oedema, and normal lung fields.
• Bronchoscopy: Normal trachea, carina and right mainstem bronchus, but collapse of the left mainstem bronchus during inspiration.
• BAL: Mild eosinophilic inflammation; culture and PCR negative.

The real culprit

It’s easy to see how CHF could be considered the cause of Chester’s cough – especially given his partial response to diuretics. Unfortunately, this can lead to a common clinical pitfall: progressive, empirically increased diuretic doses in dogs that never truly respond because CHF was never the underlying problem.

In dogs with left atrial enlargement, mechanical irritation of cough receptors at the tracheal bifurcation can add further confusion. In Chester’s case, the murmur and echo findings could easily have explained away the cough, but further investigation told a different story.

Bronchoscopy, with its ability to visualise airway movement in real time, identified left mainstem bronchial collapse as the primary cause. This changed the management approach completely, allowing for targeted therapy, environmental control, and improved owner understanding of the disease process.

Management and outcome

At this stage, Chester did not require diuretics. His management plan focused instead on:

• Medical therapy: Anti-inflammatories, inhaled corticosteroids, and cough suppressants as appropriate.
• Lifestyle measures: Weight management, use of a harness instead of a collar, and minimising exposure to irritants such as cigarette smoke, aerosols, and air fresheners.

By taking diagnostics beyond thoracic radiography, the true cause of Chester’s signs was identified – sparing him unnecessary medication (and its side effects), reducing owner frustration, and ensuring more effective, welfare-focused care.

Let us know if you’d like help with where to go next with your case, or consider referral for relevant investigations, management and treatment plans tailored to the patient needs and client expectations.

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