Canine cardiology rarely arrives at the clinic labeled as a "cardiology case." It shows up as a murmur discovered by chance during a routine exam, a cough the owner mentions almost in passing, or a senior dog that "tires more easily." The clinician's challenge is to separate the incidental finding from the problem that needs staging and follow-up. This guide organizes that decision in practice.
The murmur on routine auscultation
Finding a murmur is not a diagnosis — it is the start of a line of reasoning. It is worth characterizing it in a structured way:
- Intensity (graded I to VI): louder murmurs tend to correlate with more advanced lesions, but intensity alone does not settle prognosis.
- Point of maximal intensity: left apex suggests the mitral valve; right base, outflow tract or tricuspid lesions.
- Timing in the cycle: systolic, diastolic, or continuous.
- Associated clinical signs: presence or absence of cough, exercise intolerance, resting tachypnea.
In adult small- to medium-breed dogs, a left apical systolic murmur is often compatible with myxomatous mitral valve disease (MMVD). In young dogs, a murmur may indicate congenital heart disease and deserves targeted investigation.
A low-intensity murmur in an asymptomatic dog does not mean urgency — but it does mean the finding must be recorded and reassessed over time, not lost between one visit and the next.
Cough: cardiac or respiratory?
Cough is one of the biggest sources of confusion in practice, because both cardiac and respiratory causes coexist in the same senior patient. Some elements of the history help point the way:
| Clue | More likely suggests |
|---|---|
| Cough with resting tachypnea/dyspnea | Cardiac component / congestion |
| Dry, "goose-honk" cough, worse with excitement or leash pull | Airway (tracheal collapse, bronchitis) |
| Progressive exercise intolerance | Cardiac component |
| Long-standing cough, no progression, alert and stable dog | More likely respiratory |
In practice, the resting respiratory rate (ideally measured at home, during sleep or rest, by the owner) is one of the most useful and inexpensive data points available: persistently elevated values raise suspicion of congestion and justify investigation.
When to investigate heart failure
Congestive heart failure (CHF) is a clinical syndrome, not an isolated imaging finding. It is worth deepening the investigation when warning clinical signs appear:
- Resting tachypnea or dyspnea, or a sustained rise in resting respiratory rate.
- New or progressive exercise intolerance.
- Episodes of syncope or collapse.
- Abdominal distension (ascites) in right-sided heart disease.
- A new murmur, or one that has intensified between visits.
Targeted investigation usually combines:
- Thoracic radiography — assesses the cardiac silhouette and, above all, the presence of pulmonary edema/congestion.
- Echocardiography — characterizes structural lesion, function, and remodeling, and is central to staging.
- Blood pressure and laboratory work as comorbidities require.
- Electrocardiography when arrhythmia or syncope is present.
For MMVD, reasoning through the ACVIM stages (from at-risk/preclinical through clinical and refractory failure) is useful because it connects the finding to management: not every dog with a murmur needs medication, but staging defines who benefits from intervention and how closely to follow up. The practical point is that stage is not static — it evolves, which is why serial documentation matters as much as the initial diagnosis.
The common thread: record and compare over time
The greatest pitfall in routine cardiology is rarely technical — it is the loss of continuity. The grade II murmur described eight months ago, the resting respiratory rate logged at home, the cough that changed in character: these data only have clinical value when they are retrievable and comparable. Scattered across loose notes, each visit starts over from zero.
This is exactly where documenting the consultation well stops being paperwork and becomes a clinical tool. Recording the murmur's characterization, the clinical signs reported by the owner, and the management plan in a structured way lets you, at the next visit, compare and detect progression — which is what drives decisions in chronic heart disease.
Conclusion
In practice, canine cardiology comes down to three linked questions: is this murmur incidental or structural? is this cough cardiac or respiratory? are there clinical signs of congestion that justify investigating heart failure? Answering them well depends less on sophisticated equipment and more on careful auscultation, targeted history, and documented follow-up. The dog with heart disease is, by definition, an evolving patient — and whoever records well today makes better decisions tomorrow.
