Heart Disease & Congestive Heart Failure
Includes degenerative valve disease, dilated cardiomyopathy, and congestive heart failure.
What is Heart Disease & Congestive Heart Failure?
The two most common forms in dogs are myxomatous mitral valve disease (MMVD) — a slow degeneration of the mitral valve seen mostly in small breeds — and dilated cardiomyopathy (DCM), where the heart muscle weakens and enlarges, seen mostly in large breeds. Both can eventually lead to congestive heart failure (CHF), when the heart can no longer keep fluid out of the lungs or abdomen.
Common signs and symptoms
Signs vary between dogs and can be subtle at first. Watch for the following, especially if several appear together or persist for more than a few days:
- Persistent cough, especially at night or when lying down
- Faster breathing at rest (>30 breaths per minute while sleeping)
- Reduced stamina, tiring on familiar walks
- Fainting or collapse episodes
- Abdominal swelling
- Restlessness or unwillingness to lie flat
Risk factors
Certain dogs are more predisposed. Understanding risk helps you screen earlier and act sooner.
- MMVD: Cavalier King Charles Spaniel, Dachshund, Chihuahua, small breeds 8+
- DCM: Dobermann, Boxer, Great Dane, Irish Wolfhound, Cocker Spaniel
- Diet-associated DCM linked to some grain-free formulations
- Untreated heartworm or chronic tachyarrhythmias
When to see a vet
Use this as general triage guidance, not a substitute for veterinary advice.
- Book a routine appointment if: you hear a new cough, notice reduced exercise tolerance, or your vet has ever mentioned a heart murmur.
- Seek urgent care if: blue or grey gums, open-mouth breathing at rest, collapse, or a sudden increase in resting breathing rate above 40.
Diagnosis and management
Diagnosis uses stethoscope exam, chest X-rays, echocardiogram, ECG, and blood biomarkers (NT-proBNP). Once heart disease is confirmed, tracking sleeping respiratory rate at home is one of the most useful monitoring tools. Medications like pimobendan, ACE inhibitors, diuretics, and spironolactone can add quality years. Early diagnosis in preclinical MMVD (stage B2) can meaningfully delay heart failure.