Heart disease affects approximately 10% of all dogs, with prevalence increasing significantly with age. Small breeds are predisposed to mitral valve disease (the most common acquired heart disease in dogs), while large breeds are more prone to dilated cardiomyopathy. Early detection through routine auscultation and appropriate staging allows treatment that can extend comfortable life by months to years.
Types of Canine Heart Disease
| Type | Breeds Most Affected | Mechanism |
|---|---|---|
| Mitral Valve Disease (MVD/MMVD) | Cavalier King Charles Spaniel, Dachshund, Chihuahua, Poodle, Yorkshire Terrier | Valve degenerates → blood leaks backward → heart enlarges |
| Dilated Cardiomyopathy (DCM) | Doberman, Great Dane, Boxer, Irish Wolfhound, Cocker Spaniel | Heart muscle weakens → chambers enlarge → pump function declines |
| Pulmonic/Aortic Stenosis | Bulldogs, Boxers, Golden Retrievers (congenital) | Narrowed valve → heart works harder to push blood through |
| Patent Ductus Arteriosus (PDA) | Poodles, German Shepherds, Shelties (congenital) | Fetal blood vessel fails to close → blood shunts abnormally |
Heart Murmur Grading
| Grade | Description | Significance |
|---|---|---|
| I/VI | Very soft, barely audible | May be functional (innocent) or very early disease |
| II/VI | Soft but readily heard | Early valvular disease likely; monitor |
| III/VI | Moderate intensity | Significant disease; echocardiogram recommended |
| IV/VI | Loud | Advanced disease; echocardiogram + treatment likely needed |
| V-VI/VI | Very loud, palpable thrill | Severe disease |
Stages of Heart Disease (ACVIM Classification)
- Stage A: At-risk breed, no disease yet. Monitor.
- Stage B1: Murmur present, no heart enlargement. Monitor every 6-12 months.
- Stage B2: Murmur + heart enlargement on radiograph/echo. Start pimobendan (Vetmedin) — proven to delay onset of heart failure by 15 months.
- Stage C: Heart failure (fluid in lungs or abdomen). Active treatment required.
- Stage D: Refractory heart failure. End-stage management.
Symptoms of Heart Failure
- Cough (especially at night or after rest)
- Rapid/labored breathing
- Exercise intolerance
- Fainting (syncope)
- Distended abdomen (fluid accumulation)
- Restlessness, inability to sleep comfortably
- Blue/gray gums
Treatment
- Pimobendan (Vetmedin): Strengthens heart contraction + dilates blood vessels. First-line for Stage B2 and beyond.
- Furosemide (Lasix): Diuretic — removes fluid from lungs. Essential for heart failure management.
- ACE inhibitors (enalapril, benazepril): Reduce cardiac workload.
- Spironolactone: Mild diuretic + cardiac protective effects.
- Sodium-restricted diet: Reduces fluid retention.
Frequently Asked Questions
My dog has a heart murmur. How serious is it?
Depends entirely on the grade and whether heart enlargement is present. A Grade I-II murmur without enlargement (Stage B1) may require only monitoring for years before treatment is needed. An echocardiogram provides the most accurate assessment of current heart function and helps determine when to start treatment.
Can heart disease be cured?
Most acquired heart disease is managed, not cured. Exception: PDA (congenital) is curable with surgery. Mitral valve repair surgery exists but is limited to specialized centers ($20,000-$40,000). With medical management, many dogs with heart disease live 1-3+ years comfortably after diagnosis.
