Heart Murmurs in Dogs: 2025 Vet Guide by a Vet 🩺🐶

By Dr. Duncan Houston BVSc

Hello, I’m Dr Duncan Houston, BVSc, veterinarian and founder of Ask A Vet. In this comprehensive 2025 guide, we’ll explore heart murmurs in dogs—what they are, when they matter, diagnostic steps, treatment options, home care, and how telehealth is transforming monitoring.

1. What Is a Heart Murmur?

A heart murmur is an abnormal “whooshing” or “swishing” sound heard with a stethoscope, caused by turbulent blood flow in or near the heart. It’s not a disease but a sign that can originate from valve issues, structural defects, high flow states, or entirely benign causes.

2. 🎼 Innocent vs Pathological Murmurs

• Innocent/physiologic murmurs are common in puppies and often disappear by 4–6 months. They’re soft (grade I–II) and not associated with heart disease.
• Pathological murmurs stem from structural issues like valve degeneration, congenital defects, cardiomyopathy, anemia, or infection in older dogs.
• Functional/extracardiac murmurs are due to anemia, fever, hyperthyroidism, or rapid flow states, transient and benign.

3. 🎧 Grading a Murmur

Murmurs are graded I–VI based on loudness:

• Grade I: Very soft
• II: Soft but heard
• III: Moderate
• IV: Loud
• V: Very loud with thrill
• VI: Audible without a stethoscope

Grade doesn’t always mean severity—an innocent murmur could be loud, but a quiet (grade I) murmur may signal serious disease.

4. 📌 Causes of Heart Murmurs

• Mitral regurgitation—most common in small breeds, due to valve degeneration.
• DCM-related leakage in large breeds like Dobermans, Boxers.
• Congenital defects—PDA, VSD, SAS, pulmonic stenosis; often identified early.
• Endocarditis & heartworm can also cause murmurs.
• Anemia/fever/thyroid issues can create benign murmurs.

5. 👂 Interpreting When You Hear One

Veterinarians evaluate murmurs by:

• Timing: Systolic (between lub-dub) vs diastolic vs continuous
• Location: e.g., mitral area—left apex; aortic—left base
• Quality: Musical, blowing, harsh
• Intensity: softer or louder with excitement/stress

6. 🩺 Diagnostic Pathways (2025)

1. Recheck in calm or puppy murmur scenario—repeat auscultation.
2. Chest X-rays for heart size, pulmonary changes
3. ECG to detect arrhythmias in murmurs.
4. Echocardiogram + Doppler—gold standard to assess valve anatomy and leak severity.
5. Bloodwork—CBC, thyroid, NT-proBNP, infectious disease titers
6. Referral to cardiologist for advanced imaging or interventional options

7. 🛠 Treatment Based on Cause

• No action: Innocent murmurs need no treatment; monitor periodically.
• Valve disease: Pimobendan, ACE inhibitors, and diuretics when CHF occurs.
• Congenital anomalies: Surgery (PDA ligation) or balloon valvuloplasty (SAS/pulmonic).
• Systemic causes: Treat anemia, thyroid issues, or fever conditions.
• Arrhythmias: Treated with medications or pacemakers as needed

8. 🏡 Home Care & Monitoring

• Track breathing rate (>35/min at rest is a red flag).
• Watch for coughing, exercise intolerance, pale gums, fainting.
• Maintain a healthy weight; avoid excessive sodium
• Follow-up auscultation every 3–12 months based on risk
• Administer cardiac meds and log with reminders

9. 🌐 2025 Telehealth & Tech Advances

• Wearable stethoscope/ECG patches: to screen murmurs and arrhythmias
• AI sound analysis: detects murmur grade & irregularities early
• Echo/ECG uploads: remote cardiologist review via Ask A Vet
• App notifications: for vital signs, medication schedules, and alerts for cough or tachypnea
• Virtual consults: reduce stress and travel for cardiac cases

10. 🔍 Prognosis by Underlying Cause

• Innocent murmurs: Excellent outcome—resolve by adulthood.
• Valve disease: Variable—early meds extend life; CHF requires lifelong care.
• Congenital defects: Many are surgically correctable, with good long-term prognosis.
• Cardiomyopathy-associated: Guarded prognosis; depends on arrhythmia and CHF severity.

11. 🐕 Breed & Age Considerations

• Puppies/young dogs: Innocent murmurs are common in rapid growth stages.
• Small breeds: Prone to MMVD and mitral murmurs.
• Large breeds: Monitor for DCM-related murmurs even without symptoms.
• Breeding dogs: Echo before breeding to avoid congenital defects.

12. 💬 FAQs From Pet Owners

Does a murmur always mean heart disease?

Not always—many murmurs are benign, especially in young dogs.

Should I worry about a soft murmur?

Soft murmurs warrant monitoring, but severity lies in the cause, not volume.

Can surgery fix a murmur?

Yes—for congenital defects like PDA or SAS—but not for degenerative valve disease.

When is CHF likely?

Cough, lethargy, rapid breathing, fainting—indicate murmur progressing to heart failure.

13. ❤️ Ask A Vet Telehealth Integration

• Upload stethoscope recordings & ECG/Doppler echo for remote review
• Receive AI alerts on murmurs or irregular rhythms
• Schedule virtual consults for interpretation and next-step guidance
• Track medications, diagnostics, and signs using the app
• Coordinate seamlessly with your local vet team for in-person care

Download Ask A Vet to support your dog’s heart health from anywhere. 🐾❤️

14. 🔚 Final Thoughts

Heart murmurs in dogs can be innocent or serious. While many murmurs, especially in young pups, are harmless, others signal underlying conditions—valve disease, congenital defects, or cardiomyopathy. Accurate evaluation through auscultation, echocardiography, ECG, and bloodwork allows targeted care. With stage-appropriate treatments, home monitoring, and telehealth, most dogs live full lives with heart murmurs managed effectively. Always consult your vet or a cardiologist if murmurs are detected—your pup’s heart deserves expert attention.

— Dr Duncan Houston, BVSc