Vet’s 2025 Guide to Aortic (Subaortic) Stenosis in Dogs – Causes, Diagnosis & Care 💓

By Dr. Duncan Houston BVSc

💡 What Is Aortic Stenosis?

Aortic stenosis is a congenital narrowing of the aortic valve or outflow tract in dogs. This forces the left ventricle to generate extra pressure, leading to muscle thickening, reduced cardiac output, and risk of arrhythmias or sudden death.

⚠️ Which Dogs Are at Risk?

• Large breeds: Newfoundlands, Boxers, Rottweilers, Golden Retrievers, Bullmastiffs, Great Danes, German Shepherds, Samoyeds
• Mild cases are often asymptomatic moderate‑to‑severe disease may cause exercise intolerance, fainting, cough, high respiratory effort, or sudden collapse
• Detected as an innocent-sounding murmur early in life, sometimes progressing during growth.

🎯 What You’ll Hear & See

• Crescendo–decrescendo systolic murmur best heard at the left heart base, often radiating toward the neck
• Pulsus parvus et tardus (weak, delayed pulses) in severe cases
• Murmur intensity may increase as the dog matures.

🔬 How Is It Diagnosed?

• Veterinary exam and murmur detection
• Chest X-rays – may reveal left ventricular or aortic enlargement in moderate-to-severe cases
• ECG – left ventricular hypertrophy or arrhythmias may be present in severe disease
• Echocardiography (+ Doppler): gold standard. Shows fibrous ring or ridge, measures blood velocity to estimate pressure gradient, and grades disease as mild (<50 mmHg), moderate (50–80 mmHg), or severe (>80 mmHg)
• Holter monitoring in dogs with syncope or arrhythmias
• Blood and urine tests to assess overall health and suitability for anesthesia/meds.

💊 Treatment & Management

• Mild cases: no medication needed, regular heart check-ups, restrict intense exercise
• Moderate to severe: beta-blockers (e.g., atenolol) to slow heart rate, manage arrhythmias, reduce strain
• Prophylactic antibiotics before invasive procedures due to infective endocarditis risk
• Cutting-balloon valvuloplasty: may temporarily widen outflow tract, but re-stenosis is common, and survival benefits are unclear
• Open-heart surgery bypass techniques are rare and not widely performed due to the high risk.

🏡 Lifestyle & Follow-Up

• Regular echocardiograms every 6–12 months to track progression
• Restrict strenuous exercise to avoid sudden collapse
• Maintain a healthy body condition and weight
• Provide calm mental stimulation and gentle walks
• Consider neutering to prevent breeding affected dogs.

📈 Prognosis

• Mild: dogs live normal lifespans with no treatment
• Moderate–severe: guarded. Severe cases have an increased risk of heart failure or sudden death—~70% survive <3 years even with therapy
• Beta-blockers and monitoring improve longevity and quality of life in many dogs.

🛡️ Breeding & Prevention Tips

• Screen puppies early affected dogs should not be bred
• Use OFA or CHIC heart clearances before breeding
• Raise awareness in breed communities and support genetic counseling.

📲 Tools for Owners & Vets

• Ask A Vet: Telehealth guidance on echo results, medication plans, and emergency signs

🌟 Case Snapshot

Case: “Buddy,” a 6-month-old Newfoundland puppy, was found to have a loud murmur at vaccination. Echo showed moderate SAS (PG ~65 mmHg). He was started on atenolol and had his exercise restricted. At age 5, Buddy remains active, symptom-free, with stable gradients and twice-yearly echo exams. 🐾

✅ Key Takeaways

• Aortic stenosis is a congenital narrowing often found in large-breed puppies.
• Detect via murmur—grade severity with echo and Doppler.
• Mild cases often need minimal intervention severe cases require medical monitoring.
• Beta-blockers, exercise moderation, and echo surveillance improve outcomes.
• Responsible breeding with screening helps reduce disease incidence 🩺

📥 Need Help Now?

If your dog has a heart murmur, fainting signs, or exercise intolerance, download the Ask A Vet app for 24/7 cardiology support. Visit AskAVet.com for expert guidance on diagnostics, medication planning, and lifestyle care. 💓🐾