CONDITION

Aortic Stenosis

Why this matters now

Aortic stenosis is present from birth, though it may not be detected immediately as the heart and surrounding structures continue developing during early life. The condition is inherited in several breeds, including Newfoundlands, Golden Retrievers, Rottweilers, and Boxers. Murmurs may become more apparent as puppies grow, and the fibrous narrowing can progress during the first year of life.

The severity of aortic stenosis varies considerably between individuals. Mild cases may cause minimal clinical effects and remain stable. Moderate to severe stenosis places increasing strain on the heart muscle, which thickens in response to the extra workload. Over time, this can lead to reduced exercise tolerance, abnormal heart rhythms, and in severe cases, sudden collapse or heart failure. The condition may progress during the growth period but typically stabilises thereafter.

Signals & patterns

Early signals

Heart murmur detected on examination

A characteristic murmur heard at the left heart base, often detected during routine puppy examinations.

Subtle exercise intolerance

Affected puppies may lag behind littermates during play or tire more easily than expected.

Weaker femoral pulses

The pulse felt in the groin may be less strong than expected, reflecting reduced blood flow through the narrowed valve.

Slightly prolonged recovery after activity

Taking longer to return to normal breathing patterns after exercise.

Later signals

Obvious exercise intolerance

Clear reluctance or inability to exercise at expected levels, with rapid fatigue.

Episodes of weakness or collapse

Transient weakness or fainting, particularly during or after exertion, due to abnormal heart rhythms or inadequate cardiac output.

Laboured breathing

Increased respiratory rate or effort, potentially indicating heart failure development.

Sudden death

Severe cases may unfortunately present with sudden death due to malignant heart rhythm disturbances, often during exercise.

Click to read about the biological mechanisms

How this is usually investigated

Diagnosis involves cardiac auscultation followed by imaging to assess the severity of narrowing and its effects on the heart. Comprehensive evaluation helps determine prognosis.

Cardiac auscultation

Purpose: To detect and characterise the heart murmur
Considerations: Murmur intensity can suggest severity but is not always reliable. Location and radiation of the murmur provide diagnostic clues.

Echocardiography (cardiac ultrasound)

Purpose: To visualise the stenosis, measure its severity, and assess heart structure and function
Considerations: The primary diagnostic tool. Measures blood velocity through the narrowing (pressure gradient) which correlates with severity. Also assesses ventricular wall thickness and function.

Electrocardiogram (ECG)

Purpose: To assess heart rhythm and detect arrhythmias
Considerations: May show changes consistent with left ventricular enlargement. Important for identifying rhythm disturbances that increase risk.

Holter monitoring

Purpose: To record heart rhythm continuously over 24-48 hours
Considerations: Can detect intermittent arrhythmias not apparent on standard ECG. Particularly useful in moderate to severe cases.

Chest radiographs

Purpose: To assess overall heart size and check for signs of heart failure
Considerations: May show left-sided heart enlargement in advanced cases or pulmonary changes if heart failure develops.

Options & trade-offs

Management depends on severity and ranges from monitoring to intervention. Treatment aims to reduce cardiac workload and manage complications.

Monitoring without treatment

Regular cardiac assessments to track progression in mild cases.

Trade-offs: Appropriate for dogs with minimal stenosis. Many mild cases live normal lifespans. Requires commitment to periodic reassessment.

Exercise restriction

Limiting strenuous activity to reduce cardiac demands and arrhythmia risk.

Trade-offs: May help reduce risk of collapse or sudden death. Degree of restriction depends on severity. Can affect quality of life.

Beta-blocker medication

Medications that slow heart rate and reduce cardiac workload.

Trade-offs: May help manage symptoms and potentially reduce arrhythmia risk. Does not address the underlying obstruction. Regular monitoring needed.

Anti-arrhythmic medications

Drugs to control abnormal heart rhythms when these are documented.

Trade-offs: May reduce risk of arrhythmia-related collapse. Selection depends on arrhythmia type. Not always effective.

Interventional procedures (balloon dilation or surgery)

Procedures to reduce the obstruction, though rarely performed.

Trade-offs: May be considered in severe cases. Requires specialised facilities. Results can be temporary as stenosis may recur. Carries procedural risks.

Common misconceptions

Misconception:

"A loud murmur always means severe disease"

Reality:

Whilst murmur intensity can relate to severity, the relationship is not absolute. Echocardiography provides accurate assessment of stenosis severity.

Misconception:

"Dogs with heart murmurs should not exercise at all"

Reality:

Exercise recommendations depend on severity. Dogs with mild stenosis may live normal active lives, whilst those with more significant disease may need restrictions.

Misconception:

"The condition can be completely cured with surgery"

Reality:

Interventional procedures can reduce obstruction but are rarely curative. The fibrous tissue may reform, and underlying heart changes persist. Medical management remains important.

Noting the breed and any known family history of heart conditions provides relevant background. Observing exercise tolerance compared to other dogs of similar age and breed can help identify subtle changes. Documenting any episodes of weakness, excessive fatigue, or collapse, including what activity preceded them, offers valuable information for cardiac evaluation.

Last reviewed: 24 April 2026 · Dr Alastair Greenway MRCVS