Aortic stenosis:
when intervention is needed

Article written and reviewed by Dr Luca Moretti

In severe aortic stenosis, the decision to replace the valve does not depend on a single number. If the stenosis is truly severe and causes symptoms such as shortness of breath, chest pain, reduced exercise capacity or fainting, intervention is generally recommended in patients who can benefit from it.
An important change is that it is not always necessary to wait for symptoms. Based on new randomized studies, the 2025 ESC/EACTS guidelines allow earlier treatment to be considered in selected patients with apparently asymptomatic severe stenosis and low procedural risk.

This guide focuses on the timing of intervention. For causes, mechanisms, complete classification and differential diagnosis, see the monograph on aortic stenosis.

Before deciding, it is essential to be sure that the stenosis is severe

The classic form of severe high-gradient aortic stenosis has a set of concordant findings: maximum velocity across the valve of at least 4.0 m/s, mean gradient of at least 40 mmHg and valve area generally no greater than 1.0 cm². These parameters are interpreted together, not as three independent tests.
If valve area, velocity and gradient do not agree, the cardiologist must check measurement quality, blood pressure, the amount of blood ejected by the ventricle and ventricular function. In some cases, stress echocardiography or computed tomography with quantification of valve calcium is needed.

This step is fundamental because an invasive decision should not be based on an uncertain classification. Low-flow, low-gradient aortic stenosis is one of the settings in which integration of the data is particularly important.

When symptoms make intervention necessary

Symptomatic severe aortic stenosis has an unfavorable prognosis if left untreated. In eligible patients, the presence of symptoms attributable to the stenosis is therefore one of the strongest indications for valve replacement.
Symptoms that require particular attention are shortness of breath or reduced exercise capacity, chest pain or pressure, dizziness, presyncope or syncope. A gradual slowing of daily activities can also be a masked symptom: some people do not report “I feel unwell,” but gradually stop doing things they used to do.

When it is unclear whether a person is truly asymptomatic, an exercise test can be useful when clinically appropriate. The development of symptoms during exercise or an abnormal blood-pressure response may change the strategy and lead the patient to be considered no longer truly asymptomatic.

Severe stenosis without symptoms: when simply waiting may not be appropriate

In the past, active surveillance was the usual strategy for many people with severe stenosis and preserved ventricular function who reported no symptoms. More recent evidence has shifted this approach toward a more individualized assessment.
Intervention is recommended if the stenosis is severe and the left ventricular ejection fraction is below 50% without another cause explaining the reduction. The 2025 guidelines also state that, in patients at low procedural risk, early intervention may be considered even when ejection fraction is preserved.

Some findings strengthen the case for early treatment: very severe stenosis, rapid progression, marked valve calcification, markedly elevated BNP or NT-proBNP values without another explanation, and an ejection fraction below 55% while still remaining above the traditional 50% threshold. A sustained fall in blood pressure during exercise testing is also a relevant finding.
These factors should not be used as a do-it-yourself checklist. They help explain why two people who are both “without symptoms” and have severe stenosis may receive different recommendations.

What happens in low-flow cases or when parameters are discordant

In severe low-flow, low-gradient aortic stenosis, the ventricle ejects a reduced amount of blood and the gradient may therefore fail to reach the values typical of high-gradient stenosis. If the ejection fraction is reduced, dobutamine stress echocardiography can help distinguish truly severe stenosis from a valve that appears more narrowed because flow is very low.
Computed tomography with an aortic valve calcium score can provide complementary information. The 2025 European guidelines indicate that values above approximately 2000 Agatston units in men and 1200 in women are strongly suggestive of severe stenosis, always to be interpreted in the clinical context.

If severe stenosis is confirmed and the patient is symptomatic, intervention is generally recommended or considered depending on the type of hemodynamic pattern. If, on the other hand, the assessment suggests pseudo-severe or moderate stenosis, the strategy changes and treatment is directed toward other causes of low flow and follow-up.

TAVI or surgery, and follow-up if intervention is not performed immediately

Once it has been established that the valve needs to be replaced, the next choice is between TAVI and surgical replacement. The 2025 European guidelines recommend TAVI in patients aged at least 70 years with tricuspid aortic valve stenosis, suitable anatomy and feasible transfemoral access; in patients under 70 years of age at low surgical risk, surgery remains the preferred choice. In all other cases, the Heart Team decides by considering anatomy, comorbidities, life expectancy, the need for other procedures and patient preferences.

If there is not yet an indication for intervention, surveillance must be active. In asymptomatic severe stenosis, the guidelines indicate reassessment at least every 6 months, or sooner if symptoms develop. The person should know which changes to report without waiting for the next visit: reduced exercise capacity, new dyspnea, chest pain, dizziness or syncope.

Frequently asked questions about when to intervene in aortic stenosis

When is intervention performed for aortic stenosis?
In symptomatic severe stenosis, intervention is generally recommended in eligible patients. It may also be indicated or considered in some severe forms without symptoms depending on ventricular function, exercise testing and other risk markers.

Which symptoms are most important?
Shortness of breath or reduced exercise capacity, chest pain, dizziness, presyncope and fainting are particularly relevant when the stenosis is severe.

Should severe stenosis without symptoms always just be monitored?
No. The 2025 guidelines allow early intervention to be considered in selected patients at low procedural risk, even when an exercise test confirms the absence of symptoms.

What does low flow and low gradient mean?
It means that the amount of blood passing through the valve is reduced and the gradient may be lower than expected. Additional tests are needed to determine whether the stenosis is truly severe.

Does intervention always mean surgery?
No. The valve can be replaced surgically or by TAVI. The choice depends on individual characteristics and should be discussed by the Heart Team.