What is aortic stenosis?

Aortic stenosis (AS) is the most prevalent valvular heart disease in adults in developed countries, affecting approximately 3–5% of people over 65 years. It involves progressive narrowing of the aortic valve orifice, obstructing blood flow from the left ventricle into the aorta. The natural history is a long asymptomatic phase followed by rapid clinical deterioration once symptoms emerge.

Severity classification

The classic symptomatic triad

Causes

• Calcific (degenerative) AS: Most common. Progressive calcium deposition on valve leaflets with age. Shares risk factors with atherosclerosis (hypertension, diabetes, dyslipidaemia, smoking).
• Bicuspid aortic valve (BAV): Congenital — present in ~1% of population. BAV undergoes accelerated calcification; AS often presents 10–15 years earlier than tricuspid valve AS.
• Rheumatic AS: Post-inflammatory scarring of valve leaflets. Now rare in Australia but prevalent in developing countries.

• Echocardiogram (TTE): The cornerstone investigation. Quantifies AVA, mean gradient, peak velocity, and left ventricular ejection fraction and wall thickness.
• Stress echocardiography: For patients with 'low-flow, low-gradient' AS to differentiate true-severe from pseudo-severe AS.
• CT cardiac: Aortic valve calcium score (AVC) confirms anatomically severe AS when Doppler measurements are discordant. Also used pre-TAVI planning.
• ECG: May show left ventricular hypertrophy (LVH) or left bundle branch block.
• 6-minute walk test: Objective exercise assessment in patients with 'asymptomatic' severe AS.
• BNP/NT-proBNP: Rising levels in asymptomatic severe AS may indicate need for earlier intervention.

Medical management

There is no proven medication to slow AS progression. Management focuses on risk factor control and surveillance:

• Treat hypertension, dyslipidaemia and diabetes
• ACE inhibitors for LV dysfunction
• Diuretics for congestion
• Avoid excessive exertion in severe AS prior to intervention

Valve replacement — indications

• Symptomatic severe AS — Class I indication (urgent)
• Asymptomatic severe AS with LVEF <50%
• Asymptomatic severe AS undergoing cardiac surgery for another reason
• Very severe AS (Vmax >5 m/s) or rapidly progressing — may justify early intervention
• Asymptomatic severe AS with declining exercise capacity or rising BNP

SAVR vs TAVI

• Surgical AVR (SAVR): Standard treatment for low-to-intermediate risk patients <75 years. Mechanical or bioprosthetic valve.
• TAVI (Transcatheter Aortic Valve Implantation): Catheter-based valve deployment via the femoral artery. Now approved for intermediate and low-risk patients. Preferred in patients ≥75 years or those with high surgical risk.

• After successful valve replacement, symptoms typically resolve rapidly
• Survival after TAVI/SAVR approaches that of an age-matched general population
• BAV patients require lifelong aortic root/ascending aorta surveillance with imaging
• Mild-moderate AS requires annual clinical review and echocardiography every 1–3 years
• Regular specialist review allows timely referral for intervention before irreversible LV damage