What are the stages and treatment approaches for aortic stenosis?

Aortic Stenosis Staging

Aortic stenosis is classified into stages A through D based on valve anatomy, hemodynamics, left ventricular function, and symptom status, with Stage D patients requiring aortic valve replacement and earlier stages managed with surveillance. 1

Stage A: At Risk

• Patients have risk factors for developing AS but no hemodynamic obstruction 1
• Includes bicuspid aortic valve or aortic sclerosis with AVA >1.0 cm² and mean gradient <40 mmHg 1
• No indication for aortic valve replacement; surveillance every 3-5 years with echocardiography 1, 2

Stage B: Progressive AS (Mild to Moderate)

• Mild to moderate hemodynamic obstruction without symptoms 1
• AVA ≥1.0 cm² with mean gradient <40 mmHg but evidence of progressive valve calcification 1
• No indication for aortic valve replacement; echocardiographic surveillance every 1-2 years for moderate disease, every 3-5 years for mild disease 1, 2

Stage C: Asymptomatic Severe AS

Stage C1: High-Gradient Severe AS (Asymptomatic)

• AVA ≤1.0 cm² with mean gradient ≥40 mmHg or peak velocity ≥4.0 m/s 1
• LVEF >50% and no symptoms on careful questioning 1
• Class IIa indication for AVR if peak velocity ≥5.0 m/s, abnormal exercise test, or rapid progression 1
• Risk stratification markers warranting closer follow-up (every 3 months): severe aortic valve calcification on CT, global longitudinal strain <16%, indexed stroke volume <35 mL/m², elevated BNP (>2x normal for age/sex), or >18-20 mmHg increase in mean gradient with exercise 1

Stage C2: Severe AS with LV Dysfunction (Asymptomatic)

• AVA ≤1.0 cm² with LVEF <50% without other cause 1
• Class I indication for AVR regardless of gradient 1

Stage C3 (HAVEC Classification): Paradoxical Low-Flow Low-Gradient AS (Asymptomatic)

• AVA ≤1.0 cm², indexed AVA ≤0.6 cm²/m², mean gradient <40 mmHg, LVEF ≥50%, stroke volume index <35 mL/m² 1
• Small hypertrophied LV with restrictive physiology despite preserved ejection fraction 3
• Requires confirmation of severity with aortic valve calcium scoring by CT (men ≥3000 AU, women ≥1600 AU) or dobutamine stress echo 1, 3
• Conservative management with close surveillance every 6 months; Class IIa intervention only after careful confirmation of severity if symptoms develop 3

Stage C4 (HAVEC Classification): Normal-Flow Low-Gradient AS (Asymptomatic)

• AVA ≤1.0 cm², mean gradient <40 mmHg, LVEF ≥50%, stroke volume index ≥35 mL/m² 1
• Up to 50% may have true severe AS when assessed by CT calcium scoring 1
• Requires multimodality imaging (CT calcium scoring or stress echo) to confirm severity before intervention 1

Stage D: Symptomatic Severe AS

Stage D1: High-Gradient Symptomatic Severe AS

• AVA ≤1.0 cm² with mean gradient ≥40 mmHg or peak velocity ≥4.0 m/s 1
• Symptoms of heart failure, angina, or syncope 1
• Class I indication for AVR (surgical or TAVR depending on surgical risk); average survival only 2-3 years without treatment 1

Stage D2: Classical Low-Flow Low-Gradient Severe AS

• AVA ≤1.0 cm², mean gradient <40 mmHg, LVEF <50%, severely calcified valve 1
• Characterized by depressed LV systolic function and eccentric remodeling 1
• Requires dobutamine stress echo to differentiate true severe AS (velocity increases to ≥4.0 m/s) from pseudosevere AS 1
• If dobutamine shows lack of flow reserve, indicates very poor prognosis with either medical or surgical therapy 3
• If true severe AS confirmed: Class IIa indication for AVR, though high surgical risk 1
• Alternative confirmation: CT calcium scoring (men >2000 AU, women >1200 AU) if dobutamine not feasible 1

Stage D3: Paradoxical Low-Flow Low-Gradient Symptomatic Severe AS

• AVA ≤1.0 cm², indexed AVA ≤0.6 cm²/m², mean gradient <40 mmHg, LVEF ≥50%, stroke volume index <35 mL/m² 1
• Most challenging diagnosis; must confirm hemodynamics when normotensive and exclude other causes of symptoms 1
• Requires CT calcium scoring (men ≥3000 AU, women ≥1600 AU) to confirm anatomic severity 3
• Consider 3D TEE or cardiac CT for alternative AVA measurement, as 2D echo frequently underestimates LVOT diameter in small hypertrophied ventricles 3
• Class IIa indication for AVR only after careful confirmation that AS is severe and symptoms are attributable to AS 1

Stage D4 (HAVEC Classification): Normal-Flow Low-Gradient Symptomatic Severe AS

• AVA ≤1.0 cm², mean gradient <40 mmHg, LVEF ≥50%, stroke volume index ≥35 mL/m² 1
• Requires multimodality imaging to confirm severity before intervention 1

Treatment Algorithm by Stage

Stages A and B: No AVR indicated; surveillance only 1

Stage C1: Class IIa AVR if very severe (peak velocity ≥5.0 m/s), abnormal exercise test, or multiple high-risk features; otherwise watchful waiting with close follow-up 1

Stage C2: Class I AVR regardless of symptoms 1

Stages C3/C4: Confirm severity with multimodality imaging; conservative management unless high-risk features present 1, 3

Stage D1: Class I AVR (surgical or TAVR based on surgical risk) 1

Stage D2: Confirm severity with dobutamine stress echo or CT calcium scoring; Class IIa AVR if true severe AS confirmed 1

Stage D3: Confirm severity with CT calcium scoring; Class IIa AVR only after careful confirmation 1, 3

Common Pitfalls

• Do not dismiss low gradients as "moderate" stenosis in low-flow states (Stages D2, D3)—gradients underestimate anatomic severity when flow is reduced 3
• Do not rely solely on AVA calculations from 2D echo in paradoxical low-flow AS—LVOT diameter measurement errors are extremely common and lead to overestimation of stenosis severity 3
• Do not assume asymptomatic patients are truly asymptomatic without formal exercise testing—many patients unconsciously limit activity 1
• In Stage D2, a stroke volume index <30 mL/m² carries particularly poor prognosis and requires urgent heart team discussion 3