Aortic Stenosis Severity Algorithm

Aortic Stenosis Severity Algorithm (ACC/AHA 2020 Guidelines)

Step 1: Assess Aortic Valve Morphology and Function

• Check for bicuspid vs. tricuspid valve anatomy.
• Evaluate leaflet mobility, calcification, and commissural fusion on echocardiography.

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Step 2: Quantify AS Severity (Echocardiographic Parameters)

• Aortic Valve Area (AVA) = (LVOT Area × LVOT VTI) / Aortic VTI
• Mean Transvalvular Gradient (TVG)
• Peak Aortic Jet Velocity (Vmax)
• Dimensionless Index (DI) = LVOT VTI / Aortic VTI

Severity	AVA (cm²)	Mean Gradient (mmHg)	Peak Velocity (m/s)	Dimensionless Index (DI)
Mild	>1.5	<20	<3.0	>0.5
Moderate	1.0 – 1.5	20-39	3.0 – 3.9	0.25 – 0.5
Severe	<1.0	≥40	≥4.0	<0.25
Very Severe	<0.6	≥60	≥5.0	<0.25

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Step 3: Identify Low-Flow, Low-Gradient Severe AS

If AVA <1.0 cm² but Mean Gradient <40 mmHg, further assessment is required:

1. Low EF (<50%)?
   • Perform Dobutamine Stress Echo (DSE):
     • If Vmax ≥4.0 m/s or Mean Gradient ≥40 mmHg: True Severe AS
     • If AVA increases >1.0 cm² with little gradient rise: Pseudosevere AS
2. Preserved EF but Suspected Paradoxical Low-Flow AS?
   • Assess Stroke Volume Index (SVI):
     • SVI <35 mL/m² → Consider low-flow, low-gradient AS.
   • Look for concentric LVH and small LV cavity.
   • CT Calcium Scoring (Men >2000 AU, Women >1200 AU supports severe AS).

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Step 4: Determine Need for Intervention Based on Symptoms & Severity

A. Symptomatic Severe AS (Class I Indications for Valve Replacement)

TAVR/SAVR is recommended if:

• Severe AS + Symptoms (Dyspnea, Syncope, Angina).
• Severe AS + EF <50%.
• Severe AS + Abnormal Exercise Test (BP drop, symptoms).

B. Asymptomatic Severe AS: When to Consider Early Surgery (Class IIa/IIb Indications)

• Very Severe AS (Vmax ≥5.0 m/s or Mean Gradient ≥60 mmHg).
• Rapid progression of AS (Vmax increase ≥0.3 m/s per year).
• Severe AS + Elevated BNP levels (suggestive of LV dysfunction).
• Severe AS + Severe LVH, Pulmonary Hypertension, or LA Enlargement.

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Step 5: Choose the Appropriate Intervention

Patient Profile	Recommended Intervention
Age ≥65, High Surgical Risk	TAVR (Preferred)
Age <65, Low Surgical Risk	SAVR (Preferred)
Severe AS + CAD Requiring CABG	SAVR + CABG
Severe AS + Low Flow, Low Gradient	TAVR/SAVR if True Severe AS
Frailty, Comorbidities, Limited Life Expectancy	Medical Management

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Key Takeaways from ACC/AHA Guidelines

1. Symptomatic Severe AS → Always replace the valve.
2. Asymptomatic Severe AS → Consider intervention based on high-risk features.
3. Low-Flow, Low-Gradient AS → Confirm severity before intervention.
4. TAVR preferred in elderly/high-risk patients, SAVR in younger/low-risk patients.