Recommended Workup for Suspected Aortic Stenosis
The recommended workup for a patient with suspected aortic stenosis should begin with transthoracic echocardiography, which is the cornerstone diagnostic test for confirming the diagnosis and assessing severity. 1
Initial Evaluation
- Physical examination findings that suggest aortic stenosis include a systolic ejection murmur, single or paradoxically split S2, and delayed/diminished carotid upstroke, though these may be less reliable in elderly patients 1
- Transthoracic echocardiography (TTE) is the primary diagnostic tool for confirming AS and should be performed when there is a systolic murmur grade 3/6 or greater, a single S2, or symptoms potentially attributable to AS 1
Echocardiographic Assessment
The three primary hemodynamic parameters to evaluate during echocardiography are:
- AS peak jet velocity: A peak velocity ≥4 m/s is consistent with severe AS; should be obtained from multiple acoustic windows using a dedicated small dual-crystal CWD transducer 1
- Mean transvalvular pressure gradient: A mean gradient ≥40 mmHg indicates severe AS 1
- Aortic valve area (AVA) calculated by the continuity equation: An AVA <1.0 cm² indicates severe AS 1
Additional echocardiographic assessments should include:
- Left ventricular wall thickness, size, and function 1
- LVOT diameter measurement in parasternal long-axis view 1
- Valve morphology and calcification 1
- Assessment of other associated valvular disease 1
Classification of Aortic Stenosis Severity
| Parameter | Mild | Moderate | Severe |
|---|---|---|---|
| Peak velocity (m/s) | 2.6-2.9 | 3.0-4.0 | ≥4.0 |
| Mean gradient (mmHg) | <20 | 20-40 | ≥40 |
| AVA (cm²) | >1.5 | 1.0-1.5 | <1.0 |
| Indexed AVA (cm²/m²) | >0.85 | 0.60-0.85 | <0.6 |
| Velocity ratio | >0.50 | 0.25-0.50 | <0.25 |
Special Considerations for Discordant Findings
When there is discrepancy between valve area and gradient measurements:
Low flow, low gradient AS with reduced ejection fraction (AVA <1.0 cm², mean gradient <40 mmHg, EF <50%, SVi <35 mL/m²):
- Low-dose dobutamine stress echocardiography (DSE) is recommended to distinguish true severe AS from pseudosevere AS 1
- Protocol starts at 2.5-5 μg/kg/min with incremental increases every 3-5 minutes to maximum 10-20 μg/kg/min 1
- Severe AS is confirmed if velocity reaches ≥4 m/s or mean gradient ≥30-40 mmHg while AVA remains <1.0 cm² 1
Low flow, low gradient AS with preserved ejection fraction (AVA <1.0 cm², mean gradient <40 mmHg, EF ≥50%, SVi <35 mL/m²):
Additional Testing When Indicated
- Exercise testing may be considered in asymptomatic patients to elicit exercise-induced symptoms and abnormal blood pressure responses (but should NOT be performed in symptomatic patients) 1
- Multislice computed tomography (MSCT) for valve calcification assessment when echocardiographic findings are discordant 1
- Cardiac magnetic resonance (CMR) for flow assessment and LV function evaluation when echocardiographic images are suboptimal 1
Follow-up Recommendations
- Asymptomatic severe AS: Echocardiography every year 1
- Moderate AS: Echocardiography every 1-2 years 1
- Mild AS: Echocardiography every 3-5 years 1
Common Pitfalls to Avoid
- Underestimation of jet velocity due to non-parallel intercept angle between ultrasound beam and high-velocity jet 1
- Inaccurate LVOT diameter measurement leading to errors in AVA calculation; consider direct planimetry of LVOT by 3D TEE or MSCT 1
- Failure to normalize blood pressure before assessment, as hypertension can alter velocity/gradient measurements 1
- Overlooking concurrent conditions that may affect interpretation (e.g., mitral regurgitation, aortic regurgitation) 1
- Misclassification of severity when there are discordant findings between AVA and gradient 1
Referral Recommendations
Cardiology referral is recommended for:
- All patients with symptomatic moderate and severe AS
- Patients with severe AS without apparent symptoms
- Patients with AS and left ventricular systolic dysfunction 2