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Domain

Valvular Heart Disease

Modules

Aortic Stenosis

Severe AS is not enough — symptoms, LV dysfunction, or exercise findings drive intervention.

Severity Grading

GradeVmaxMean gradientValve areaMild2.6–2.9 m/s<20 mmHg>1.5 cm²Moderate3.0–3.9 m/s20–39 mmHg1.0–1.5 cm²Severe≥4.0 m/s≥40 mmHg≤1.0 cm²Very severe≥5.0 m/s——Low-flow, low-gradient severe AS (reduced EF) requires dobutamine stress echo to confirm

Severe: Vmax ≥4.0 m/s, mean gradient ≥40 mmHg, AVA ≤1.0 cm². Very severe: Vmax ≥5.0. Low-flow low-gradient severe requires dobutamine stress echo.

Pathophysiology

StageLV wall / cavityEFSymptomsCompensatedConcentric hypertrophyNormalAbsentDecompensatedDilated cavityReducedAngina, syncope, HFSymptom onset, not LVEF, marks the transition and drives management

Progressive leaflet calcification narrows the aortic orifice, creating a fixed obstruction that imposes chronic pressure overload on the left ventricle. The LV compensates with concentric hypertrophy to normalize wall stress (Laplace's law), which preserves ejection fraction for years but raises filling pressures and impairs coronary flow reserve, causing subendocardial ischemia even without epicardial CAD. Once afterload mismatch exceeds the hypertrophic reserve, contractile function fails and the classic triad of angina, syncope, and heart failure emerges. This transition from compensated hypertrophy to decompensation is why symptom onset — not LVEF — drives the natural history.

Timing of AVR

Symptomatic severe AS?yesAVR — Class InoLVEF <50%?yesAVR — Class IIanoVery severe (Vmax≥5), abnormal exercisetest, rapid progression, or markedlyelevated BNP?Yes to any → AVR reasonable (Class IIa)No to all → continue surveillanceClass I: symptomatic severe AS. Asymptomatic LVEF <50% or undergoing other cardiac surgery. Class IIa: very severe (Vmax ≥5), abnormal exercise test, rapid progression, markedly elevated BNP.

TAVR vs SAVR

Age <65 or expectancy >20 years → SAVR (durability). Age ≥80 or high risk → TAVR. Age 65–80 → shared decision. Bicuspid, concomitant surgery → SAVR.

Low-Flow Low-Gradient AS

A low gradient with a small valve area can reflect either genuinely severe AS with reduced flow, or only moderate AS that looks severe because of low stroke volume — dobutamine stress echo or calcium scoring on CT can distinguish true-severe from pseudo-severe disease. This distinction changes management from surveillance to intervention.
Clinical pearls
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A well-preserved LV in severe AS is not reassuring — decompensation, once it occurs, is often rapid.
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Paradoxical low-flow low-gradient severe AS (normal EF, low stroke volume index) has a worse prognosis than high-gradient severe AS.
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Exercise testing is contraindicated in symptomatic severe AS but is reasonable in asymptomatic severe AS to unmask exertional symptoms, an abnormal BP response, or arrhythmia that reclassifies the patient as functionally symptomatic.
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AVR is reasonable (Class IIa) in asymptomatic severe AS with LVEF <60%, rapid hemodynamic progression, markedly elevated natriuretic peptides, or an abnormal exercise test — waiting for symptoms is not always the safest strategy.
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Exertional syncope in AS results from a fixed cardiac output that cannot rise with exercise-induced peripheral vasodilation, distinguishing it mechanistically from arrhythmic syncope.
Related guidelines