Cardiovascular · Topic 29 of 48

Aortic Stenosis

Cardiovascular · valvular heart disease

Aortic Stenosis

A fixed outflow obstruction. Severe AS means velocity ≥ 4 m/s; once angina, syncope or heart failure appears, replace the valve — and protect preload until then.

Key numbers

Severe AS: velocity ≥ 4 m/sVmax ≥ 4 m/s, MG ≥ 40

Angina, syncope, heart failure~3 yr once symptomatic

Replace the valve once symptomaticor LVEF < 50%

01 · Defined bySevere AS: velocity ≥ 4 m/s

Severe AS = peak aortic velocity ≥ 4 m/s or mean gradient ≥ 40 mmHg (valve area typically ≤ 1.0 cm²); very severe = velocity ≥ 5 m/s or mean gradient ≥ 60 mmHg.

02 · Look forAngina, syncope, heart failure

Severe AS presents with exertional angina, exertional syncope and dyspnea or heart failure; once symptoms begin, mean survival without valve replacement falls to about 3 years and sudden death can occur.

03 · DoReplace the valve once symptomatic

Replace the valve in severe AS with symptoms (by history or exercise testing) or LVEF < 50%; it is reasonable if exercise testing shows poor tolerance or a systolic BP fall ≥ 10 mmHg.

Causes & risk factors

Why it happens

Calcific degeneration in older adults; bicuspid valve youngerCalcific degeneration (preceded by aortic sclerosis) causes most AS in older adults, a congenital bicuspid valve causes most AS under age 70, and rheumatic disease predominates in low-resource countries.

Bicuspid valve: screen the aortaA bicuspid aortic valve is associated with coarctation and progressive ascending aortic dilation that can cause dissection; first-degree relatives should be screened with echo.

Presentation

What you'll see

Crescendo-decrescendo murmur radiating to carotids must knowHallmark: a harsh crescendo-decrescendo systolic ejection murmur at the upper sternal borders radiating to the carotids, with a weak, delayed carotid pulse (pulsus parvus et tardus) and a soft or single S2.

Management

Orders

Low-gradient AS: dobutamine echoWith reduced EF, velocity can be < 4 m/s despite a valve area ≤ 1.0 cm² (low-flow, low-gradient AS); low-dose dobutamine echo separates true severe AS, which benefits from replacement, from pseudo-stenosis.

Coronary evaluation before valve replacementEvaluate for coronary artery disease before aortic valve replacement (usually catheterization) so CABG can be done in the same operation when indicated.

Red flags & don'ts

Avoid harm

Preload dependent: avoid nitrates and hypovolemia avoidSevere AS is preload dependent with a fixed outflow obstruction: use nitrates and vasodilators cautiously, avoid hypovolemia, hypotension and tachycardia, keep sinus rhythm, and raise a falling BP with phenylephrine or norepinephrine.

No exercise testing if symptomatic avoidIn asymptomatic severe AS, a supervised exercise test can unmask symptoms or a blood pressure fall (an indication for replacement); exercise testing is contraindicated in symptomatic AS.

TAVR: watch for heart block and leak complicationCompared with surgery, transfemoral TAVR has lower early mortality, stroke and bleeding but more vascular complications, paravalvular regurgitation and need for a permanent pacemaker.

The rules

Know these

SAVR under 65, TAVR over 80Valve choice (2020 ACC/AHA): surgical replacement under 65 or life expectancy > 20 years; transfemoral TAVR over 80 or life expectancy < 10 years; shared decision from 65 to 80.

Aortic stenosis or hypertrophic cardiomyopathy murmur?

Commonly confused

Squatting	Louder
Passive leg raise	Louder
Valsalva strain	Softer

More detail

Reference

Show 9 reference facts

In decompensated heart failure before valve replacement, nitroprusside has been used as a temporizing afterload reducer; patients too high risk for intervention get cautious diuretics, digoxin and ACE inhibitors.

With low surgical risk, replacement is reasonable in asymptomatic severe AS with velocity ≥ 5 m/s, BNP > 3 times normal, or velocity rising ≥ 0.3 m/s per year.

Asymptomatic severe AS with normal LV function needs reassessment about every 6 months; about 13% of deaths in severe AS are sudden, so advise limiting heavy exertion.

Balloon aortic valvuloplasty is mainly for congenital AS in the young; in older adults it is only a temporary bridge because of high complication and restenosis rates.

A normally split S2 is the only physical finding that reliably excludes severe AS; a softer, shorter murmur can mean a failing ventricle, not milder stenosis.

Heyde syndrome: shear stress across the stenotic valve degrades von Willebrand multimers, causing GI bleeding from angiodysplasia that usually resolves after valve replacement.

CT aortic valve calcium score makes severe AS likely above 2000 Agatston units in men and 1300 in women, helping when echo measurements disagree.

Statins do not slow AS progression; elevated lipoprotein(a) predicts faster hemodynamic progression.

Pressure overload causes concentric LV hypertrophy without dilation; when the ventricle finally fails, EF and gradient fall together (low-gradient severe AS).

Pearl

Angina, syncope, heart failure: once a patient with severe AS has symptoms, the clock is running — mean survival without valve replacement is about 3 years.

Sources · Merck Manual Professional — Aortic Stenosis · Otto CM et al. 2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease. Circulation 2021;143:e72–e227 (full text, STS-hosted PDF) · Merck Manual Professional — Aortic Regurgitation · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).