Aortic Stenosis

• Progressive LV pressure overload: The stenotic valve increases resistance to LV outflow, requiring the ventricle to generate supranormal systolic pressures to maintain cardiac output. This chronic pressure gradient (ΔP) triggers concentric left ventricular hypertrophy (LVH), initially a compensatory mechanism that maintains ejection fraction but eventually leads to diastolic dysfunction, impaired relaxation, and increased chamber stiffness.

• Cellular remodeling and fibrosis: Cardiomyocytes undergo hypertrophy with increased protein synthesis. Progressive interstitial and perivascular fibrosis develops, reducing coronary microvascular density and impairing diastolic filling. Eventually, systolic dysfunction ensues when the ventricle can no longer compensate for the chronic afterload increase.

• Energy depletion and ischemia: Despite normal epicardial coronaries, the hypertrophied myocardium experiences subendocardial ischemia due to increased oxygen demand (elevated wall stress and heart rate) combined with relatively fixed coronary blood flow. This ischemia is exacerbated during exercise or tachycardia, explaining anginal symptoms even without coronary artery disease.

• Hemodynamic decompensation: Once the ventricle fails, there is a paradoxical decrease in the transaortic gradient despite worsening AS (low-flow, low-gradient AS). Elevated LV end-diastolic pressure is transmitted backward to the left atrium and pulmonary circulation, causing pulmonary hypertension, right ventricular strain, and eventually right heart failure.

• Arrhythmia substrate: LVH and fibrosis create electrical heterogeneity predisposing to atrial fibrillation (AF), which may precipitate acute decompensation by loss of atrial "kick" in stiff ventricles dependent on atrial contribution for filling.

• Bicuspid aortic valve: The most common congenital abnormality (1-2% of population), presenting with AS typically 10-20 years earlier than tricuspid valve disease; accounts for ~50% of AS cases requiring intervention before age 60.

• Degenerative calcific AS: Progressive calcium deposition on a morphologically normal tricuspid valve, increasingly prevalent with aging, hypertension, chronic kidney disease, and elevated Lp(a); now the leading cause of AS in elderly populations.

• Rheumatic heart disease: More common in developing nations and immigrants; typically causes mixed aortic lesions (stenosis + regurgitation) and often involves mitral valve; associated with history of acute rheumatic fever.

• Age: Exponential increase in prevalence after age 60; sclerotic changes occur in up to 25% of those >65 years.

• Chronic kidney disease (CKD): Accelerates calcific AS through phosphate-calcium dysregulation and upregulation of bone-forming genes in valve tissue.

• Elevated Lp(a): Independent genetic risk factor strongly associated with accelerated calcific AS; considered for future targeted therapy.

• Hypertension: Chronic pressure load increases risk; paradoxically may blunt symptom development by maintaining higher cardiac output.

• Inflammatory conditions: Infective endocarditis (causes acute AS), systemic lupus erythematosus, Marfan syndrome (with aortic root involvement), radiation (post-chest radiation therapy).

• Exertional dyspnea: Most common initial symptom; results from exertional increase in LV diastolic pressure and subsequent pulmonary edema; often presents as dyspnea on exertion (DOE) that worsens predictably with activity.

• Exertional angina: Occurs even without coronary stenosis; caused by demand ischemia from LVH with subendocardial ischemia; classically substernal, exertional, relieved by rest.

• Syncope or presyncope: "Exertional syncope" is a classic red flag; caused by failure of cardiac output to rise appropriately with exercise and/or vasodilation in exercising muscles that drop systemic vascular resistance in the setting of fixed obstruction; indicates severe disease.

• Palpitations: Often related to atrial fibrillation (common arrhythmia in AS) or from forceful apical impulse.

• Fatigue and reduced exercise tolerance: Subtle early symptom reflecting inability to increase stroke volume appropriately.

• Harsh, late-peaking systolic ejection murmur: Loudest at right upper sternal border (aortic area) with radiation to carotids; increases with maneuvers that increase afterload (handgrip, squatting) and decreases with reduced preload (Valsalva, standing); the "late-peaking" or "diamond-shaped" quality reflects prolonged ejection time as stenotic valve restricts flow.

• Diminished and delayed carotid pulse (pulsus parvus et tardus): Reflects reduced stroke volume and prolonged ejection time; more apparent in severe disease.

• Paradoxical splitting of S₂: P₂ occurs after A₂ (reversed from normal) due to prolonged LV ejection time; S₂ may become single in severe AS.

• Systolic ejection click: Present in bicuspid aortic valve (earlier click reflects limited valve opening); absent in calcific AS where leaflets are immobile—an important distinguishing feature.

• Forceful apical impulse (hyperdynamic apex): Reflects LVH and increased contractility; may be sustained rather than brief.

• S₄ (atrial gallop): Reflects reduced LV compliance from LVH; prominent in many patients.

• Signs of heart failure: Pulmonary edema (rales), peripheral edema, elevated JVP, hepatomegaly—indicate decompensated disease.

• Asymptomatic disease: Many patients, particularly with moderate stenosis, remain asymptomatic for years; found incidentally on exam or imaging.

• Transthoracic echocardiography: Gold standard for diagnosis and severity grading; provides:
• Aortic valve area (AVA) by planimetry (most accurate) or continuity equation [AVA = (LVOT area × LVOT VTI) / AVA VTI]
• Peak transaortic gradient (ΔP) and mean gradient
• Peak aortic jet velocity
• Presence and severity of LVH
• LV systolic function (ejection fraction)
• Diastolic function parameters
• Valve morphology (bicuspid vs. tricuspid, degree of calcification)

• Severity classification (by multiple parameters; at least 2 must concordantly indicate severity):
• Mild AS: AVA 1.5-2.0 cm², mean ΔP <25 mmHg, peak velocity <3.0 m/s
• Moderate AS: AVA 1.0-1.5 cm², mean ΔP 25-40 mmHg, peak velocity 3.0-4.0 m/s
• Severe AS: AVA <1.0 cm² (critical if <0.6 cm²), mean ΔP ≥40 mmHg, peak velocity ≥4.0 m/s
• Low-flow, low-gradient severe AS: AVA <1.0 cm² with mean ΔP <40 mmHg and reduced ejection fraction (EF <50%) or low flow state; requires dobutamine stress echo to differentiate true severe AS (unchanged AVA with increased gradient with increased contractility) from pseudosevere AS.

• Electrocardiography (ECG): Shows LVH with strain pattern (increased QRS voltage, ST depression in lateral leads); may show atrial fibrillation, AV block (in calcific disease with conduction system involvement), or nonspecific ST-T changes.

• Chest X-ray: Demonstrates aortic valve calcification (may be absent in young bicuspid valve disease), LVH with apical displacement, signs of pulmonary edema if decompensated.

• Stress testing (exercise echo or treadmill with ECG):
• Symptom-limited stress testing in asymptomatic severe AS or ambiguous symptoms to provoke symptoms or detect ischemia
• Dobutamine stress echo for low-flow, low-gradient AS
• Contraindicated in symptomatic severe AS (risk of hemodynamic collapse)

• Cardiac catheterization:
• Indicated when noninvasive data are incongruent (e.g., severe AS on echo but no symptoms)
• Invasive pressure gradients measured across aortic valve; directly measured AVA via Gorlin equation
• Coronary angiography to assess for coexisting CAD before surgical valve replacement in patients >40 years or with CAD risk factors
• Not routine for diagnosis but essential for hemodynamic assessment when clinical picture is unclear

• CT angiography:
• Aortic valve calcium scoring via CT correlates with disease severity; used for risk stratification in borderline cases
• Assessment of aortic root diameter and anatomy (essential before transcatheter aortic valve implantation [TAVI])
• Can measure AVA by planimetry

• Medical management for asymptomatic severe AS and mild-to-moderate AS:
• ACE inhibitors or ARBs: Theoretically reduce LVH and fibrosis progression; evidence limited but reasonable for hypertensive patients
• Statins: No mortality benefit in AS; may slow progression in calcific disease (ongoing investigation)
• Avoid diuretics unless heart failure present; excessive volume depletion may cause hemodynamic collapse
• Avoid negative inotropes (beta-blockers, non-dihydropyridine calcium channel blockers); maintain adequate preload and contractility
• Adequate rate control if atrial fibrillation develops; digoxin preferred over beta-blockers for symptomatic patients

• Surgical aortic valve replacement (SAVR):
• Indications for SYMPTOMATIC severe AS:
• All symptomatic patients (angina, syncope, dyspnea) with confirmed severe AS
• Symptomatic low-flow, low-gradient AS with reduced EF after dobutamine stress echo documents true severe AS
• Indications for ASYMPTOMATIC severe AS:
• Ejection fraction <50% (LV dysfunction from AS burden)
• Abnormal exercise response (lack of symptom development despite hemodynamic criteria for severe AS, but with hypotensive response or excessive ST-segment depression)
• Severe LVH (LV mass >140 g/m² in women, >110 g/m² in men)
• Very severe AS (AVA <0.6 cm², peak gradient ≥60 mmHg, or velocity ≥5.0 m/s) with additional risk factors
• Bioprosthetic valves generally used in modern practice; durability 10-15 years (longer in elderly); structural valve deterioration (SVD) less common with newer tissue valves
• Mechanical valves reserved for younger patients (<60 years) or those with contraindications to anticoagulation; require lifelong anticoagulation with warfarin (INR 2-3 for aortic position) or newer direct oral anticoagulants (limited data)

• Transcatheter aortic valve implantation (TAVI):
• Expanding role as technology improves and indications expand
• Current guidelines favor TAVI over SAVR in patients with high/prohibitive surgical risk
• Lower-risk patients: Recent trials (PARTNER 3, EVOLUT Low Risk) show TAVI noninferior or superior to SAVR; now often preferred as first-line in selected anatomically suitable candidates
• Technical considerations: Requires careful assessment of aortic root anatomy (diameter, calcification, distance to coronary ostia), femoral access, and paravalvular leak risk
• Advantages: Minimally invasive, shorter recovery, immediate hemodynamic benefit
• Disadvantages: Paravalvular aortic regurgitation (5-30% mild-moderate, 1-5% severe), conduction disturbances requiring pacemaker (10-30%), valve durability data still evolving

• Non-pharmacological measures:
• Activity restriction: Patients with symptomatic severe AS should avoid strenuous exertion, competitive sports, and sudden increases in activity; sudden cardiac death can occur with exertion
• Endocarditis prophylaxis: No longer routinely recommended except for patients with prior endocarditis or complex cyanotic heart disease
• Dental hygiene and infection prevention: Important as bacteremia can seed diseased valve
• Hemodynamic optimization: Maintain adequate blood pressure; avoid acute volume depletion; manage anemia if present

• Monitoring and follow-up:
• Asymptomatic mild AS: Echocardiography every 3-5 years
• Asymptomatic moderate AS: Echocardiography every 1-2 years
• Asymptomatic severe AS: Echocardiography every 6-12 months, plus regular clinical assessment and exercise testing if feasible
• Post-SAVR or TAVI: Serial echos to assess prosthetic function, structural deterioration, and paravalvular regurgitation; anticoagulation management for mechanical valves

• Sudden cardiac death: Occurs in 1-2% annually in asymptomatic severe AS; mechanism includes arrhythmia (AF, ventricular arrhythmia from myocardial scar), acute hemodynamic collapse, or demand ischemia; exertional syncope is a harbinger.

• Acute decompensated heart failure: Precipitants include development of atrial fibrillation (loss of atrial contribution in noncompliant ventricle), acute increase in afterload (hypertensive crisis), anemia, infection, or worsening renal function; presents as acute pulmonary edema; requires urgent valve replacement or TAVI.

• Atrial fibrillation: Occurs in 10-20% of AS patients; related to LVH, elevated LA pressure, and fibrosis; increases stroke risk and may precipitate decompensation; requires rate control and anticoagulation.

• Infective endocarditis: Risk increased 3-5 fold in AS (especially if bicuspid); can accelerate AS progression; diagnosed by blood cultures, TEE (transesophageal echo shows vegetation); treatment requires antibiotics plus often urgent surgical intervention for large vegetations, abscess, or acute severe regurgitation.

• Aortic regurgitation (AR): Secondary AR develops from progressive valve deformation and annular dilation; severe AR may require earlier intervention; endocarditis is common cause of acute severe AR requiring emergent surgery.

• Stroke and thromboembolic events: Increased risk from AF, endocarditis with septic emboli, or prosthetic valve thrombosis (mechanical valve if inadequately anticoagulated).

• Prosthetic valve dysfunction:
• Structural valve deterioration (SVD): Bioprosthetic valve degeneration; risk increases after 5-10 years; managed by repeat valve replacement or TAVI-in-SAVR
• Paravalvular leak (TAVI-related): Can cause AR and hemolysis; may require percutaneous closure device or repeat intervention
• Prosthetic valve thrombosis: Mechanical valve in low-flow state or subtherapeutic anticoagulation; causes sudden increase in gradients; managed with thrombolysis or thrombectomy
• Pannus formation: Overgrowth of connective tissue around mechanical valve leading to obstruction; may require reoperation

• Coronary ischemia and myocardial infarction:

Buzzwords that name the diagnosis

• The triad: angina, syncope, dyspnea ("SAD") on exertion — symptom onset marks a sharp inflection in survival, and untreated symptomatic severe AS carries a high short-term mortality.
• Physical exam severity markers: pulsus parvus et tardus, late-peaking murmur, soft or absent A₂ (single S₂), and a sustained apical impulse with S₄. A loud murmur is not a severity marker; a late-peaking, soft-A₂ murmur is.
• Gallavardin phenomenon: the AS murmur radiating to the apex mimics mitral regurgitation — the distractor. True MR is holosystolic and radiates to the axilla.

The one maneuver question

• AS vs HOCM: AS murmur decreases with Valsalva/standing (less preload) and increases with squatting/handgrip. HOCM does the opposite (increases with Valsalva/standing). This single contrast is tested repeatedly.

Single best next step

• Transthoracic echocardiography for any suspected AS — never exercise stress testing in symptomatic severe AS (risk of hemodynamic collapse). Per the ACC/AHA 2020 Valvular Heart Disease Guideline, symptomatic severe AS is a Class 1 indication for aortic valve replacement; choice of SAVR versus TAVR is age- and risk-based with shared decision-making (SAVR generally favored in younger patients, TAVR favored in the elderly or high surgical risk).

Associations examiners love

• Bicuspid aortic valve: linked to coarctation of the aorta, Turner syndrome, and ascending aortic dilation/dissection — screen the aorta, not just the valve.
• Heyde syndrome: AS + GI bleeding from colonic angiodysplasia due to shear-mediated loss of high-molecular-weight von Willebrand multimers (acquired vWD); typically resolves after valve replacement.

Distractors to avoid

• Vasodilators/nitrates in severe AS: preload and afterload reduction against a fixed obstruction can precipitate profound hypotension — a classic wrong answer in the chest-pain stem.
• Statins do not halt AS progression; prescribe them for ASCVD indications only.
• Balloon valvuloplasty is palliative/bridging in calcific adult AS — definitive only in congenital AS of children and young adults.
• New AV block in an elderly patient with calcific AS reflects calcium extending into the conduction system, and pacemaker need is also a recognized post-TAVR issue.