Aortic Stenosis

Risk factors

• Age (calcific/degenerative — atherosclerosis-like process)
• Congenital bicuspid aortic valve
• Rheumatic heart disease (less common in US, more in developing countries)
• Risk factors for atherosclerosis (HTN, DM, smoking, hyperlipidemia) accelerate calcific AS
• Chronic kidney disease (calcium-phosphate dysregulation)

Pathophysiology

Progressive valve calcification and fibrosis reduce orifice area. Increased afterload triggers compensatory LV hypertrophy (preserves stroke volume initially). Over years, LVH leads to diastolic dysfunction, increased oxygen demand (subendocardial ischemia → angina), and eventually systolic failure. The hypertrophied, stiff ventricle becomes preload-dependent — small drops in preload (nitrates, dehydration, hemorrhage) cause profound hypotension.

Clinical presentation

Differential diagnosis

• Aortic sclerosis — Aortic valve thickening WITHOUT obstruction; benign incidental finding; murmur present but valve area, gradient, and velocity normal; no symptoms
• Hypertrophic obstructive cardiomyopathy (HOCM) — Dynamic LVOT obstruction; murmur LOUDER with decreased preload (Valsalva strain, standing) — opposite of AS; family history of sudden cardiac death; septal LVH on echo
• Subvalvular AS (discrete membrane or muscular) — Younger patient, no aortic valve calcification on echo; obstruction visualized below the valve
• Supravalvular AS — Williams syndrome (elfin facies, hypercalcemia, intellectual disability); narrowing above sinotubular junction
• Mitral regurgitation — Holosystolic at apex, radiates to AXILLA (not carotids); intensity increases with handgrip (increased afterload)
• Pulmonic stenosis — Right-sided systolic murmur at LUSB; INCREASES with inspiration (Carvallo sign); often congenital
• Ventricular septal defect — Holosystolic at LSB with palpable thrill; murmur intensity inversely related to defect size

Diagnostic workup

Diagnostic algorithm

flowchart TD
  A[Severe AS<br/>AVA <1.0 cm²<br/>or mean gradient ≥40] --> B{Symptomatic?<br/>SAD: Syncope, Angina, Dyspnea}
  B -->|Yes| C[AVR indicated<br/>Class I]
  B -->|No| D{High-risk features?<br/>EF <50% / abnl exercise<br/>/ peak vel >5 m/s}
  D -->|Yes| C
  D -->|No| E[Monitor<br/>echo q6-12 mo]
  C --> F{Choose AVR<br/>modality}
  F --> G[SAVR<br/>younger, low risk,<br/>bicuspid + aortopathy]
  F --> H[TAVR<br/>elderly, high risk,<br/>prior CABG]
  G --> I{Valve type}
  I --> J[Mechanical<br/>lifetime warfarin]
  I --> K[Bioprosthetic<br/>limited AC, ~10-15 yr]

Treatment

Complications

• Sudden cardiac death — risk rises sharply once symptoms develop
• Heart failure (initially diastolic from LVH, then systolic)
• Atrial fibrillation (LA dilation)
• Conduction system disease — AV block (calcium extension into septum)
• Acquired von Willebrand syndrome (shear stress destroys vWF multimers → mucosal bleeding, GI angiodysplasia — Heyde syndrome)
• Post-AVR: prosthetic valve thrombosis, endocarditis, paravalvular leak

PANCE pearls

• AVOID NITRATES IN SEVERE AS — preload reduction across a fixed obstruction causes profound hypotension and syncope. This is a high-yield board pitfall.
• Heyde syndrome — triad of severe AS + GI angiodysplasia bleeding + acquired vWF deficiency. Bleeding resolves after AVR.
• Bicuspid AV is associated with aortic root dilation (~30%) — image the ascending aorta routinely; if >5 cm, consider concomitant aortic surgery.
• All patients with prosthetic valves need endocarditis prophylaxis for high-risk dental procedures (per AHA guidelines).
• Severe AS with reduced flow ('low-flow, low-gradient AS') can underestimate severity — dobutamine stress echo distinguishes true severe from pseudo-severe AS.

References

• ACC/AHA 2020 VHD — 2020 ACC/AHA Guideline for the Management of Patients with Valvular Heart Disease (Otto et al., Circulation 2021)
• PARTNER 1 — Transcatheter versus Surgical Aortic-Valve Replacement in High-Risk Patients (Smith et al., NEJM 2011)
• PARTNER 3 — TAVR with a Balloon-Expandable Valve in Low-Risk Patients (Mack et al., NEJM 2019)
• Evolut Low Risk — TAVR with a Self-Expanding Valve in Low-Risk Patients (Popma et al., NEJM 2019)