MedCram Lecture: Aortic Stenosis

Introduction

• Focus: Pathology, pathophysiology, and clinical aspects of aortic stenosis.
• Anatomy Review:
  • Blood flows from right atrium → tricuspid valve → right ventricle → pulmonic valve → lungs → left atrium → mitral valve → left ventricle → aortic valve → body.
  • Aortic Valve: Focus of aortic stenosis.

Aortic Stenosis

• Definition: Inability of the aortic valve to open fully, leading to obstruction of blood flow.

Causes by Age Group

• <30 Years: Rare, often due to calcification of a unicomisural valve.
• 30-70 Years: Most common cause is bicuspid aortic valve, leading to early calcification.
• >70 Years: Calcification of a normal tricuspid valve.

Pathophysiology

• Pressure Effects: Increased pressure in left ventricle, leading to hypertrophy.

  • Decreased Compliance: Stiff ventricle, high pressure needed for volume changes.
  • Increased Left Atrial Pressure: Pressure transmitted back to lungs, leading to systemic venous hypertension.

• Oxygen Demand and Supply:

  • Lowered cardiac output leads to peripheral vasodilation.
  • Increased afterload increases oxygen consumption.

Clinical Manifestations

• Symptoms:
  • Angina (chest pain)
  • Syncope (fainting)
  • Dyspnea (shortness of breath)
• Signs:
  • Pulsus tardus et parvus: Slow, weak pulse.
  • Sudden death due to arrhythmia.

Pathophysiological Concepts

• Hypertrophy: Left ventricular hypertrophy due to increased afterload.
• Increased End-Diastolic Pressure: Leads to potential atrial fibrillation.
• Atrial Fibrillation: Loss of atrial kick, reducing cardiac output.
• Low Pulse Pressure: Systolic and diastolic pressures close together.
• S4 Heart Sound: Due to stiff ventricle, heard as atrial contraction.
• Crescendo-Decrescendo Murmur: Heard best at second right intercostal space.

Diagnostics

• Murmur Changes: Increase/decrease with maneuvers affecting ventricular size and pressure.

Symptom Severity and Prognosis

• Angina: <5 years life expectancy
• Syncope: <3 years
• Heart Failure: <2 years

Treatment Options

• Balloon Valvuloplasty: Temporary relief.
• Surgical Valve Replacement:
  • Bioprosthetic Valve: No anticoagulation needed, lasts <10 years.
  • Mechanical Valve: Requires anticoagulation (warfarin), lasts >10 years.

Special Topics

• Paradoxical Splitting of Second Heart Sound:
  • Causes include aortic stenosis, left bundle branch block, and tricuspid regurgitation.
  • Explained by delayed closure of the aortic valve relative to pulmonic valve.