Heart Anatomy and Atrial Fibrillation

Jul 12, 2024

Heart Anatomy and Atrial Fibrillation

Heart Chambers

  • Four Chambers:
    • Upper: Right and Left Atrium
    • Lower: Right and Left Ventricles

Fibrillation

  • Definition: Muscle fibers contracting at different times causing quivering or twitching.

Normal Electrical Signal Propagation

  • Originates in the sinus node (right atrium)
  • Fast propagation through both atria
  • Coordinated atrial contraction
  • Signal moves to ventricles causing contraction

Atrial Fibrillation (AF or A-fib)

  • Nature:
    • Disorganized signals in the atria overriding sinus node
    • Atria appear to quiver instead of contracting

ECG During AF

  • Normal ECG:
    • P wave (atrial contraction) followed by QRS complex (ventricular contraction)
  • AF ECG:
    • Scribble-like pattern, irregular QRS complexes
    • Heart rate: 100-175 bpm

Impact of AF

  • Loss of atrial kick (not life-threatening)

Causes and Risk Factors for AF

  • Cardiovascular Diseases:
    • High blood pressure, coronary artery disease, valvular diseases
  • Other Risk Factors:
    • Obesity, Diabetes, Excessive alcohol consumption
  • Genetic Component

Mechanisms

  • Tissue Heterogeneity: Causing unpredictable conduction
  • Multiple Wavelet Theory: Multiple wavelets conducting randomly
  • Automatic Focus Theory: Rapid firing of electrical impulses from specific origins (e.g., cardiac muscle around pulmonary veins)

AF Progression

  • Paroxysmal Events:
    • AF comes and goes, lasting less than a week
    • Repeated events stress atrial cells
  • Persistent AF: Longer than a week without self-terminating
  • Long-Standing Persistent AF: Lasts beyond 12 months
  • Permanent AF: Decision to not attempt rhythm correction

Symptoms

  • Common Symptoms:
    • General fatigue, dizziness, shortness of breath, weakness, palpitations or thumping in chest

Complications

  • Stroke:
    • Blood clots forming in the atria can travel to the brain causing stroke

Diagnosis

  • Methods:
    • ECG for persistent AF
    • Holter Monitor for recording paroxysmal events

Treatment

  • Medications:
    • Control heart rate, reduce blood clots
  • Implantable Devices:
    • Cardiac pacemaker
  • Surgical Interventions:
    • Radiofrequency catheter ablation, Maze procedure, Ablation of AV node combined with pacemaker implantation