Normal Cardiac Cycle

Normal Heart Sounds

• S1
• S2

Normal Cardiac Conduction

Cardiac Conduction System

Electrical Correlates of the Normal EKG (see Electrocardiogram)

• PR Interval
  • Depolarization of Atrium (P-Wave)
  • Conduction Through AV Node
  • Conduction Through His Bundle
  • Conduction Through Bundle Branches
  • Conduction Through Fascicles
  • Conduction Through Terminal Purkinje Fibers
• QRS
  • Ventricular Depolarization
• T-Wave
  • Ventricular Repolarization

Blood Supply to the Cardiac Conduction System

• Blood Supply to the Sinoatrial (SA) Node
  • Right Coronary Artery: 60% of patients
  • Left Circumflex Artery: 40% of patients
• Blood Supply to the Atrioventricular (AV) Node
  • Right Coronary Artery: 90% of patients
  • Left Circumflex Artery: 10% of patients
• Blood Supply to the His Bundle
  • Right Coronary Artery: main blood supply
  • Septal Perforators of the Left Anterior Descending Coronary Artery: minor contribution
• Main/Proximal Left Bundle Branch
  • Left Anterior Descending Artery: main blood supply
  • Right Coronary Artery: collateral flow
  • Left Circumflex Artery: collateral flow
• Left Anterior Fascicle
  • Septal Perforators of the Left Anterior Descending Coronary Artery: main blood supply
  • AV Nodal Artery: 50% of patients
• Left Posterior Fascicle
  • Proximal Left Posterior Fascicle
    • AV Nodal Artery: main blood supply
    • Septal Perforators of the Left Anterior Descending Coronary Artery: in some cases
  • Distal Left Posterior Fascicle
    • Anterior and Posterior Septal Perforating Arteries (Dual Blood Supply)
• Right Bundle Branch
  • Septal Perforators of the Left Anterior Descending Artery: main blood supply
  • Right Coronary Artery: some collateral flow (depending on dominance of the system)
  • Left Circumflex Artery: some collateral flow (depending on dominance of the system)

References

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