PHYSIOLOGY

• Coronary Circulation


  Blood supply of the heart

  
• Learning Objectives / Overview

  • Blood supply of the heart
  • Right coronary artery & branches
  • Left coronary artery & branches
  • Anastomoses
  • Lesions
  • Venous drainage of the heart
  • Nerve supply of the heart
  • Clinical Anatomy aspects

  
• Coronary arteries


  Branches of the ascending aorta immediately above the aortic valve that supply the heart

  
• Right coronary artery


  Originates from the right or anterior aortic sinus

  
• Course of the right coronary artery

  1. Between right auricle & infundibulum

  2. Enter atrioventricular groove

  3. At inferior border: turns backwards & to the left

  4. After given off posterior interventricular branch on the diaphragmatic surface, anastomose with terminal part of circumflex branch of Left coronary artery

  
• Branches of the right coronary artery

  • Right marginal artery
  • Posterior interventricular branch
  • Conus branch artery
  • SA nodal artery
  • AV nodal artery

  
• Conus


  Upper front part of the right ventricle
• SA node


  Sinoatrial node
• AV node


  Atrioventricular node
• Branches of the right coronary artery near the beginning

  • Conus branch artery
  • SA nodal artery (in 60% of heart)

  
• Branches of the right coronary artery near the inferior border

  • Right marginal artery

  
• Branches of the right coronary artery on diaphragmatic surface

  • Posterior interventricular branch
  • AV nodal artery (90% of heart)

  
• Distribution of the right coronary artery

  • Both atria & inter-atrial septum
  • SA node (60%) & AV node (90%) and bundle of His
  • Right ventricle except for a narrow strip along the anterior inter-ventricular groove
  • Posterior 1/2 of inter-ventricular septum
  • A narrow strip of left ventricle along the posterior inter-ventricular groove

  
• Disorders of right coronary artery

  May cause sinus bradycardia and AV nodal block

  
• Left coronary artery


  Originates from the left posterior aortic sinus

  
• Course of the left coronary artery

  1. Runs behind pulmonary trunk

  2. Appears between infundibulum & Left auricle

  
• Termination of the left coronary artery

  After a short course (<2.5cm) it divides into Circumflex branch and Anterior interventricular artery (Left Anterior Descending artery)
• Branches of the left coronary artery

  • Anterior interventricular artery
  • Circumflex artery
  • Conus branch artery
  • Left marginal artery
  • Diagonal artery

  
• Course of the circumflex branch of the left coronary artery


  1. Turns round left margin of heart

  2. Runs to the right in the posterior left AV groove

  3. Anastomose with termination of right coronary

  
• Branches of the circumflex branch

  • To left atrium & left ventricle
  • Left marginal artery (left border of heart)

  
• Anterior interventricular branch of left coronary artery


  Also known as Left Anterior Descending artery (LADA)

  
• Course of the anterior interventricular branch (LADA)


  1. Runs down in interventricular groove towards apex

  2. Anastomose with termination of posterior interventricular artery

  
• Branches of the anterior interventricular branch (LADA)

  • Conus branch that anastomoses with its counterpart of right coronary artery
  • Diagonal artery

  
• Distribution of the left coronary artery

  • Left atrium (upper part)
  • Left ventricle except for a narrow strip along posterior inter-ventricular groove
  • Anterior 1/2 of interventricular septum
  • A narrow strip of right ventricle along the anterior inter-ventricular groove
  • SA node (40 %) and AV node (10%)

  
• Arterial supply of the heart (summary)

  • Right coronary artery supplies: RA, part of LA, RV, posterior 1/2 of interventricular septum, part of LV close to posterior interventricular groove

  Left coronary artery supplies: LA, LV except narrow strip along posterior interventricular groove, anterior 1/2 of interventricular septum, narrow strip of RV along anterior interventricular groove

  
• Anastomoses of coronary arteries

  • Between termination of right coronary artery & circumflex artery
  • Between posterior & anterior interventricular arteries
  • Between right & left conal branches
  • Anatomical end arteries

  
• Angina pectoris


  Chest pain of cardiac origin due to inadequate blood supply to heart musculature
• Myocardial infarction


  Sudden blockage of a large coronary artery or its main branches results in ischaemia of heart with pain of a severe nature
• Venous drainage of the heart


  Most blood drains into the coronary sinus, remainder returned to right atrium by anterior cardiac veins

  
• Coronary sinus


  Continuation of great cardiac vein, in the posterior part of atrioventricular groove, empties into the right atrium

  
• Veins draining into the coronary sinus

  • Great cardiac vein
  • Middle cardiac vein
  • Small cardiac vein
  • Oblique vein of left atrium
  • Posterior veins of left ventricle

  
• Cardiac plexuses


  Around ligamentum arteriosum

  
• Nerve supply of the heart

  • Sympathetic: Cardiac branches from cervical & upper 4 or 5 thoracic ganglia supply SA node, AV node, cardiac muscle & coronary arteries

  Parasympathetic: Vagus nerve synapses at cardiac plexuses, supplies SA node, AV node & coronary arteries

  
• Cardiac pain


  Afferent pain fibres from heart carried by cardiac branches of sympathetic trunk, enter spinal cord by posterior roots of T1-T4 thoracic nerves
• Referred pain from heart

  Central nervous system perceives pain from the heart as coming from the somatic portion of the body supplied by the thoracic spinal cord segments
• Areas of referred pain from the heart

  • Chest wall via upper 4 intercostal nerves
  • Medial side of left arm via T2 (intercostobrachial nerve)
  • Epigastrium from inferior or diaphragmatic surface of heart via T7, T8 & T9 spinal nerves
  • Neck & jaw - spread of nervous information within central nervous system