Coronary Circulation & Arteries

Coronary Arteries

• Cardiac muscles receive their blood supply from two coronary arteries: the right coronary artery (RCA) and the left coronary artery (LCA).
• Both the RCA and LCA originate from the coronary sinuses, located just superior to the aortic valve cusps at the aortic root.
• The coronary arteries are responsible for delivering oxygenated blood to the cardiac muscle.

Aortic Valve

• The aortic valve consists of three cusps: the left coronary (LC) cusp, the right coronary (RC) cusp, and the posterior non-coronary (NC) cusp.
• The right coronary cusp gives rise to the right coronary artery
• The left coronary cusp gives rise to the left coronary artery.

Right Coronary Artery (RCA)

• The right coronary artery is located in the right atrioventricular groove, and its posterior interventricular branch is in the posterior interventricular groove.
• Branches of the right coronary artery include the SA nodal artery (60%) which supplies the sinuatrial node and surrounding myocardium.
• The right marginal artery supplies the right ventricle.
• In 67% of the population the posterior IV artery supplies the RV, LV, IV septum.
• The AV nodal artery supplies the atrioventricular node, surrounding myocardium.

Left Coronary Artery (LCA)

• The left coronary artery is in the left atrioventricular groove, and its anterior interventricular branch is located in the anterior interventricular groove.
• Branches of the left coronary artery are the circumflex artery supplies the posterior surface of the LV.
• The anterior IV artery supplies to the RV, LV, IV septum.
• In 40% of the population the SA nodal artery supplies the sinuatrial node, surrounding myocardium.
• The left marginal artery supplies to the left ventricle
• In 33% of the population the posterior interventricular artery supplies the right and left ventricles.

Areas Supplied by Coronary Arteries

• The Left Circumflex Artery supplies the left atrium and left ventricles.
• The Left Anterior Descending Artery supplies the right ventricles, left ventricles, and interventricular septum.
• The Left Marginal Artery supplies the left ventricles.
• The Right Coronary Artery supplies the right atrium and right ventricles.
• The Right Marginal Artery supplies the right ventricles and the apex.
• The Posterior Interventricular Artery supplies the right and left ventricles and interventricular septum.

Coronary Arteries

• Left coronary artery branches into to the Left anterior ascending (LAD), the Left marginal artery (LMA), and the circumflex artery (CX).
• Right coronary artery branches into to the Right marginal artery (RMA) and the Posterior descending artery (posterior interventricular artery) (Plv).

Coronary Dominance

• Coronary dominance is determined based on the vessel that gives rise to the posterior descending artery, which supplies the Atrio-ventricular node.
• Coronary dominance is recognized by the presence of septal perforating branches.
• In 80% of the population dominance arises from the RCA, and from the LCX in 10% of the population.
• About 10% of the population has Co-Dominance where the posterior interventricular artery is formed by both the RCA and LCx.
• In right dominance, the posterior interventricular artery is a branch of Right coronary artery.
• In left dominance, the posterior interventricular artery is a branch of Left coronary artery.

Venous Drainage

• Veins include the great, middle, small, and posterior cardiac veins which drain to the coronary sinus which drains to the right atrium.
• The anterior cardiac vein drains to right atrium.
• The venae cordis minimae drain to near chamber

Coronary Sinus

• The great cardiac vein begins at the apex of the heart and ascends in the anterior interventricular sulcus and is named, the anterior interventricular vein.
• In the coronary sulcus, the great cardiac vein gradually enlarges to form the coronary sinus and enters the right atrium.
• The termination ends in the right atrium.
• The opening is guarded by the valve of the coronary sinus.
• The coronary sinus receives the middle cardiac vein and small cardiac veins at its right end.
• The left posterior ventricular vein and the oblique vein of the left atrium (of Marshall) open into the coronary sinus.

Myocardial Infarction (MI)

• Myocardial Infarction (MI) is a sudden occlusion of a major artery by an embolus.
• When occlusion occurs, the region of myocardium supplied by the occluded vessel becomes infarcted and undergoes necrosis.
• Three most common sites of coronary artery occlusion: Anterior IV (LAD) branch of the LCA (40-50%), RCA (30-40%), and circumflex branch of the LCA (15-20%).

Ischemic Heart Disease (IHD)

• The most common cause of ischemic heart disease is coronary artery insufficiency resulting from atherosclerosis.
• Percutaneous Transluminal Coronary Angioplasty (PTCA) is a surgical procedure.
  • "Percutaneous" refers to through the skin.
  • "Transluminal" refers to within the lumen or artery.
  • "Coronary" refers to the artery supplying the heart muscle.
  • "Angioplasty" refers to remodeling the artery.

Conduction System

• The Sinoatrial (SA) node generates impulses around 75 times per minute.
• The Atrioventricular (AV) node delays the impulse about 0.1 second.
• Impulses pass from the atria to the ventricles via the atrioventricular bundle of His.
• Then, the AV bundle splits into two pathways inside the interventricular septum called the bundle branches.
• The right and left bundle branches carry the impulse toward the apex of the heart.
• The purkinje fibers carry the impulse to the heart apex and ventricular walls.

Autonomics

• Sympathetics originate from the Off chain T1-4
• Parasympathetics originate from the Vagus CN X
• Cardiac and pulmonary nerve plexuses are formed.
• Sympathetics increase heart rate, dilate cardiac vessels
• Parasympathetics decrease heart rate and constrict cardiac vessels.