Anatomy Relevant to Acute Coronary Artery Disease

by Adam Lawson BA, MSc and Terra Doucette Hiller BA, BSN, RN

Coronary Arteries

Coronary arteries supply the heart with oxygen and nutrients. The vessels arise from the aorta directly above the aortic valve.

Coronary arteries initially supply the epicardial layer of the heart; smaller arteries branch off the coronary arteries at 90° to supply the deeper endocardial layer.

Right coronary artery - supplies the:
- Right atrium
- Right ventricle
- Sinoatrial node (~55% cases)
- Atrioventricular bundle (~90% cases)
- Posterior portion of the left ventricle
  
  Rotate to 180° to view the coronary supply of the posterior left ventricle. Rotate back to 0° when you are finished.
Left coronary artery
- Left anterior descending artery- supplies the:
  - Anterior two thirds of the intraventricular septum
  - Anterior left ventricle
  - Lateral left ventricle
  - Bundle branches
- Left circumflex artery - supplies the:
  - Left atrium
  - Posterior left ventricle
  - SA node (~45% cases)
  - AV node (~10% cases)
  If you cannot locate the SA or AV node, click on the link and zoom in to a scale of about 2.3x

Walls of the Heart

The heart is generally said to have four distinctive walls corresponding to the shape of its surface. The walls are supplied by different branches from the coronary arteries and can be monitored by specific groups of leads during EKG.

Anterior wall ("sternocostal surface") - receives blood supply from the:
- Left anterior descending coronary artery.
Leads V3 and V4 in a 12-lead EKG interpret the electrical activity of the anterior wall.
Inferior wall ("diaphragmatic surface") - receives blood supply from the:
- Right coronary artery
- Left circumflex artery
Leads II, III and aVF in a 12-lead EKG interpret the electrical activity of the inferior wall.
Posterior wall ("vertebral surface") - receives blood supply from the:
- Right coronary artery
- Left circumflex artery
To interpret the electrical activity of the posterior portion of the heart, one must normally perform a EKG on the back. Lead placement of the posterior EKG positions correspond to those of a normal anterior EKG, only difference are the leads are place on the individuals back.
Lateral wall ("left surface") - receives blood supply from the:
Leads I, aVL, V5 and V6 of a 12-lead EKG interpret the electrical activity of the lateral wall.

Vessels used in Coronary Artery Bypass Surgery

Saphenous vein graft

The long length of the saphenous veins gives no anatomical limitation to allowance of multiple graft sites, but it often does not have as long-term patency as that of arterial grafts due to its non-arterial structure.
Internal mammary artery

The internal mammary artery (IMA) remains attached to its origin, but it is reattached distal to the block in the coronary artery. The grafted IMA has been shown to remain patent longer than the saphenous vein assumedly because of its appropriately arterial structure. The shorter length of the IMA suits it for use with proximal blocks in the coronary arteries requiring shorter grafts.
Right gastroepiploic artery

The right gastroepiploic artery (GEA) is harvested from the pericardial cavity and anastomosed (i.e., connected) to a distal portion of the coronary artery. Patency of the artery has had an excellent review despite being smaller than the internal mammary artery. The GEA has been used for bypassing the right coronary artery, the circumflex artery or the posterior descending artery.

Coronary Veins

Coronary veins drain most of the blood from the myocardium into the coronary sinus before it reaches the right atrium. The Thebesian valve controls blood flow from the coronary sinus into the right atrium.

Anterior cardiac veins - drain blood from the:
- Right atrium
- Right ventricle
The anterior cardiac veins include the left marginal vein and two to three other smaller vessels.

Unlike other cardiac veins, anterior cardiac veins do not drain into the coronary sinus; instead, blood drains directly into the right atrium.
Great cardiac vein (a.k.a., left coronary vein) - drains blood from the:
The great cardiac vein collects blood from the left marginal vein which runs along the left ventricle.
Posterior veins of the left ventricle - drain blood from the left ventricle.

The posterior veins of the left ventricle run along the diaphragmatic surface of the left ventricle. Although these veins typically drain into the coronary sinus (as is the case with this specimen), they are sometimes found to drain into the great cardiac vein.
Posterior intraventricular veins (a.k.a., middle cardiac vein) - drain blood from the:
- Left ventricle
- Right ventricle

References