The video below uses a heart model to narrate a description of how the major coronary arteries travel over the surface of the heart. The Tabs on the left provide additional details about each artery.
The LAD or left anterior descending coronary artery travels in the anterior inter-ventricular groove that runs between the right and the left ventricles (RV and LV) or the two lower chambers of the heart. The LAD gives rise to the following two sets of branches:
- The diagonals (Dx) are branches of the LAD that runs diagonally away from the LAD and towards the left front left side of the heart. The Dx branches are named according to the order of origin. The very first one is called the 1st Dx or Dx1, the second is Dx2, and so on.
- The septal perforators (SP) runs into the septum (partition that separates the two ventricles) and provides its blood supply. They are also named according to the level of origin, i.e., 1st major septal perforator, etc.
The LAD is divided into three segments or parts. The proximal LAD is the portion before the origin of the first Dx branch, while the segment just below the Dx is the mid LAD. The distal segment of the LAD is the terminal third of the artery.
Blockage of the LAD results in decreased blood supply to the anterior or front portion of the heart. A heart attack involving the LAD is known as an anterior wall myocardial infarction or MI. A blockage occurring near the beginning of the LAD causes a larger heart attack (involving more muscle) than one occurring downstream or nearer the end portion of the artery.
Total blockage of the Dx branch can cause a heart attack involving the anterolateral-lateral (anterior = front and lateral = outer side) portion of the LV while blockage of the SP causes damage to the partition (septum) of the ventricle. An anterolateral and septal MI can occur together with an anterior wall MI when the LAD blockage is prior to the origin of these branches. One can also have an isolated anterolateral or septal MI when the blockage involves one of these branches and spares the LAD.
The Circumflex (Circ) coronary artery is a branch of the left main coronary artery. It travels in the left atrio-ventricular groove that separates the left atrium (left upper chamber) from the left ventricle. The Cx moves away from the LAD and wraps around to the back of the heart. The major branches that it gives off in the proximal or initial portion are known as obtuse (pronounced Ob-tews) marginal or OM coronary arteries. As it makes its way to the back or posterior portion of the heart, it gives off one or more left postero-lateral artery (LPLA) branches.
In 85% of cases, the Cx terminates or ends after it gives off the LPLA branches and is known as a non-dominant left coronary artery system.
In the other 15% of cases, a dominant Cx supplies the PDA or posterior descending artery that lays in the bottom of the heart within a groove that separates the left from the right ventricle.
An example of a dominant right coronary artery is shown on the top left diagram while a dominant left coronary artery or dominant Cx system is shown in th the lower diagram.
A heart attack involving blockage of the Cx coronary artery usually causes damage to the back or posterior portion of the left ventricle and is known as a posterior wall myocardial infarction or posterior MI.
If the arterial blockage occurs near the beginning or proximal portion of the Cx, a larger amount of muscle is involved. If it compromises flow to the OM and the LPLA branches, the outer back side or posterolateral portion of the heart (that gets blood flow from these branches) gets jeopardized. This is known as a posterolateral MI.
In cases of a dominant left coronary artery, a proximal Cx blockage can create a posterior, posterolateral AND an inferior MIsince it also cuts off flow to the bottom or inferior portion of the heart that is supplied by the LPDA (or left posterior descending coronary artery) in such cases.
A posterior-lateral MI (without an associated posterior MI) can occur if the OM and LPLA branches are blocked after their origin from the Cx. Similarly, an isolated inferior wall MI can also occur if the LPDA is blocked after it originates from the dominant Cx. Also, see the Right coronary artery (RCA section) for additional causes of an inferior wall MI.
The right coronary artery or RCA usually originates above the right portion of the aortic valve (that is known as the RC or right coronary cusp). Remember that the left coronary artery originates from the LC or left coronary artery. The third cusp does not generally give rise to a coronary artery and is known as the posterior (because it is located behind the other two cusps) NC or non-coronary cusp. After coming off the aorta, the RCA runs in the groove that separates the right atrium from the right ventricle (right atrio-ventricular or AV groove). It then makes its way to the bottom or inferior portion of the heart. This is also known as the diaphragmatic wall because it sits on top of the diaphragm (the muscle partition that separates the chest from the abdomen.
The acute marginal coronary artery is given off in the proximal or early course of the artery. While the terminal or distal portion of the RCA gives off the right posterior descending artery or RPDA. The RPDA runs in the bottom of the heart in a groove that separates the left and right ventricles This is known as the posterior intraventricular or IV groove. The RPDA supplies branches to the lower most portion of the septum (partition between the two ventricles). In such cases, the RCA is said to be dominant (see top left diagram). In another 15% of cases, RCA is "non-dominant" and stops before it reaches the posterior IV groove. In such cases, the Cx supplies the PDA branch.
The RCA also supplies the postero-lateral artery or PLA to the lower back portion of the left ventricle and the right ventricular branch to the right ventricle.