Left Coronary Artery

Origin

The coronary arteries are the first branches of the thoracic aorta and the only branches of the ascending aorta, arising from its proximal portion below the sinutubular junction.

The left coronary artery arises from the left coronary aortic sinus. It is larger in diameter than the right coronary artery, since it provides vascular supply to a greater portion of the myocardium and epicardium. Occasionally, there is a double origin, and this corresponds to the two main branches of the left coronary artery, namely the circumflex and the anterior interventricular arteries.

The arteries are subepicardial but may be more deeply embedded in regions such as the interventricular grooves. In addition, they are covered by adipose tissue and may be somewhat hidden on initial inspection of the heart during cadaveric dissection.

Course

The left coronary artery sits between the pulmonary trunk and the left atrial appendage. It courses towards the atrioventricular groove en route to the left cardiac border. This portion does not typically have any branches; however, a small atrial branch may arise and on a rare occasion it may give off the sinuatrial nodal artery (Standring, 2016).

Within the atrioventricular groove, the left coronary artery bifurcates into the circumflex and anterior interventricular arteries. The distance between its origin and its first branch is variable.

Branches

There are two main branches of the left coronary artery, the circumflex and anterior interventricular branches. The circumflex branch travels within the coronary sulcus from the anterior aspect to the posterior aspect of the heart. The anterior interventricular branch is often considered a continuation of the left coronary artery. It descends within the anterior interventricular sulcus (Standring, 2016).

Variations in the branching pattern of the coronary arteries exist, where the posterior interventricular branch may arise from the left coronary artery (33% of individuals) (Moore, Dalley and Agur, 2013).

Supplied Structures

The left coronary artery supplies the majority of the left ventricle, a narrow portion of the right ventricle, the anterior two-thirds of the interventricular septum, and the majority of the left atrium.

The arterial supply to the diaphragmatic surface of the heart is the most variable in terms of right or left coronary arterial supply. Its supply is related to which vessel is dominant. The term dominant does not refer to the amount of cardiac tissue supplied by the arteries, but from which coronary artery that gives rise to the inferior interventricular artery (aka the posterior descending artery [PDA] or posterior interventricular artery). This artery supplies the diaphragmatic inferolateral wall of the left ventricle. The right coronary artery is dominant in 67% of individuals (Moore, Dalley and Agur, 2013).

List of Clinical Correlates

- Coronary artery disease

- Coronary atherosclerosis

- Coronary bypass graft

- Coronary angioplasty

- Coronary occlusion

- Coronary revascularization

- Coronary artery fistula

References

Moore, K. L., Dalley, A. F. and Agur, A. M. R. (2013) Clinically Oriented Anatomy. Clinically Oriented Anatomy 7th edn.: Wolters Kluwer Health/Lippincott Williams & Wilkins.

Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41st edn.: Elsevier Limited.