Left coronary artery
Arteria coronaria sinistra
Also known as: left main coronary artery, LMCA, left main stem
The left coronary artery arises from the left aortic sinus as a short left main stem. It passes between the pulmonary trunk and the left auricle and then divides into the LAD and circumflex arteries, which together supply most of the left ventricle, the left atrium and the anterior two-thirds of the septum.
Overview
The left main stem is usually only 1–2.5 cm long. It runs to the left behind the pulmonary trunk and then forward between the pulmonary trunk and the left auricle. On reaching the AV groove it divides into the left anterior descending (anterior interventricular) artery and the circumflex artery. In a significant minority of hearts it trifurcates instead, giving a third branch, the ramus intermedius, which supplies the anterolateral wall.
The left coronary system usually perfuses more than half of the left ventricular myocardium. For this reason, significant stenosis of the left main stem is a high-risk lesion and is a classic indication for revascularisation.
Anatomy
- Course
It starts in the left aortic sinus, runs behind and then to the left of the pulmonary trunk, and emerges between the trunk and the left auricle. It divides at the left end of the coronary sulcus.
- Branches
The left anterior descending artery, the circumflex artery and sometimes a ramus intermedius.
Function
- Supplies the anterior and lateral left ventricle, the apex, the left atrium and the anterior two-thirds of the interventricular septum.
- Through the LAD's septal perforators, supplies the bundle of His and bundle branches.
- Supplies the SA node in about 40% of people (via the circumflex).
Clinical significance
Left main disease
Occlusion of the left main stem jeopardises most of the left ventricle and is often fatal. On the ECG, ST elevation in aVR together with widespread ST depression suggests left main or multivessel ischaemia. Significant left main stenosis is treated with CABG or with complex PCI.
Anomalous left coronary artery
In ALCAPA (Bland–White–Garland syndrome), the left coronary artery arises from the pulmonary artery instead of the aorta and causes infant ischaemia and heart failure. Separately, a coronary artery that runs between the aorta and the pulmonary trunk (an interarterial course) can cause sudden death in young athletes.
Compiled from standard anatomy and physiology references — see the Cardiovascular System sources. For education only; not medical advice.