Origin and Course
The left coronary artery originates from the aorta at the level of the left aortic sinus (sinus aortae sinister).
From its origin, the vessel courses to the left. It passes posterior to the root of the pulmonary trunk (truncus pulmonalis), lying between it and the left auricle (auricula sinistra). Upon reaching the left part of the coronary sulcus (sulcus coronarius), the main trunk divides into its terminal branches.
Branches of the Left Coronary Artery
The left coronary artery divides into two primary branches:
- Anterior interventricular branch (r. interventricularis anterior / LAD) — the continuation of the main trunk. It descends in the anterior interventricular sulcus, wraps around the apex of the heart, and terminates near the posterior interventricular sulcus. Before reaching the posterior interventricular branch, it penetrates the myocardium. It gives off septal interventricular branches (rr. interventriculares septales), the conus branch (r. coni arteriosi), branches to the anterior part of the interventricular septum, the diagonal lateral branch (r. lateralis) supplying the anterior wall of the left ventricle, and anastomotic branches with the right coronary artery. It provides the main blood supply to the apex of the heart.
- Circumflex branch (r. circumflexus) — emerges from beneath the left auricle, runs within the coronary sulcus to the pulmonary (left) surface, and then extends onto the diaphragmatic surface. As it transitions to the diaphragmatic surface, it gives off a prominent posterior branch of the left ventricle (r. posterior ventriculi sinistri) supplying the anterior and posterior walls of the left ventricle. The left marginal branch (r. marginalis sinister) descends inferiorly and posteriorly along the pulmonary surface toward the apex.
Lymphatic Drainage Along the Artery
Cardiac lymphatic vessels are divided into deep and superficial networks. Deep vessels originate from the myocardium and endocardium, while superficial vessels begin in the epicardial capillary networks.
Drainage pathways accompany the coronary arteries. The left pathway travels along the a. coronaria sinistra: these lymphatic vessels converge, ascend along the posterior wall of the pulmonary trunk, and drain into the tracheobronchial nodes near the tracheal bifurcation.
Clinical Significance
Coronary arteries are critical for understanding the topical diagnosis of myocardial infarction (MI).
Common abbreviations in clinical practice:
- LCA — left coronary artery;
- LAD — left anterior descending artery;
- Cx — circumflex artery;
- MI — myocardial infarction;
- NSTEMI — non-ST-segment elevation myocardial infarction.
In stable ischemic heart disease (IHD), revascularization strategies are chosen between CABG (coronary artery bypass grafting) and PCI (percutaneous coronary intervention).