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Left Main Coronary Artery (LMCA)

A Cath Lab Anatomy & Hemodynamics term on the RCIS exam blueprint, defined for cath lab and EP clinicians.

Originates from the left coronary sinus and bifurcates into the Left Anterior Descending (LAD) and Left Circumflex (LCX) arteries. In some individuals, a third branch—the ramus intermedius—arises at this junction.

Anterior view of the heart with the left main coronary artery highlighted on the image’s left, at its origin from the left coronary sinus, bifurcating into the left anterior descending and left circumflex arteries, with a ramus intermedius shown as a variant third branch present in some individuals.
The left main and its bifurcation, with the ramus intermedius variant.

Domain: Cath Lab Anatomy & Hemodynamics · Blueprint: RCIS exam guide

Related RCIS terms

Atrioventricular (AV) Node Bundle Branches Left Anterior Descending (LAD) Artery Left Circumflex (LCX) Artery Posterior Descending Artery (PDA)

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Written and reviewed by John-Philip (JP) Maarschalk, BSN, RN, CNML — a nurse manager who runs operations for the cardiac cath lab, electrophysiology, and interventional service lines at an academic health system in North Carolina. He hires and develops the staff who sit for these exams. More about JP and how this content is made →
Cardiac Codex is an independent study tool published by MdoubleA LLC, not affiliated with or endorsed by CCI or any certifying body. This glossary entry is exam-preparation information, not medical advice or a substitute for clinical judgment. Always verify current clinical practice against primary sources and institutional protocol.