Ramus Intermedius

ramus intermedius coronarius

The ramus intermedius (intermediate branch) is a coronary artery variant present in approximately 20-37% of individuals, arising from the left main coronary artery between the left anterior descending (LAD) and the left circumflex (LCx). It supplies the lateral left ventricular wall in the territory normally covered by the first diagonal branch of the LAD or the first obtuse marginal branch of the LCx.

Region: Chest

Clinical Relevance

Clinical Notes

The ramus intermedius is clinically significant because its occlusion produces a lateral myocardial infarction that may be attributed incorrectly to the LAD or LCx territory. On the standard ECG, ramus occlusion produces lateral wall changes (I, aVL leads). In coronary CT angiography and catheterisation, identification of the ramus intermedius changes the anatomical description from a two-vessel to a three-vessel left coronary system. Bypass surgery planning must account for the ramus as a separate graft target.

Pathology

Common Injuries & Conditions

Ramus Intermedius Occlusion Producing Lateral MI

Acute occlusion of the ramus intermedius produces lateral wall myocardial infarction with ST changes in leads I and aVL on ECG, resembling a circumflex territory event; coronary angiography identifies the ramus as a distinct vessel requiring primary PCI or bypass grafting separate from the LAD and LCx.