CathLabViewer
CathLabViewer· Cardiac Imaging Guide

Anatomy

Left coronary artery

The left main coronary artery (LMCA) arises from the left coronary cusp of the aortic root. After a short trunk it bifurcates — sometimes trifurcates — into the left anterior descending (LAD) and left circumflex (LCx). A ramus intermedius may emerge between them.

Segments

Click a segment to highlight it in the viewer and pull up its profile.

Picking a view

  • Spider (LAO 40 / CAU 30): always start here for the left main bifurcation.
  • RAO 30 / CAU 30: rolls out the LCx and obtuse marginals along the AV groove.
  • RAO 10 / CRA 40: opens the mid and distal LAD with diagonals separated.
  • LAO 30 / CRA 30: isolates the proximal LAD and its diagonal take-offs from the LCx.
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Click a vessel segment to inspect it

Left coronary views

Why this view: Orientation view. Detector directly anterior. Useful for catheter engagement and quick anatomy overview.

No segment selected

Click any left coronary vessel segment in the viewer to see what it supplies and the best fluoroscopy views to image it.

Further anatomy

Branches not visualised in the model

Septal perforators (S1, S2…)

A series of branches that arise at near-right angles from the LAD and dive deep into the interventricular septum, supplying its anterior two-thirds. They also carry blood to the bundle branches of the conducting system — which is why LAD occlusion proximal to the first septal can cause bundle branch block, and why the LAD is sometimes called "the artery of sudden death." The septal perforators aren't usually individually stented but their relationship to a lesion matters enormously during PCI planning.

Ramus intermedius

When the LMCA trifurcates, the ramus intermedius emerges between the LAD and LCx, running diagonally across the lateral wall. It effectively acts as a large first diagonal or a large first obtuse marginal, depending on its course. Present in roughly 20–30% of patients — worth recognising so it isn't misread as a bifurcation lesion on the spider view.