Objectives:

This angle is usually taken as the first image in the series. Engaging the left coronary system usually occurs in AP, however the catheter seen in the distal aorta usually overlaps the left main artery, possibly obscuring a narrowing. As soon as the catheter is engaged, the radiographer (or whoever is moving the detector) should immediately angle RAO to clear the left main of the distal catheter. This is usually 10 degrees however can sometimes be as much as 20 degrees. If necessary, consult your cardiologist for initial projections greater than 15 degrees.

This projection is good for a quick assessment of the left main artery, however can be slightly foreshortened and overlapped by the proximal circumflex. It is good for the mid circumflex and obtuse marginal branch. The proximal circumflex is difficult to visualise due to foreshortening, as it is seen end on as it bifurcates from the left main artery. The LAD is difficult to visualise due to overlapping by the diagonal branches.

Catheter Positioning:

Ensure the catheter is located in the top left corner of the screen.

Alternatives:

More RAO (eg. RAO 30):

Left main becomes completely overlapped by the circumflex. The LAD is perpendicular the detector in this view however is often overlapped along its length by diagonals and septals

Less RAO (eg. AP):

Demonstrates the proximal left main free from overlap however suffers from foreshortening. This view is good for demonstrating the mid / distal circumflex. The proximal LAD and circumflex are overlapped, with the obtuse marginal often overlapping the mid / distal LAD. Beware that the catheter seen in the descending aorta often obscures the left main / proximal LAD.

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