Ramus intermedius is referred to as RI. The trifurcation of the main coronary artery on the left results in the formation of the ramus intermedius, a variant coronary artery. In 20% (range 10-30%) of the population, it is present. It can follow a similar path to the diagonal branching of the left anterior descending artery or the obtuse peripheral branches of the left circumflex artery, and can thus serve the anterior and/or medial aspect of the heart. This vessel is unusual in that it glides across the left ventricle’s free surface rather than following an anatomical groove.
Since there is an opposite relationship between the circumference of the ramus intermedius artery and the size as well as distribution of the various diagonal branches, some cardiologists may refer to an influential early branching obtuse marginal artery as a ramus branch in practise even though there is not any true trifurcation. The ramus intermedius is the name for the artery that emerges from the main coronary artery in the left between the anterior descending artery on the left and the left circumflex artery. The ramus intermedius is a normal variation that affects 37 percent of the general population. The left major bifurcation angle gives rise to the variant vessel known as the ramus intermedius.