Coronary arterial circulation is the life line for the human heart and it’s survival.Typically it is supplied by two coronary arteries, left and right coronary artery.Both, together carry about 250ml of blood every minute.( Approxinately equal to a cup of coke ! ).These coronary arteries generally divide in a predetermined fashion , and have multiple branches . It is a mystery , what decides this branching pattern
Is it like a our palmar crease ? or the cerebral gyri ?
However , it does follow a certain rule, one major coronary artery will follow the four important grooves of heart. In the left side , left main coronary artery (LM) originates in the left coronary sinus (Size varying between 1mm -20mm) and usually bifurcates into LAD and LCX. The left anterior descending artery (LAD) runs in anterior interventricular groove while , the right atrio ventriculo groove carries the right coronary artery(RCA) .Left circumflex artery (LCX) traverses the left atrio ventricular groove.The most inconstant branch is the posterior descending artery (PDA) which runs in the posterior interventricular groove.PDA can arise from either RCA, LCX or both or even from LAD.
The major branches of LAD are called diagonal and septal while the branches of LCX are called obtuse marginal(OM).There can be two to three diagonal and OMs.
What is ramus intermedius coronary artery ? What is the incidence of Ramus ?
The left main coronary artery instead of bifurcating into two , it trifurcates into three vessels.(LAD, LCX, Ramus)
The real incidence could vary betweenn (10% to 30%) depending upon the series.
What course it takes ?
It generally goes in the angle between the LAD and the LCX.It may either behave like a large OM or a diagonal branch.It supplies the lateral free wall of the LV many times.The peculiarity of this vessel is it does not run in a anatomical groove .It simply slides over the free surface of LV.Rarely, a very abnormal course of ramus, criss cross the aorta and pulmonary artery .
How common is atherosclerosis within Ramus ?
We don’t know yet. But it is very likely since it is an early branch from left main, it might have a predilection for atherosclerosis as like LAD or LCX ostium.In fact now we recognise more of trifurcation lesions involving three branches of left main .
What would be the ECG finding if a large ramus is the culpirit vessel during STEMI ?
This scenario could be rare.
ACS in ramus could present as ST elevation in 1/Avl /V5,V6
- Lateral MI
- Apical MI
- High lateral MI
But it is realised , whenever the ECG changes are not fitting with typical ASMI or a lateral MI one should suspect a ramus lesion
What is the significance of ramus for an interventional cardiologist ?
PCI in ramus is a rare opportunity for a cardiologist .The issue here is, if ramus is involved adjacent LAD and LCX is also likely to be involved .So it would logically be a multivessel , complex angioplasty.Isolated ramus lesion could be tackled easily.Another issue here could be ,since this vessel is not within any anatomical groove stent deployment would have a poor support and prone for mobilisation and migration .
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Dr.S.Venkatesan MD 