During CABG arterial grafts are always preferred over venous grafts , for the simple reason the grafted vessel has to carry arterial blood and not the venous blood. Saphenous veins are tuned to carry venous blood at low pressure.The mean coronary arterial pressure is around 40mmhg and this will damage the saphenous venous endothelium more quickly. The reocculsion rate at 10 years for venous grafts can reach 60%.
Left internal mammary artery (LIMA) is the most commonly used arterial graft. This is usually anastamosed with LAD. The lumen of LAD & LIMA are more or less equal and they match well in character also !
The other advantage of LIMA graft is , blood tends to flow both during systole and diastole in a smooth fashion.. Since the venous graft which hangs from the root of aorta , the ostium of venous graft lacks the hemodynamic benefits of coronary sinus . (We know the coroanry sinus acts like a reservoir for the smooth release of blood flow into coronary arteries.)
Finally , the most important feature of LIMA is
It is a live graft
LIMA’s proximal origin from subclavian is left intact, so LIMA acts as a live vessel with it’s vasa vasorum intact , which means the endothlium derived relaxing factor (EDRF-Nitric oxide) secretion is not interrupted.This makes the LIMA an excellent graft , self protected against reocclusion.One may call it a drug eluting graft !
What is the patency rate for LIMA ?
LIMA patency rates at 10 years is nearly 90 % .But the graft patency depends on many factors , like diabetes, age, gender, surgical technique ,(Now , beating heart CABG is very popular , where the LIMA patency is said to be slightly lower than conventional CABG) Sequential LIMA grafts, free LIMA graft ( Which loses the advantage of being a live graft) have relatively lower patency rates.
What are the other arteries used in CABG ?
Other arteries that could be used are radial artery, right internal mammary artery, and gastro epiploic artery.The patency rates of all these arteries far less than LIMA .