MadSci Network: Anatomy

Re: What about the vein in coronary by-pass surgery?

Date: Tue Apr 10 11:20:33 2001
Posted By: Joshua Chai, Medical student, Medical Sciences, University of Cambridge
Area of science: Anatomy
ID: 986829298.An

You are absolutely right! The idea about Coronary Artery Bypass Graft (CABG) is to graft a piece of blood vessel, usually from the patient him/herself (hence “autologous”, minimising the possibility of graft rejection), to by-pass a segment of coronary vessel narrowed by atherosclerosis, and therefore re-vascularise the myocardium distal to the narrowing. Previously, people tend to use segments of healthy autologous saphenous vein (a superficial vein in the leg) for bypass, but nowadays people tend to use the internal mammary artery or one of the epigastric arteries for this operation. This is because for some reasons not fully understood, using veins for bypass surgery often results in subsequent complication, i.e. the piece of venous graft often develop thrombosis or further atherosclerosis after the operation, so a second bypass maybe necessary; nevertheless, using the internal mammary artery or one of the epigastric arteries surprisingly results in relatively fewer complication, and hence better survival rate. OK, for your question, our legs have a “dual” venous systems: one deep and one superficial. Both the great and small saphenous veins are of the superficial one. The great saphenous vein runs from the foot, up the medial aspect of the leg to join the femoral vein in the groin whereas the small saphenous vein runs up the back of the calf to communicate with the deep venous system at the back of the knee. So if a segment is removed from one of the saphenous veins for bypass graft, venous circulation can often be compensated by the other superficial veins and the complementary deep venous system. Similarly, most muscles in the body are not supplied by a single end-artery, rather, arterial anastomosis exists so that one muscle receives arterial supply by the branches of a number of arteries each communicating with one another in the capillary-bed level. So that even a arterial segment is removed, blood supply is usually unaffected.

This is not to say that it’s 100% ill-effect free, but comparing the severity and prospect of having angina pectoris (severe chest pain due to myocardial ischaemia) or having an MI (myocardial infarction: death of part of the myocardium due to ischaemia) and some minor circulatory problems in the calf region of one of your leg (people after CABG are often advised not to do strenuous exercise anyway!), I think the benefits far outweigh the ill-effects!

I hope I have answered your question:-)

Joshua Chai
Medical Student
University of Cambridge, UK

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