Dear ed34,
Great question. You are absolutely correct that most patients have the option of having coronary angiography performed from either the femoral (leg) or radial (arm) artery access sites. For the femoral site, the catheter is introduced via a sheath in the femoral artery, and is advanced up the abdominal aorta, over the aortic arch, and dye is then injected into the coronary arteries. For the radial site, the right radial artery is most often used. The catheter is advanced up the right radial, brachial, axillary, and subsequently the subclavian artery. The aortic arch does not nave to be navigated. If the left radial artery is utilized, then the arch must be navigated, as well.
The coronary arteries typically arise from the aortic root, right above the aortic valve. Bypass grafts, however, are sown into different locations in the aorta, above the native coronary arteries. A common type of bypass graft, the internal mammary artery (IMA), actually comes off of the subclavian artery, which supplies blood to the arm. The most commonly used graft to the left anterior descending coronary artery is the left IMA.
The most likely reason why your physician recommended against a radial artery catheterization in your case is that your bypass anatomy was not known. If the right radial artery was used, it would be difficult to navigate into your left subclavian artery to inject the left IMA. Similarly, if the left radial artery was used, it would be difficult to navigate to the right IMA. While it can be done, it is often quicker and technically safer to use the femoral site in this circumstance. If your coronary and bypass anatomy is known, then it is more likely that the proper radial artery will be used for access so that the case can be completed efficiently. There is some difference of opinion on this matter, however, and as such you may have been given different information by different providers.
I hope this information is helpful. Best wishes!
Interesting and very timely question from my point of view. A stress test indicates I have a new LAD blockage in probably a risky setting, maybe two blockages. I know that my doctor often uses the radial artery, so asked why my procedure next week will be in the femoral artery. His answer was interesting. First, he knows my 'real estate' well from previous femoral angiograms, and also suggested that this attempt would very likely be pretty vigorous and my arms and hands are very fragile... he wants to spare me from some very serious swelling/bruising. My nuclear 'time clock' has expired so he won't be taking his time.
This latest blockage came on fast and furious. Email me privately if you wish and I'll tell you more.