What is the difference between radial and femoral angiography?

Many invasive and interventional cardiologists in the United States prefer femoral angiography and angioplasty. This simply means that when they perform a procedure to see inside the arteries of the heart using x-rays (angiography) or treat an arterial blockage (angioplasty), they start by puncturing the femoral artery in the groin. Then they thread a slender tube, or catheter, through one artery after another until they reach the heart, just like following a roadmap with several twists and turns.
 A small but growing number of cardiologists perform the same procedures starting with the radial artery in the wrist. This approach is more common in Europe than in the United States, mostly because of longstanding training practices.
 The big disadvantage to the radial technique is that it takes longer to learn after being trained in the femoral technique. It also requires the use of smaller and differently shaped catheters.
 However, there is less risk of serious bleeding with radial procedures and they can be more comfortable for patients, especially during recovery. After a femoral procedure, the patient must lie perfectly flat for several hours. This is done to prevent excessive bleeding, but it can be uncomfortable for someone who has arthritis or back pain. After a radial procedure, a pressure band is applied to the wrist and the patient is advised to elevate the arm on pillows, but it is safe to sit up, walk around and use the restroom.