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Radial Approach Overview

The Body's Highway
Interventional medicine, or catheter-based therapy, utilizes the body's circulatory system as a "highway" -- and avoids open surgery by threading catheters into arteries and delivering medicine and devices to the affected areas from the "inside-out".

This highway can be accessed by several "on-ramps": the femoral artery in the groin, the radial artery in the wrist and the brachial artery in the elbow.

    tip of ordinary hollow catheter
hollow catheter tip

The Femoral (Groin) Approach
When attempting to access the coronary arteries to clear a blockage with a balloon, or place a stent to hold the artery open, the most often used entry point to the circulatory system has been the femoral artery. A small puncture is made with a hollow needle, which then allows a long tube, called a catheter, to be threaded into the femoral artery, up and around the aorta and into the coronary arteries. This femoral approach, sometimes called the Judkins technique (after Dr. Melvin Judkins who invented it in the 1960's) is the standard way in which most catheter-based procedures are done in the U.S.

However, there are some limitations to the femoral approach. The femoral or nearby arteries may be diseased and will not allow a catheter to pass easily. Sometimes a patient is overweight or obese, and the femoral artery is buried deep underneath the fatty tissue, making it hard to access, and then equally hard to compress after the procedure -- a necessary step in stopping the bleeding. In some cases, bleeding that is not immediately visible to the eye can occur in a backwards fashion into the body cavity -- this can be seen as a discoloration, like a bruise, that expands and must be treated. The possibility of involvement of the femoral nerve also exists. These types of complications are small in number, often quoted at 3%.

Invention of the Radial Technique
In the late 1980's, a French-Canadian physician, Dr. Lucien Campeau, started using the right radial artery, which is located in the wrist, as an entry point for diagnostic catheterizations. While the radial artery is slightly smaller than the femoral, it is still large enough to allow most catheters to traverse the distance to the coronary anatomy. In fact the radial artery was initially harvested and used in coronary artery bypass grafts.

By 1992 a group in Amsterdam, headed by Dr. Ferdinand Kiemeneij, had begun exploring ways to use the radial artery for interventional procedures, such as delivering balloons and stents. They were somewhat limited by the early equipment, but as catheters and stents became lower profile, thinner and easier to manipulate, the ability of physicians to use the radial artery increased. Most devices today can be delivered successfully using the radial artery.

Advantages of the Radial Approach
Most of the disadvantages of the femoral technique are nonexistent in the radial, also called the transradial approach. Even in obese patients, the radial artery is close to the skin surface, making the initial needle puncture simple and straight-forward. For the same reason, when the procedure has been completed, a short compression of the radial artery can stop the bleeding (achieve hemostasis) -- even when the patient has been aggressively anticoagulated with medicines to keep blood clots from forming, more and more common in the modern cath lab. Should any bleeding occur, it can be seen immediately. Finally, unlike the proximity of the femoral artery to the femoral nerve, the radial artery is not close to a major nerve, so the likelihood of "nicking" a nerve during the procedure is very low.

While complications are less common with the radial technique, the advantage experienced by all radial patients is that there is no longer any need to lie flat and still for 4-6 hours, or to experience what is sometimes a painful manual compression of the artery to curb the bleeding. Patients leave the catheterization lab and are able to sit up and walk almost immediately. Because of the simpler healing process for the arterial puncture in the wrist, certain patients may also be discharged home without having to spend the night.

The progress in the treatment of coronary artery disease has evolved to the point that when you compare heart bypass surgery from two decades ago with stenting done today via the transradial approach, what was a 4 hour major open heart operation, with general anesthesia, a week or more in the hospital and months of recovery, can now in some cases be performed as an outpatient procedure.

Is the Radial Approach for Everyone?
There are a few prerequisites for patients to be a candidate for the transradial approach. The first is confirmation of a dual, or "protected", blood supply to the hand. The radial artery loops around the hand and joins the ulnar artery. Both arteries supply blood to the hand and fingers. It is precisely this dual blood supply that makes the radial technique safe. Should the radial artery close up (a complication seen in a small percentage of cases) the clinical result tends to be benign, because the ulnar artery continues to function.

The first step a cardiologist takes in deciding on the radial approach is an Allen test to assess that both radial and ulnar arteries are functioning normally -- a simple test that can be done by compressing the arteries by hand at bedside or in the doctor's office. If they are not normal, then the femoral approach is preferred. Some other contraindications exist, such as the need to use larger devices during the angioplasty, pre-existing bypass grafts in certain areas or tortuous vessels that may prevent the catheter from navigating to the coronaries from the arm. About 30-40% of patients are not candidates for radial access.

    diagram of radial and ulnar arteries

While the complication rate with the radial approach is extremely low, there is always some risk with any medical procedure. It is important for patients to discuss the risks and benefits of the femoral vs. radial approaches, as these can vary for each individual.

Limited Utilization in the United States
The more frequent reason that patients are not offered the radial approach is that only a relatively small percentage of interventional cardiologists in the U.S. are trained in the technique. Parts of Europe and Japan do 40% or more of their cases using the radial artery, but in the U.S. estimates are in the low single digits -- although those U.S. cardiologists and radiologists who have learned the radial technique tend to use it for many, if not most, of their patients.

The reasons for this low penetration are several: lack of economic incentive due to the reimbursement structure, lack of patient awareness that this alternative exists, and lack of trained cardiologists. The situation, however, is changing. More and more practices are beginning to see the advantages in lower complication rates, increased patient satisfaction and even cost-savings (complications can be expensive to manage).

The femoral approach has been the gold standard for many years. Moving to the newer radial technique requires specialized training and advanced skills. Training opportunities are increasing as computer simulation models are being developed and a number of hospitals, both in and outside of the U.S. are now offering programs and mentorships. Current signs point to the increasing use of the radial technique in the U.S.

For the latest information on developments in the transradial technique, interviews with experienced practitioners and a list of training opportunities, visit our Radial Access Center.