Transradial Access at the University of Miami
- Volume 17 - Issue 9 - September 2009
- Posted on: 9/14/09
- 0 Comments
- 8008 reads
Dr. Mauricio Cohen has been performing transradial access procedures for approximately 5 years. After joining the University of Miami Hospital cath lab in January of 2009 as director, he instituted a transradial program.
Dr. Cohen, where did you first learn transradial access?
I was exposed to these procedures during my training in Argentina back in the mid-1990s. In 1994-95, we did a randomized study looking at radial, brachial and femoral access, and it was during this study that I was exposed to transradial access. I learned the nuts and bolts of the transradial procedure, but did not incorporate it into my practice until ten years later.
What’s your sense of how transradial access is utilized in Argentina?
I believe it is used slightly more than in the U.S., but not quite as much as in high-use countries like France, Canada, Spain or Sweden.
How often do you use transradial access in your current practice at the University of Miami?
I use it in 80-90% of my cases. When I approach a patient, the first thing I do is check the radial pulse. My mindset is that every patient is a candidate for transradial catheterization, unless contraindicated. Therefore, every patient is a radial case by default.
What are some of the reasons not to use the transradial approach?
There are very few contraindications for transradial access. These include the presence of an occluded radial artery, usually secondary to a previous procedure; lack of radial pulse; hemodialysis with an arterio-venous (AV) fistula in the forearm, and an abnormal Allen’s test. It is worth mentioning that we perform the Allen’s test using pulse oxymetry and plestismography to test the patency of the palmar arch. With this technique, less than 2% of patients will have an abnormal test. If there is previous coronary artery bypass graft surgery with a left internal mammary artery (LIMA) graft, we can puncture the left radial artery. As a matter of fact, engaging the LIMA is fairly simple and safe with this approach. If a patient has an occluded right radial artery, we will use the left radial artery, and then if we are unsuccessful, we will use a femoral approach.
How often do you find that you are converting to femoral access after beginning with a radial approach?
I’d estimate that occurs in less than 5% of cases. A common reason is tortuous anatomy. A tortuous subclavian would preclude access of the catheters to the ascending aorta. However, there are very few cases in which I have to convert because we are now able to negotiate the significant tortuosity associated with radio-ulnar loops, spasm or other problems that may present. I do think my rate of femoral conversion is actually decreasing.
How do you solve the problem of tortuosity?
It is important to keep in mind some basic rules when you do radials. You never push. Every procedure must be done with finesse. When we find that the wire is not going where it should be going or feel unusual resistance, we take a limited angiogram that will allow us to uncover the problem — anomalous anatomy or severe spasm. If it’s severe spasm, then we will give more vasodilators such as verapamil and nitroglycerin, and sedate the patient more. If it is a true anatomic problem, then we can sometimes use smaller wires and different catheters, such as a hydrophilic-coated catheter, to navigate the tortuousity, and then exchange for a stiffer wire that will straighten the vessel. Sometimes, when we cannot negotiate the tortuosity, we will convert to transfemoral access, but this is a rare occurrence. It is important that within one’s learning curve, the inexperienced operator be aware of his/her own limitations and convert to femoral access before causing a vascular perforation in case of very tortuous anatomy.
In general, we use 3 mg of intra-arterial verapamil in every case right after inserting the sheath. We use a dedicated access kit with a hydrophilic-coated sheath. It goes into the vessel very smoothly and I think it is less traumatic, so that’s an additional factor to prevent spasm. Sometimes we need to use additional doses of sedatives to prevent the adrenergic release associated with anxiety. We see spasm in 5-10% of cases, but in the past six months, I haven’t seen spasm severe enough to make me switch the access site.
When patients have severe vasospasm and severe pain, it may be a sign that there is a vascular anomaly, such as a radio-ulnar loop. Sometimes the catheter may have gone through a communicating vessel between the ulnar loop and the brachial artery. This communicating vessel is usually very narrow and reacts to the catheter with severe spasm. In these cases, when the patient feels severe pain, a limited angiogram helps us understand the problem.
When you are presented with challenges during radial access, why go the extra step of trying to work through them? Why not simply convert to femoral access?
We put in additional effort because the patient already has arterial access and because we believe that transradial access adds significant safety to the procedure. If you think you can safely negotiate the tortuosity, and feel confident it can be done with the equipment you have, I don’t see a reason for not doing so.
Is there a problem with excess contrast with transradial access?