Radial Approach To Cardiac Catheterisation

Coronary artery catheterisation is performed through two main routes: the femoral and radial arteries. Femoral artery access forms the traditional route while a third route namely, the brachial artery, involves a surgical cut down method is now largely defunct. This article looks at the basic radial artery anatomy, considerations for radial artery access – including patient care, advantages and disadvantages when compared with the more popular femoral approach.

Anatomy and procedure considerations

Anatomically, the radial artery (see figure A) can be traced from the brachial artery at the cubital fossa in the anterior aspect of the elbow. From here, the artery follows a lateral course of the arm, lying deep in the dorsal interosseous muscles and terminating at deep and superficial palmar arches where it joins with the ulna artery.

The first step in patient preparation, as is the case for all cath lab procedures, is to ensure that the patient understands the procedure and consents to have their angiogram via the radial artery. Patients undergoing the radial artery approach must have their pulse felt so that adequate blood flow to the hand can be established. In most departments, it is standard practice to perform an Allen’s Test. This test is done to assess the adequacy of ulna collateral blood supply which reduces the risk of ischaemia to the hand if the radial artery is compromised during a case.

Another important consideration is the radial board used. This is a very useful aid, even if a simple and rather inauspicious accessory, because it supports both the patient’s arm and the accessory equipment. It is important to position the board reasonably well at the start of the case - the operator/cardiologist will have a preference and would normally make recommendation here. A bag of saline or rolled up towel will help to support the patient’s elbow and wrist on the board making them relaxed and comfortable.

Radial boards come in different shapes and sizes. The decision to use one or the other is operator dependent. At least five types are available in my department. One of them (see fig B) will not be out of place among a professional surfer’s paraphernalia. However, this board has all the advantages described above and is the preferred choice in most cases.
The pointed end of the board is positioned under the shoulder of the patient while the wide end acts as support for the arm and wrist. It also acts a useful work top.

Vessel spasm and medication

Vessel spasm is a feature of radial artery catheterisation. Generally, there is a mismatch in diameter between the inner lumen of the artery and that of the sheath or catheter which causes friction. This friction (and related pain felt by the patient) is caused by manipulation of sheath of guide wire/catheter in the radial artery, Kiemeneij (2006). Other causes of spasm include tortuous artery, diseased vessels and small radial artery diameter.

Artery spasm can lead to a difficult and sometimes impossible radial procedure. There seems to be no standard range of drugs that accompany a radial approach. However, a cocktail of drugs are used to manage artery spasm during radial catheterisation as follows:

GTN (glyceryl trinitrate): contains nitric oxide which relaxes blood vessels thereby enhancing blood flow through the vessels. Some cath labs use ISDN (isosorbide dinittrate - marketed as Isoket) or other forms of the drug. They all perform the same function of dilating the radial artery and relieving pain.

Verapamil: (2.5mg strength) Verapamil is a calcium channel blocker. It blocks the entry of calcium ions in cells of the heart muscle, coronary and systemic arteries. Verapamil relaxes smooth muscles of the heart and blood vessels and is used to treat hypertension, angina and arrhythmia. The vasodilatory property of verapamil helps to reduce the incidence of arterial spasm that may occur during radial approach. Vasodilation will facilitate the passage of catheters and other accessories down the radial artery, resulting in the successful completion of a procedure.

As both Verapamil and GTN help to dilate blood vessels, patients should be monitored for associated drop in blood pressure. At high doses, verapamil can cause bradycardia, arrhythmia and heart block. Other side effects may include nausea and headache.

Heparin may also be given as part of the radial approach cocktail. It is an anti coagulant given to stop the formation clot within the blood vessels. Other medicines such as aspirin if given with heparin, can increase bleeding or increase the time it takes to stop bleeding. Caution must be taken where heparin is used in combination with other drugs.
Sedatives are also given to help relieve pain and to relax the patient. Other prophylactic and spasmolytic drugs (and sometimes anxiolytics) other than those mentioned above are also used.

Aftercare and haemostasis

After the radial procedure, the access site is cleaned, the sheath removed and compression applied over the puncture wound. Compression is done either manually or by using a closure device. Two main radial artery compression devices are in use.

These are

RADISTOP

This radial compression system (fig c) includes a Styrofoam support plate, Velcro strap and sterile compression pad. The support plate on the back of the hand/wrist helps to keep the hand straight such that the need to bend the hand and disrupt compression is prevented.

TR BAND

Two sizes are available: the regular 24cm and a 29cm long version for patients with bigger wrist circumference.
The device (fig D) is made up of an injection port, inflation syringe, Velcro strap and transparent dual compression balloons which ensure exact compression of the radial artery.

For both devices, haemostasis is easily achieved in the absence of any issues such as effect from analgesia on the patient, they can mobilise immediately and even walk from the lab and back to the ward.

• Fig A Fig A
• Fig B Fig B
• Fig C Fig C
• Fig D Fig D
•  

Advantages of radial approach

Lucien Campeau was the first person to describe radial artery catheterisation in 1989. Nearly twenty years on, technology has evolved to refine equipment and practitioner skills have advanced to offer many advantages to patients undergoing radial catheterisation. These advantages are:

1. The artery is easily accessible and is easy to palpate. Its superficial location also makes the artery easy to compress. This is particularly important in anticoagulated patients when the radial approach offers the best means of maintaining haemostasis.

2. Normal Allen test ensure collateral blood supply to the hand. Hence, any procedural occlusion in the radial artery is unlikely to compromise blood supply to the hand.

3. Radial approach provides comfort for patients because the procedure assures them the ability to mobilise. In fact, it is possible for patients who have undergone this procedure to walk from the lab table and back to the ward.

4. It is easier to notice and control bleeding from the radial artery. The femoral artery on the other hand lies deeper in the leg and compressing the artery can be difficult. In addition bleeding would be considerably significant by the time a haematoma is noted.

5. The limitations and risks involved via femoral approach in the presence of vascular disease and for obese patients are overcome in the radial method.

The importance of radial artery in coronary angiography is seen in relation to the femoral approach. Several studies have compared the two approaches.

For instance, Mann et al (1998) had earlier shown that there are less complications of bleeding from the radial artery which necessitates early mobilising and a shorter length of stay in hospital. Similarly, Archbold et al (2004) showed less access site complication in the radial artery. The authors also noted a preference of radial access over femoral by patients who have had angiograms through both routes previously and by managers because of the related reduced cost of radial cases.

Cost effectiveness of radial versus femoral approach has also been looked at recently by Roussanov et al (2007). This team reported that there is a significant financial benefit made (cost of vessel closure devices) for the radial artery approach.

Disadvantages of radial approach

Many of the disadvantages are related to the technical difficulties of performing the procedure.

These difficulties are the steep learning curve involved in perfecting the technique, problem associated with placement of the catheter, all of which may explain the general reluctance of operators to try and embrace a new approach.

Other disadvantages include the small size of the radial artery and the incidence of vessel spasm.

Radial artery access is not indicated for certain patients who have a negative Allen Test.

Patients who may require placement of an IABP (intra aortic balloon pump) may not be ideal for radial angiography.

Radial approach is also contra-indicated in patients for rotablation and other procedures that may require a larger sheath size;

Patients who have known vascular disease of the upper extremities.

Given the many benefits of radial catheterisation, one wonders why there are very few centres and cardiologists practising this technique. As stated by other observers, Williams (2008) also stated that the radial approach has a steep learning curve and the technique required is much greater than the femoral route. However, he observed that this problem can be overcome with experience and improvement in technology. Williams noted that ‘’although femoral arterial access is unlikely to become obsolete overnight, it may well be ultimately viewed as brachial access is today: a second line approach with an increased complication rate which is rarely required in routine practice’’

Williams is perhaps a bit overly optimistic, however, Campeau (1989) had modest expectations - when he first described radial angiography - in suggesting that radial approach could be safe and effective enough to rival and only replace the brachial route.

REFERENCES

1. Archbold, R.A., Robinson, N.M., Schilling, R.J. Radial artery access for coronary angiography and percutaneous coronary intervention. BMJ. 2004 21; 329(7463): 443–446.

2. Campeau, L. Percutaeneous Radial Artery Approach for Coronary Angiography. Catheterisation and Cardiovascular Diagnosis 1989; 16 (1): pp3-72

3. Kern, M.J., King 111, S.B., Douglas, J.S., Franch, R.H., Cardiac Catheterisation, Cardiac Angiography, and Coronary Blood Flow and pressure measurement. Chp17 in HURST’S THE HEART MANUAL OF CARDIOLOGY O’Rourke, R.A., Fuster, V., Alexander, R.W., King, S.B., Nash, I., Prystowsky, E.N. (Editors) (2005) 11th ed. McGraw Hill

4. Kiemeneij, F. Prevention and Management of Radial Artery Spasm. The journal of Invasive Cardiology 2006; 18 (4): pp159-160

5. Mann, T., Cubeddu, G., Bowen, J., Schneider, J.E., Michael Arrowood, M., Newman, W.N., Zellinger, M.J., Rose, G.C. Stenting in acute coronary syndromes: a comparison of radial versus femoral access sites. Journal of the American College of Cardiology, 1998; 32: pp572-576

6. Neal, M.J. (1992) Medical Pharmacology at a Glance. London: Blackwell Science

7. Rang, H.P., Dale, M.M., Ritter, J.M., Moore, P. (2003) Pharmacology. London: Churchill Livingstone

8. Roussonov, O., Wilson, J., Henley, K., Estacio, G., Hill, J., Dogan, B., Henley, W.F., Jarmukli, N. Cost Effectiveness of the Radial versus Femoral Artery Approach to Diagnostic Cardiac Catheterisation. Journal of Invasive Cardiology 2007; 19 (8): pp349-353

9. Swanton, R.H., Banerjee, S. (2008) Swanton’s Cardiology: A Concise Guide to Clinical Practice. Oxford: Blackwell Publishing

10. http://www.accumedsystemsinc.com/resources/radial_artery_access_manual.pdf Almany, S.L., O’Neill, W.W. Radial Artery Access for Diagnostic and Interventional Procedures. 1999 [Accessed 10/12/08]

11. http://www.bcs.com/pages/news_full.asp?NewsID=18866986, Williams, P. Femoral arterial access for coronary procedures - obsolete or here to stay? British Cardiovascular Society 11 November 2008 [Accessed 10/12/08].