Fundamental Issues To Be Addressed Before And During A Transradial Procedure
Hakim Benamer, Thierry Lefèvre, Neus Salvatella, and Yves Louvard.
Institut Cardiovasculaire Paris Sud, Massy, France

Introduction

TRA is being increasingly used in Europe. Currently in France, more than 60% of patients undergo PCI using the TRA. In “radial” centers, this percentage may be as high as 90%. In the future it will probably become the gold standard approach worldwide because it has been shown to improve, comfort of the patient, to reduce access site complications, hospital stay and to decrease cost. The main limitation is the learning phase as the radial artery is relatively small and more difficult to puncture and cannulate than the femoral artery, anatomic variations are more frequent and  catheters manipulation and handling are different.

Patient selection:

in high femoral risk patients such as hypertensive or obese patients, patients with peripheral disease, patients on coumadin or GP2b/3a inhibitors). Old patients or acute myocardial infarction patients are also at high femoral risk but this need more TRA experience.  
The radial artery is superficial and manual compression is very easy. There is no nerve or significant vein in the puncture area. The formation of an hematoma is unlikely due to the absence of soft tissue and direct access to the radial artery2. The radial artery is a relatively small vessel: 2.66±0.44 mm on average according to Yoo et al (2003)., 2.69±0.40 mm in men and 2.43±0.38 mm in women3. More than 80% of women can accommodate a 6 French introducer in their radial artery vs. more than 90% of male patients (Figure 1). For 7F introducers the percentage is >60% in women and >80% in males. The fact that 6F devices can be used in the vast majority of cases, allows the operators to carry out simple angioplasties as well as complex procedures4, such as interventions in coronary bifurcations with kissing balloon inflation5, or rotablator procedures (up to 1.75 mm burrs6, 7), thrombo-aspiration and angioplasties of saphenous vein grafts with distal protection devices8. In the few cases where the use of 6F catheters is impossible or painfull, a 5 french guiding catheter can be used or a specifically designed catheters may be used to perform angioplasty without introducers9. In all cases, barring specific contraindications, the TRA does not preclude the use of the femoral approach after the coronary angiogram has been performed or in case of a staged procedure.

Figure 1: Radial Artery Diameter in male and female and compatibility with PCI

Today, there are many arguments in favour of the TRA: decreased risk of bleeding and vascular complications10, possibly low mortality as shown in the MORTAL study11, improved comfort for patients12 as well as for the paramedical staff, and reduction in hospitalization duration13 and patient management costs12. The risks of vascular complications and bleeding are higher in certain patient populations14. Indeed, the TRA is particularly beneficial in elderly15, low-weight and obese patients who are more prone to vascular complications16-19. The study by Louvard et al15, clearly underline the advantages of this approach in octogenarians as evidenced by a lower rate of bleeding and vascular complications and subsequent earlier patient discharge. Similarly, a correlation has been shown between patient weight and bleeding and vascular complications (U-curve), with an increased risk in very low-weight and severely obese patients16-19. As demonstrated in the TROP registry, the TRA has become the gold standard approach for many experienced teams16.
The medication used tends to impact on complication risks, especially antiplatelet agents20, 21 which are increasingly potent in combination with anti-thrombotics22, 23. This is illustrated by the current problems posed by the administration of new antiplatelet treatments which are clearly efficient in reducing the rate of cardiac events, but are also associated with a higher frequency of bleeding complications often related to the femoral approach24, 25. The reduction in vascular and bleeding complications associated with the use of femoral closure systems remains controversial and relatively modest or non significant compared to the clearly demonstrated efficacy of the TRA26, 27.

Currently, the TRA is the preferred option for both coronary angiography and coronary angioplasty in many European centres. However, some patients are still explored or treated via the femoral approach in instances where the use of ³7F devices is judged necessary, in case of double pediculated mammary artery graft (sometimes done by transradial approach28), non-palpable radial artery, presence of fistulae in dialysis patients.
In order to ensure a smooth learning period, beginners are advised to select simple cases, namely young male patients, with an easily palpable radial artery, in a non-emergency setting29. The degree of procedural complexity can be gradually increased with procedures involving older patients, female and obese patients, moving on to an emergency context with patients presenting at the acute phase of myocardial infarction.

Figure 2: Learning Curve for Right Radial Approach

Failure to comply with the requirements of the learning curve may lead inadequately prepared operators to abandon the radial approach (Figure 2)29. Each stage of the learning period must be completed methodically under the guidance of more experienced colleagues. The TRA using the left radial artery is probably less complex because selective catheterization of the coronary ostia is very similar to the femoral approach and there is less subclavian tortusosities. On the opposite, TRA using the right radial artery is more convenient for the back of the operator and reduces the interventional cardiologist’s exposure to X-rays as he/she is able to move away from the radiation source more easily30.

Figure 3: The Allen Test

Patient preparation and set up:
Appropriate patient preparation is very important. The patient must be adequately informed so that any stress related to the procedure may be avoided. Patient information is also a legal requirement in many countries. A mild sedative and anxiolytic medication is often administered. In some centres, the application of a Lidocain cream (Emal), at least two hours before puncture reduces pain and may even replace the subcutaneous injection of xylocain used for local anesthesia.
The patient must be comfortably laid and the wrist should be extended on an arm board. Patient set up varies according to the puncture site. When the left arterial artery is selected for puncture, certain cardiologists place the patient’s arm on his stomach after performing the puncture in order to facilitate catheter handling. X-ray protection requirements must also be taken into consideration.
Before puncturing the artery, carefull palpation of the radial artery must be performed by comparing both sides. The operator must be able to assess the arterial diameter in relation to pulse intensity. In patients with very small radial arteries and thin wrists, especially in short women, it is often preferable to select the femoral route. These are, however, infrequent instances. It is to be noted that the radial artery is sometimes (about 1%), very lateral and superficial and more difficult to puncture (dorsal radial artery).

Anaesthesia:
Patient preparation starts before arrival in the cath-lab with administration of a pre-medication. Comfort is obviously improved in the cath-labs where anaesthetists are available. In a double blind randomized study, we demonstrated that the use of remifentanyl (a morphine agent with a short duration of action) with a systematic target controlled infusion (1.5 ng/ml) was superior to the administration of sedatives or pain medication on request using bolus of midazolam (1 mg) or alfentanil (0.5 mg) when needed35. Indeed, in remifentanyl group, the occurrence of pain and subsequent spasm was significantly less frequent. In this study, spasm was quantified by the interventional cardiologist on a visual analog scale (Figure 4) and sheath extracting force (Figure 5) by using a micro-dynamometer (Pesola, Switzerland). It is, therefore, crucial to prevent, and treat, the vicious circle of pain-spasm-pain, because radial spasm was correlated to pain in this study35.

Puncture:
Radial puncture is a very important step. For a very long time, it constituted one of the main difficulties and cause of failure. In the initial series presented by Barbeau et al. in 1999, failed attempts were reported in 7% of patients with puncture being the cause of failure in 69% of cases31. Failure was more common in females, elderly and obese patients. The failure rate was shown to decrease rapidly with time and the increasing experience of the interventional cardiologist. Considerable progress has been achieved in this field due to the availability of new dedicated devices, and once the learning curve has been completed, puncture failure is currently reported in less than 1% of cases29.

Figure 4: Anesthesia In Trans-radial Approach Intensity of Spasm

Figure 5: Anesthesia In Trans-radial Approach Intensity of Pain

Puncture should be performed in a quiet environment with a serene and pre-medicated patient. Local anaesthesia is carried out, sometimes following application of lidocaïn cream36. Anesthesia is administered at the site of the radial artery with a very thin needle for subcutaneous injection and consists of a small amount of xylocain (1 to 2 ml). After a few minutes, the puncture is performed either with a venous cannula or with a bare needle37. In all cases, the puncture must be performed carefully and calmly and never hurriedly. The puncture angle between the sheath or the needle and the skin should be approximately 30°37. Occasionally, the radial pulse gradually decreases and becomes silent which renders puncture very difficult or even impossible. In such cases, consecutive sequences of humeral occlusion by compression restores the radial pulse by reactive hyperemia. Other authors have suggested to use a subcutaneous injection of nitrates to ensure radial vasodilatation and improve pulse palpation38. Once the sheath venous cannula or the needle has been positioned, a wire is inserted into the radial artery. Hydrophilic wires are used in sheaths in most cases and metallic wires in needles in all cases (to prevent the risk of wire sectioning).

Sometimes, despite the presence of adequate pulsated blood flow, the guide wire may encounter some resistance in the radial artery. In such instances, the operator should bend the wire into a ‘J’ shape to facilitate guide wire navigation through potential loops, avoid small dividing branches or blocking against the posterior wall of the radial artery. Significant arterial tortuosities may be the cause of potential difficulties and the operator may have to perform a more proximal puncture. Once the guide wire has been adequately inserted into the radial artery, the sheath is positioned. Some operators make a skin incision with a small scalpel. In most cases, given the quality of the introducers, cutaneous incision is no longer necessary.
The possibility of doing repeated transradial access for cardiac catheterization procedures is controversial but many studies have shown that it is safe and efficient3, 39 and associated with a low rate of failure.

Cocktail:
The injection of a medication cocktail in the radial artery is aimed at reducing spasm and decreasing the risk of thrombosis. The intra-radial injection of verapamil, a calcium inhibitor, at a dose of 2.5 to 4 mg has been clearly shown to be efficient in reducing the risk of spasm and is often combined with injection of heparin 5000 IU or 50 IU/kg, thus allowing a reduction in the risk of secondary thrombosis of the radial artery40, 41. Nitrates can also be administered to reduce the risk of spasm further. In order to minimize the burning sensation feeled by the patient during injection of verapamil, it is recommended that the cocktail should be injected gradually by mixing it with blood.

Potential Difficulties:
Puncture is achieved quite effortlessly in some cases, but in other instances the presence of significant calcifications in the radial artery may complicate or even preclude sheath insertion. Calcifications are visible by X-ray examination. Such abnormalities are frequently observed in diabetic patients42. The position of the radial artery may be atypical, namely, dorsal. This should be anticipated in cases where the radial artery is hardly palpable in the normal position. The dorsal radial artery is quite accessible. However, the puncture should be performed by mobilizing the artery between two fingers in order to prevent it from ‘rolling’.

Loops constitute one of the major difficulties associated with the TRA43. Though, less frequently present in the radial artery itself, their presence cannot be completely excluded. They can be identified by contrast injection, which should be carried out in cases where friction is felt when inserting the guide wire. In such instances, the crossing should be performed with a 0.25’’ hydrophilic wire or a coronary angioplasty guide wire. Loops are more frequently observed at elbow level (radial-cubital loops). There are other potential anatomical variants44, 46 which should be anticipated: radial artery stemming from a high position, sometimes in the subclavian artery (Figure 6)43. Loops may also be observed in the subclavian artery and more frequently in the right side. The frequency of loops increases with

age and presence of arterial hypertension. Sometimes, loops require the use of 0.38″ stiff wires . Other difficulties such as atheromatous lesions on the humeral or subclavian route or in case of arteria lusoria may be encountered47 (Figure 7). These anatomical variants may cause significant friction which hampers guide wire navigation

Figure 6: Radial Artery Variations

Figure 7: Arteria Lusoria

and sometimes mistaken  as spasm. The difficulty can be solved optimally by careful contrast injection in the forearm or arm, avoiding dissection. The guide wire should be selected according to the anatomical configuration. An angioplasty guide wire may be used to cross certain cubito-radial loops successfully. Forceful advancement of an inappropriate guide wire may result in vessel perforation with serious, though infrequent, consequences such as haematoma with compartment syndrome of the arm. In cases of vascular injury, the perforated area should be identified by X-ray and adequate compression applied immediately (a large elastic adhesive band is very usefull).  Another problem associated with guide wire advancement is the inadvertent insertion of the guide into vessels of the neck with a subsequent risk of stroke. X-ray guidance of guide wire advancement is very important at this step.