The benefits of the transradial approach have clearly been documented in numerous studies in the past ten years.1-9 Access site bleeding complication rates are lower and early ambulation results in a significant reduction in patient morbidity and a lower total procedure cost.3,4 Both patients undergoing the procedure and staff caring for these patients overwhelmingly prefer the transradial approach.10
As a result of these benefits, there has been an increase in the use of the radial artery for interventional procedures worldwide in the past several years. This experience has led to an understanding of the problems and complications that can result from the transradial approach. The purpose of the present manuscript is to review these issues.
Radial artery occlusion
Although this complication is a major concern, the consequences of radial artery occlusion are usually benign. The dual blood supply to the hand is an extremely protective mechanism (Figure 1). Hand ischemia with necrosis has occurred following prolonged cannulation of the radial artery for hemodynamic monitoring in critically ill patients; however, this complication has not been reported thus far after transradial coronary procedures.
The absence of ischemic complications is largely the result of the original recommendation by Kiemeneij that the transradial procedure be performed only in patients with a documented patent ulnar artery and palmar arch.1 This has traditionally been evaluated using the Allen’s test, but ultrasound, Doppler, and plethysmography prior to the procedure are more accurate methods.11
Plethysmography is probably the simplest and most effective method. A pulse oximetry test is performed with the probe placed on the patient’s thumb (Figure 2). The persistence of waveform and high oximetry readings after digital occlusion of the radial artery is very strong evidence that the patient will have sufficient collateral flow to prevent hand ischemia if the radial artery should become occluded as a result of the procedure. Barbeau has demonstrated the reappearance of the waveform and a high oximetry reading two minutes after initial negative results.11 This delayed recruitment of collaterals may be an additional explanation for the absence of hand ischemia with radial occlusion.
Several variables influence the incidence of radial artery occlusion. Adequate anticoagulation is extremely important. This is usually not an issue in patients undergoing interventional procedures, but the incidence of radial occlusion was as high as 30% in patients receiving only 1,000 units of heparin during diagnostic catheterization.12 The incidence of radial occlusion is reduced significantly by administering at least 5,000 units of heparin during the procedure.12,13 Due to this risk of radial occlusion, we tend to reserve the use of the radial artery for interventional procedures and look-see diagnostic catheterization. Elective diagnostic catheterizations are performed transradially only when there is an increased risk of femoral complications.
Catheter size has been shown to be an important predictor of post-procedure radial artery occlusion. Saito has studied the ratio of the radial artery internal diameter to the external diameter of the arterial sheath.14 The incidence of occlusion was 4% in patients with a ratio of greater than 1, as compared to 13% in those with a ratio of less than 1. Radial procedures have traditionally been performed using 6 Fr catheters, and most patients have an internal radial artery diameter larger than the 2.52 mm external 6 Fr sheath diameter.14 The incidence of radial occlusion following 6 Fr procedures is less than 5%, but the rate increases with larger sheath sizes.4,13 Virtually all interventional procedures can now be performed through large-bore, 6 Fr guide catheters, and larger-sized catheters are rarely necessary. For straightforward procedures, 5 Fr guide catheters may be utilized and are particularly useful in smaller women.
When the radial artery is utilized for hemodynamic monitoring in critically ill patients, the incidence of radial occlusion is significantly higher in patients with cannulation times greater than 24 hours, as compared to those under 20 hours.15 Since catheters are virtually always removed at the conclusion of a catheterization or interventional procedure, the time of cannulation may not be a factor. However, prolonged post-procedure compression times, particularly with high pressure using a mechanical device, may be a factor. We use sufficient pressure only to achieve hemostasis and try to remove the device as quickly as possible. Even in patients with intensive anticoagulation, it is rarely necessary to maintain mechanical compression for longer than one to two hours. A compression dressing using non-occlusive pressures can then be applied.
In summary, post-procedure radial occlusion occurs only in a small percentage of patients and is virtually always asymptomatic because of the dual blood supply to the hand. Patients with generalized vascular disease, diabetes mellitus, and those undergoing repeat procedures are more susceptible. The incidence can be minimized with appropriate anticoagulation, proper sheath selection, and avoiding prolonged high-pressure compression following the procedure.
Non-occlusive radial artery injury
Recent studies have demonstrated that permanent radial artery injury without occlusion may occur following transradial intervention in some patients. Mean radial artery internal diameter as measured by ultrasound was smaller in patients undergoing repeat transradial interventional procedures as compared to the initial procedure.16 This smaller diameter was not present on the day following the procedure, but developed during a mean follow up of 4.5 months. Wakeyama et al. demonstrated with intravascular ultrasound that this progressive narrowing is due to intimal hyperplasia, presumably induced by trauma from the cannulation sheath or catheter.17 The studies in our laboratory show that this hyperplasia is usually segmental rather than diffuse and is not present in all patients with a previous transradial procedure (Figure 3). The incidence of subsequent intimal hyperplasia in patients undergoing radial procedures is yet to be determined.
The ramifications of this injury are important not only in patients undergoing repeat interventional procedures, but also in patients in whom the radial artery may be used as a conduit for coronary artery bypass surgery. At our center, this is not an issue as most procedures are performed from the right radial artery and surgeons use the left radial artery for bypass graft purposes. At present, it would seem prudent not to use a radial artery that previously has been used for a catheterization as a bypass graft.
Radial artery spasm
Much of the morbidity of the transradial procedure is related to vasospasm induced by the introduction of a sheath or catheter into the radial artery. The vessel has a prominent medial layer that is largely dominated by alpha-1 adenoreceptor function.18 Thus, increased levels of circulating catecholamines are a cause of radial artery spasm. Local anesthesia and adequate sedation to control anxiety during catheter insertion are important preventative measures.
It has been demonstrated in isolated radial artery ring segments that nitroglycerin and verapamil are effective agents in preventing arterial spasm.19 Indeed, a vasodilator cocktail consisting of 3-6 mg of verapamil injected intra-arterially prior to sheath insertion is extremely effective in preventing radial artery spasm. The effect of the drug is immediate and significant arterial dilatation can be seen within minutes of its administration (Figure 4).
Intra-arterial verapamil and nitroglycerin have virtually eliminated vasospasm as a cause of significant morbidity of the procedure. It is now possible to perform transradial procedures using short sheaths and arm discomfort generally occurs only in patients with very small or tortuous radial arteries, particularly if guide catheter manipulation is excessive.
Spasm distal to the access site may be a cause of access failure. Occasionally, guide wire or guide catheter induced focal spasm may occur in a tortuous segment. Angiographic visualization of these areas is important as they generally respond to repeat verapamil administration and can be traversed with an angled hydrophilic coated guide wire. A soft-tipped coronary guide wire may also be used to cross these areas (Figure 5).
Sheath induced spasm is also minimized by the use of sheaths with hydrophilic coating. Kiemeneij has documented that both patient discomfort and the force required to remove a sheath as measured by an automatic pull-back device was significantly less with hydrophilic coated sheaths as opposed to non-coated sheaths.20
Local access bleeding
The most important benefit of transradial procedures is the elimination of access site bleeding complications.1-4 The radial artery puncture site is located over bone and can easily be compressed with minimal pressure. Thus, bleeding from the radial access site can virtually always be prevented. Although manual pressure from an experienced operator is the ideal method to obtain hemostasis, several compression devices have been developed in an attempt to maximize operator and staff efficiency. Local hematomas may occur as a result of improper device application or device failure. It is important to emphasize that compression of the radial artery both proximally and distally to the puncture site must be performed because of retrograde flow from the palmar arch collaterals.
Bleeding may occur from a site in the radial artery remote from the access site. The most common cause is perforation of a small side branch by the guide wire in patients receiving a platelet glycoprotein IIb/IIIa inhibitor (Figure 6). Avulsion of a small radial recurrent artery arising from a radial loop is another important cause of this syndrome.21,22 Hydrophilic guidewires preferentially select this small arterial remnant in patients with a radial loop and forceful advancement of the guide catheter can result in avulsion of the vessel. Radial artery perforation has been described in 1% of patients although in our experience the incidence is substantially lower. A low threshold to perform a radial artery arteriogram when any resistance to guide wire or catheter insertion is encountered will help prevent this complication.
Recognition of this bleeding remote from the access site is important as hemostatic pressure must be applied to an area other than the access site. Hemostasis is usually easily accomplished by the application of an Ace bandage to the forearm. A blood pressure sphygmomanometer may also be utilized. The latter is inflated to systolic pressure and then gradually released over a period of one to two hours. Sealing of a perforation with a long sheath is also an option, but this is rarely necessary.22
Compartment syndrome is the most dreaded complication of radial artery hemorrhage. A large hematoma causes hand ischemia due to pressure-induced occlusion of both the radial and ulnar arteries. Fasciotomy with hematoma evacuation must be performed as an emergency procedure to prevent chronic ischemic injury. This complication is rare, occurring only once in our early experience; it should always be preventable.
Failure to cannulate the radial artery using a 20 gauge needle and a 0.025 mm straight Terumo guide wire occurs in less than 5% of patients with an experienced operator. The importance of adequate patient sedation and local anesthesia in the prevention of radial artery spasm has previously been emphasized. In addition, meticulous attention to detail is important as the probability of failure increases as the number of unsuccessful attempts to puncture the artery increases. It should be emphasized that the puncture site is proximal to the styloid process of the radius bone. The radial artery distally usually bifurcates and becomes less superficial and attempting to puncture the vessel too distally is a common cause of access failure (Figure 7).
The radial loop is the most common congenital anomaly of the radial artery and may be a cause of access failure. It occurs in 1-2% of patients and may be unilateral or bilateral.21 Wide loops can occasionally be traversed with hydrophilic guidewires and 5 Fr catheters without excessive patient discomfort.23 However, in most cases, it is preferable to consider an alternative access site.
Radial arteries that are smaller than 2 mm in diameter are difficult to access. These are generally seen in smaller women and patients with previous radial procedures. The use of a 5 Fr guide in this situation may be an option. However, complex or difficult procedures cannot be performed through a 5 Fr guide catheter.
Pseudoaneurysm formation may rarely occur at the radial artery access site. This is usually easily managed with thrombin injection and/or mechanical compression. However, surgery may be required. Radial artery avulsion due to intense spasm has been described but this complication should virtually never occur using contemporary techniques. Sterile abscesses rarely occur with the use of hydrophilic coated sheaths.24
The radial artery is an excellent access site for coronary interventions. Although technically more challenging with a definite learning curve, there are significant advantages to this approach. Complications are infrequent and many are preventable with careful technique.
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