Transradial Access in an Occluded Radial Artery: New Technique

Transradial access has gained popularity over the past decade due to its benefits such as improved patient comfort and decrease in access site bleeding complications. It is limited by difficulties that arise as a result of spasm as well as anatomic variations. Radial artery occlusion is a fairly infrequent complication of transradial access.¹ It is clinically quiescent in properly selected cases and rarely results in ischemia. It is probably related to the size of the catheter,^2,3 and more likely related to the ratio of the arterial diameter to the sheath.⁴ Despite its benign clinical course, it makes transradial access impossible from that radial artery. Certain factors have been found to affect its occurrence. Repeated cannulations predispose the patient to occlusion.⁵ Heparinization has been found to be effective in reducing the occurrence of radial artery occlusion.⁶ This has led to the suspicion that thrombus formation may be the mechanism, or at least the precursor, to the process leading to cessation of flow, although histologic proof of this does not exist. There are no reports of reaccessing the radial artery once it has occluded. We have now attempted radial access in 14 patients with documented radial artery occlusion and succeeded in 12 of these patients. We describe a representative case where radial access was successfully obtained in an occluded radial artery proven by ultrasonography or angiography. We also report the histopathologic findings of the occlusion-causing material extracted from the sheath.

Techniques

Baseline radial access procedure. After sterile preparation and draping and local infiltration with 2% lidocaine 3 finger breadths above the radial styloid process, a 20 gauge Teflon cannula was used to puncture the radial artery at a 45 degree angle. Blood “flash” in the transparent chamber marks the entry in the arterial lumen. The cannula was advanced further to perform counter puncture. The stylet was then removed from the Teflon cannula, and the 0.021 inch guidewire, which is part of the Radiofocus sheath (Terumo Corp, Tokyo, Japan), was placed in the hub of the Teflon cannula. The cannula was then gradually withdrawn until pulsatile flow was noted. At this point the guidewire was gently advanced into the cannula and the radial artery lumen. The Teflon cannula was then removed, and the Radiofocus glidesheath was advanced over the wire into the radial artery. All patients received 5 mg of diltiazem and 200 mcg of nitroglycerin. A majority of the patients received unfractionated heparin 50 units/kg, unless an absolute contraindication to anticoagulation existed. At the completion of the procedure, the sheath was removed immediately. Manual pressure was applied using a HemoBand (HemoBand Corp., Portland, Oregon) with a pledget made from a gauze-wrapped needle cap, placed under the band over the puncture site. Pressure was applied for 2 hours, then the band was gradually loosened. A dry gauze dressing without pressure was then applied.
Access technique for occluded radial artery. The wrist is prepared and draped in a standard manner, and after local anesthesia, a 20 gauge Teflon cannula is placed using throughand- through puncture in the very distal portion of the right radial artery, where a low-volume collateral flow pulse is usually palpable from the palmar arch. As the cannula is withdrawn, arterial blood is observed as a nonpulsatile dribble in the hub of the cannula. A 0.021 inch guidewire (Terumo) , which is a part of the Glide Sheath package, or a 0.018 inch micropuncture guidewire (Cook Inc., Bloomington, Indiana), is advanced into the cannula, and by gentle maneuvering, the pulseless portion of the radial artery is traversed under fluoroscopic guidance in order to follow the imaginary path taken by the radial artery, though its painless advancement is almost completely guided by tactile feel. If wire advancement causes pain, the wire should be withdrawn and readvanced. A previous radial angiogram is a significant help and may serve as a roadmap. A long Angiocath or micropuncture introducer (Cook) is advanced over the guidewire with gentle torquing motion. After removal of the guidewire from the microcatheter, pulsatile flow should now be present. The 0.021 inch guidewire is reinserted in the introducer and a Radiofocus Glide Sheath is carefully advanced.

Case Presentation. A 78-year-old diabetic female had unstable angina and an abnormal adenosine myocardial perfusion study. She underwent diagnostic catheterization via theright radial artery using the standard technique described above. She had distal aortic occlusion and a left mastectomy several years prior. Heparin was used in the diagnostic procedure at a dose of 50 units/kg (5,000 units). A 95% mid-LAD stenosis was noted, although due to azotemia, percutaneous coronary intervention (PCI) was staged. Seventy-two hours later, she was brought back for PCI. Her right radial pulse was not palpable at the previous puncture site, with a faint pulse felt distal to the original puncture site. The distal pulse was then cannulated and a postero-anterior projection angiogram was performed to delineate the mechanism of the abnormality. The findings are shown in Figure 1. A 0.021 inch guidewire was used from the Radiofocus sheath kit to wire the occlusion, which was surprisingly easy to wire (Figures 2 and 3). No pain was perceived by the patient. A long Angiocath Teflon cannula was placed over the wire and after removal of the guidewire, pulsatile blood flow was noted. Angiography of the proximal radial artery was performed to assess the condition of the lumen (Figure 4). The guidewire was placed back in the cannula and the cannula was removed. It was flushed to examine for any adherent content, and no debris was found. A 6 Fr Radiofocus sheath was advanced over the guidewire and the dilator was removed. No blood flow was present when the back-bleed valve was opened. Upon aspiration, a large piece of thrombus/tissue was removed from the sheath, after which good blood flow was observed. The intraluminal sheath position was confirmed angiographically. A 6 Fr EBU 3.5 guide catheter was used to perform primary stent implantation in the LAD with good success. At the termination of the procedure, the sheath was pulled back distal to the original occlusion, and an angiographically stable lumen was noted with no stenosis or evidence of impending reocclusion. The retrieved material was examined histopathologically and was found to be organizing thrombus (Figure 5). Several areas of the thrombus showed histopathologic signs of organization as evidenced by the presence of “nuclear dust”, and even the organization of channel formation which are precursors to capillaries.

Discussion
Radial artery occlusion is a limiting complication for the transradial interventionalist, as it makes radial artery reaccess impossible. Because of the natural macrocollateral circuit via the palmar arches, the distal radial pulse is very frequently palpable.⁷ It has been previously observed that the distal stump of an occluded radial artery has > 50% of the mean arterial pressure in 70% of the patients.⁸ This makes it possible to attempt accessing the distal radial artery lumen. Careful traversing of the occlusion, which in the case described above was fairly soft and negotiable, is possible using a straight-t ipped 0.018 inch/0.021 inch guidewire. This leads one to believe that the occlusion is caused by soft material, especially during the initial weeks following the culprit procedure.

Intimal medial thickening has been observed in the radial artery after transradial access using intravascular ultrasound.⁹ The radial artery entry site probably responds to injury in a similar manner to the post balloon dilatation response seen in the percutaneous transluminal coronary angioplasty model, with an initial thrombotic and subsequent proliferative response. As the risk of entering a false lumen or a side branch is present, graded entry with a microcatheter first, followed by confirmation of pulsatile flow and then introduction of the sheath, is probably the safest approach. This will avoid creation of a large perforation and its consequences. Although we did not need to use other equipment, polymertipped guidewires and other coronary equipment may also be used to facilitate radial access as mentioned above. The availability of a previous radial angiogram helps predict the path of the radial artery with subsequent attempts and increases confidence in advancing the guidewire along the path predicted by the previous angiogram. A previous radial angiogram was available in 4 of the 14 patients and was performed due to resistance to the passage of the J-tipped guidewire on the initial procedure. All 4 of these patients were successfully accessed in the second procedure.
This technique has changed our practice, with our group now using a slightly more proximal site of initial entry to provide for a future distal access site in the event of an occlusion. A straight-tipped guidewire is probably crucial to success, as in our 2 cases, we shaped the tip of the guidewire and probably entered subintimally, resulting in failure. We find the guidewire in the Radiofocus sheath kit to be the most suitable wire for this purpose. The guidewire is advanced purely based on tactile feel. Gentle forward pushing with slow-torque application is the technique we used for wire advancement. Close observation for even mild pain, which we noted in the 2 cases that failed and did not observe in the 12 cases that succeeded, is a must, as we believe false lumen passage will be associated with pain. Painless advancement of the guidewire with little or no initial resistance is a sign of true lumen entry. We advise using a nonhydrophilic guidewire for this purpose initially. In the 2 cases that we failed to recannulate, we were not able to determine the exactmechanism for failure. As with any other technique, there may be a learning curve associated with this technique as well. The histopathologic findings confirm the process of thrombus formation as the mechanism of early occlusion. A “plug” was aspirated in 5 out of 12 successfully-accessed occluded arteries. All of these arteries were occluded for less than 4 weeks. Hence, it is probably reasonable to attribute early occlusion to a process involving organizing thrombus. The surprising findings from the examination of this specimen was the rapidity of the process of organization of the thrombus with formation of neovascular channels, thus within a short period of time, the thrombus is probably replaced by hyperplastic tissue.

Limitations
The limitations of this technique include the blind nature of the initial procedure, and hence the risk of subintimal wire passage and perforation. Careful attention to even mild pain caused by the wire movement will help avoid this complication. The other potential risk is the possibility of embolization of the thrombus. Careful aspiration and forward injection only after establishment of free back-bleed will help prevent this complication.

Conclusion
Our report only describes the initial experience in 14 patients, and proves the fact that an occluded radial artery can be reaccessed using our technique. Furthermore, it is the first report to provide histopathologic confirmation of thrombus formation as the mechanism of the process of early radial artery occlusion following transradial access. Examination of a chronically occluded radial artery specimen obtained either during other surgical procedures or at autopsy may supplement this information by providing the evidence delineating the mechanism of chronic occlusion.