Hydrophilic-Coated Radial Sheaths: A Leap Forward, But Watch Where You Land.
Ian C. Gilchrist, Mark Kozak, Pennsylvania.
Radial artery spasm is one of the impediments to transradial cardiac catheterization. Although the incidence of spasm as a reason for procedural failure appears to markedly decrease with operator experience, it never completely disappears. In addition to preventing the completion of the procedure, spasm causes pain and discomfort, thereby offsetting one of the main advantages of the radial approach.
One recognized technique to reduce the problem of spasm has been to use hydrophilic-coated sheaths. Whether these coatings truly prevent or diminish spasm by their presence, or make the catheter impervious to traction from the muscular arterial wall is unclear. In this issue of JACC: Cardiovascular Interventions, Rathore et al. (1) have added to our understanding of this concept by showing that length of the arterial sheath is not a factor in producing symptoms of spasm when hydrophilic sheaths are used.
There has been a long-standing debate among radialists about the importance of sheath length with little data to illuminate the issue. The present study confirms the importance of hydrophilic coatings. It also supports the notion that length is not important. This implies that spasm occurs in the distal segment of the radial artery where the ratio of sheath-to-artery diameters is greatest and where the actual trauma of puncture occurs. This is consistent with the observation that when catheter size is reduced, the incidence of spasm is also reduced.
Beyond symptomatic spasm, the long-term health of the radial artery is also a concern with transradial procedures. Radial occlusion is usually asymptomatic and may be transient, but there are also concerns about changes in the vascular wall that could cause chronic dysfunction and prevent future use of the artery as a coronary conduit or renal shunt. The effects of a longer sheath on radial function could be either protective or harmful, but the question remains unanswered, as radial function and ultrasound studies were not included in the present study.
Nitrates and/or calcium blockers are typically used to prevent spasm in clinical practice, but in this study, they were withheld unless symptoms occurred. This probably accounts for the relatively frequent 19% to 40% rate of spasm noted in this trial and probably amplified the effect hydrophilic sheaths might actually have in the setting of practice where spasm is treated prophylactically. The need for adequate anticoagulation is also confirmed as the rate of vascular occlusion was significantly increased in patients without routine heparin use. The risk of bleeding is minimal with radial catheterization, but thrombosis and radial occlusion are hazards. Full anticoagulation is critical to prevent radial thrombosis.
Hydrophilic sheaths have been available for 10 years, yet their acceptance has been slow. Part of the problem has been the appearance of foreign body reactions in some patients after hydrophilic sheaths were used. Rathore et al. (1) noted this reaction in approximately 5% of their subjects. At times, this type of reaction is just a minor inconvenience to the patient, but in others, it can be very painful and require prolonged therapy before resolution as shown in Figure 1. In essence, the use of hydrophilic sheaths may involve trading the short-term pain and procedural disruption of spasm, for the longer-term pain and discomfort from the care of a sterile abscess. These sequelae are clearly unacceptable to the radialist who is trying to reduce patient discomfort and streamline the care process.
Figure 1 Sterile Abscess After Hydrophilic-Coated Radial Artery Sheath
Several weeks after radial cardiac catheterization with a 6-F Cook hydrophilic sheath, a sterile abscess formed between the skin and radial artery. The patient had local pain without systemic symptoms. This was treated with surgical drainage and local skin care with resolution over several weeks.
Provided with permission from I. Gilchrist.
The foreign body reaction appears to be set off by the shedding of the gelatinous hydrophilic material of the sheath as it enters the radial artery. The gel then remains deposited in the confined subcutaneous space between the artery and skin. Initially, the entry wound heals without apparent problems, but then several weeks after catheterization, the patient returns with a sterile abscess. Local drainage without antibiotics is curative, but at times, the presentation has been confused with more serious conditions resulting in rehospitalization, surgery, and intravenous therapy.
Fortunately, this foreign body reaction is not a class effect of hydrophilic sheaths as each manufacturer of these sheaths has their own proprietary manufacturing process and compounds. The sterile abscess and foreign body reaction appears to be associated specifically with the Cook Medical, Inc. (Bloomington, Indiana) AQ hydrophilic-coated sheath used in this study, and apparently in all published reports of this reaction. This particular sheath is associated with similar reports in the U.S. Food and Drug Administration MAUDE (Manufacturer and User Facility Device Experience) database (2) and was the subject of regulatory alert in Europe (3). After we reported the largest series of these foreign body reactions (4), we stopped using this product. Since then, using non-Cook hydrophilic sheaths, we have not seen any more foreign body abscesses after several thousand procedures, and others have reported the same (5).
How do experienced radialists manage spasm? Prevention is best. Avoidance of radial surface contact with the sheath by using the smallest feasible diameter for the vascular access is one approach to lessen spasm. Vasodilator medications are probably best given prophylactically before symptoms occur, but optimal therapy requires further study. Sheath length is not important, but hydrophilic coatings do appear to be protective against spasm. Once a wire is passed to the central system, further catheter exchanges should be accomplished over the wire so wires do not repeatedly cross the radial artery. Wires used for catheter exchanges should be coated with polyfluoroethylene or similar agents to reduce friction as uncoated, bare-metal, wires in the arm arteries tend to mechanically induce spasm. Spasm, if not prophylactically prevented, should be addressed with adequate analgesia and more vasodilator medications. These can be delivered through the sheath sidearm, through the lumen of the coronary catheters, or wiped on the surface of the catheters. Finally, downsizing of the diameter of the cardiac catheters can be tried to further reduce the physical pressure of the catheters on the arterial wall. If spasm prevents the completion of a radial procedure, the contralateral radial artery can be tried, as this is probably safer than a femoral puncture under the circumstance of system anticoagulation.
Although acute spasm and its management are fairly well described and controllable, the factors that drive long-term damage to the radial artery remain unknown. A few reports suggest possible longer-term damage to the radial artery walls from catheter procedures. This alteration in the radial artery may occur both at the site of entry and along the course of the indwelling sheath (6). Whereas catheters close in size to the arterial lumen appear to represent a logical hazard, little systematic evidence has been gathered to define the syndrome and therapies that might modify its occurrence. Perhaps long drug-coated sheaths do have a role in protecting arterial endothelium; with the present dataset, we cannot determine the answer and future trials are needed. As we leap forward, we need to watch where we land so that our footprints do not add further vascular damage to the radial artery.
J Am Coll Cardiol Intv, 2010; 3:484-485.