Congenital Coarctation and Takayasu’s Arteritis: Aortic Stenting Employing Intravascular Ultrasound
- Volume 13 - Issue 11 - November, 2001
- Posted on: 8/1/08
- 0 Comments
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The preceding report describes excellent results of stent deployment in a 23-year-old with coarctation of the aorta. My compliments to the authors for the superior result.
The diagnosis of Takayasu’s arteritis may be correct because of multiple vessel involvement, long segment narrowing and elevated phase reactants, although beginning signs of the disease in infancy and thoracic rather than abdominal coarctation may raise some doubts of the accuracy of the diagnosis. Whatever the basic diagnosis is, it is clear that there is definitive aortic obstruction causing significant symptomatology both during and after pregnancy. Thus, there is clear-cut indication to relieve the aortic obstruction. Of the three methods of intervention available at the present time, namely balloon angioplasty, intravascular stent and surgery, my preference is also stent, similar to that adopted by Kay et al. Discussion of reasons for such a choice is beyond the scope of this presentation.
However, the methodological approach that we take for the procedure is slightly different from that used by Kay et al. We generally perform the stent implantation procedure under conscious sedation instead of general anesthesia. We initially place sheaths in the right femoral vein and artery, perform diagnostic catheterization, and confirm the clinical and echocardiographic diagnosis. We do not use the additional left femoral artery site. After arterial entry, heparin is administered and the activated clotting time (ACT) is monitored and maintained between 200–250 seconds. Following measurement of pressure gradient across the coarctation, we perform selective aortic arch angiography using marker pigtail catheter (Cordis Corporation, Miami Lakes, Florida) with radiopaque markers 10 mm apart, so that accuracy with which the measurement of aortic segments are made is improved; this is not too dissimilar to that used in preceding report.
We would ordinarily attempt to perform the stent deployment through a much smaller sheath than the 11 French sheath used by the authors. The smallest sized sheath that will allow passage of a stent-mounted balloon catheter is selected. The reason for the selection of a smaller sheath is to avoid/minimize arterial damage. Even in the adult population, smaller sheaths have a lesser tendency to develop femoral artery occlusion.1 Based on the measurements obtained by the authors, a stent with an expanded diameter of 14 mm and a length of approximately 40 mm, as selected by the authors, is appropriate. Because of longitudinal rigidity2 and the potential for balloon rupture3 and arterial injury4 associated with Palmaz stents, we avoid using them. In this case, we would select a 36 mm long IntraStent DoubleStrut LD (IntraTherapeutics, St. Paul, Minnesota) for implantation. There is no discernable shortening of this stent with expansion. This stent is mounted on a 14-7 balloon-in-balloon (BIB) catheter (NuMED, Hopkinton, New York). This BIB catheter has an inner balloon diameter of 7 mm and an outer balloon diameter of 14 mm. The stent can be easily crimped on the deflated balloon of the BIB catheter and will pass through a 9 French sheath. Our preference is to implant the stent with a balloon diameter of the desired final stent diameter in order to prevent inadvertent dislodgement/displacement during placement of a second balloon catheter. Also, the expense associated with the extra balloon catheter is saved. Self-expanding (i.e., Wallstents) is another option,5 but we do not have any personal experience in the use of this stent.
Taking the above consideration into account, we initially place a 9 French long blue Cook sheath (Cook, Bloomington, Indiana) with a radiopaque marker at the tip and position the tip beyond the level of coarcted segment over an already placed, extrastiff 0.035´´ Amplatz guidewire (Cook). The selected stent is crimped onto the 14-7 BIB catheter and introduced carefully through the valve of the sheath without displacing the stent. The stent mounted balloon is advanced over the guidewire, but within the sheath and positioned such that the coarcted segment is centered onto the stent, using bony landmarks. The sheath is withdrawn, uncovering the stent. If there is uncertainty of the location of the stent, a test injection through the sheath is performed. Initially, the inner 7 mm balloon is inflated, and if necessary, the stent position readjusted, followed by inflation of the outer balloon, thus, implanting the stent. The pressure of inflation used is limited to the manufacturer’s recommended level. Both balloons are then deflated. The balloon catheter is gently advanced and the outer balloon re-inflated to ensure that the proximal end of the stent is well-positioned against the aortic walls. The balloon catheter is withdrawn into the sheath by advancing the sheath on the balloon as described elsewhere.6 Next, the balloon catheter is centered over the lower end of the stent, sheath tip withdrawn and outer balloon re-inflated, again to ensure that the lower end of the stent is well apposed to the aortic wall. The balloon catheter is removed (as described above). Throughout the above maneuvers, an assistant holds the guidewire in place. We then insert a 5 or 6 French monorail multi-track catheter (Braun, Bethlehem, Pennsylvania) over the guidewire.7 Pressure measurements across the stent are recorded to ensure relief of the pressure gradient. The catheter is re-advanced proximal to the stent and the angiography is repeated. If there is any discernable gap between the stent and aortic wall, a larger diameter balloon is positioned within the stent and inflated to ensure that the stent is well apposed to the aortic wall. Finally, the catheters and sheaths are removed and pressure dressing is applied. Alternatively, a vascular occlusion device8 is used to achieve arterial hemostasis. The patient is observed until the morning following the procedure and a chest roentgenogram and echocardiogram, along with Doppler, are performed prior to discharge. Platelet-inhibiting doses of aspirin (325 mg/day) are administered for 6–12 weeks.
In summary, I agree with Kay and his associates in regard to the choice of stent deployment for treatment of the long segment coarctation. The method that we use to implant the stent is slightly different in that we 1) use conscious sedation instead of general anesthesia, 2) utilize the 9 French sheath instead of an 11 French sheath for stent delivery, 3) employ a BIB catheter instead of two separate balloon catheters (Blue Max and XXL) to deploy the stent in an attempt to decrease the probability of stent displacement and reduce the cost, 4) select IntraStent DoubleStrut LD stent instead of Palmaz XL stent in order to prevent balloon rupture and increase stent flexibility, and 5) acquire post-stent implantation pressure and angiographic data via a multi-track catheter. However, Kay’s results are excellent, and I can’t argue with success.