What are the procedures for inserting a stent in the repair of coarctation of the aorta (CoA)?

Updated: Nov 20, 2018
  • Author: Syamasundar Rao Patnana, MD; Chief Editor: Stuart Berger, MD  more...
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Answer

The procedure may be performed under conscious sedation or under general anesthesia. Cardiac catheterization is performed to confirm the clinical and echocardiographic diagnosis and to exclude other cardiac defects. Pressure gradients across the coarctation and selective cineangiography in multiple angiographic projections are initially performed to demonstrate the stenotic lesions. [60]

The following measurements are made: (1) the diameter of the stenotic lesion, (2) the diameter of the aorta proximal and distal to the obstructive segment, and (3) the length of the vessel that can be stented. All the measurements are made in 2 orthogonal views and averaged. Foreshortening of the vessel length is taken into account based on the anatomy. These measurements are used in the selection of expanded diameter and length of the stent. Heparin (100 U/kg) is administered, and activated clotting times are monitored and maintained between 200-250 seconds by giving additional doses of heparin, as needed.

An end-hole catheter (5F-6F multi-A2) is positioned across the coarctation with the help of a soft-tipped 0.035-in Bentson guide wire. The guide wire and catheter are advanced into the ascending aorta. The tip of the catheter may also be placed in the right or left subclavian arteries, depending on the location and angulation of the coarcted segment. The catheter is left in place, and the guide wire is removed and replaced with either an extra-stiff exchange-length 0.035-in Amplatz or a super-stiff, short tip, Amplatz guide wire. The catheter is then removed.

If the approach to the lesion is tortuous or difficult to reach, the authors select a 0.038-in super-stiff Amplatz wire. An appropriate-sized long blue Cook sheath with a multipurpose curve and a radiopaque marker at the tip is introduced over the stiff wire. Once the tip of the sheath is past the site intended to be stented, the dilator is removed and the sheath flushed. Sometimes, the dilator has to be withdrawn slightly to position the tip of the sheath at the desired location.

The selection of the sheath diameter obviously depends on the size of the stent delivery catheter. The authors have always attempted to select a balloon delivery system that would allow the smallest possible sheath diameter. Initially, when other workers were using Meditech PE-MT balloon catheters, which required 11F sheaths, the authors were using Olbert balloon catheters, which can be introduced through 8F or 9F sheaths for mounting the stent. Subsequently, the authors have used Bridge stents, which can also be delivered via 8F or 9F sheaths. [60] Most recently, the authors used IntraStent DoubleStrut stents and Palmaz Genesis. [116] The latter stents are mounted on balloon-in-balloon (BIB) catheters. The size of the sheath used is 1F larger than the sheath size needed for the BIB catheter.

The selected stent is hand crimped onto a BIB catheter; the authors use a sterile umbilical tape to further crimp the stent onto the balloon.

The balloon catheter, with the stent mounted on it, is advanced over the stiff guide wire but within the sheath and positioned across the coarctation segment. The tip of the sheath is withdrawn distal to the aortic coarctation based on bony landmarks. Contrast is also injected via the side arm of the blue Cook sheath, and the position of the stent is adjusted as necessary. Some cardiologists place catheters into the ascending aorta via trans-septal route or from radial artery for angiography during stent placement. [120] Although this may provide better visualization, the authors do not routinely recommend it to avoid additional time in the catheterization laboratory and morbidity associated with such additional procedures.

In cases in which the BIB catheter is used, the inner balloon is inflated at the manufacturer's recommended pressure and the position of the stent adjusted, if needed, followed by inflation of the outer balloon, thus implanting the stent. The balloon catheter is then advanced slightly, centering the balloon across the proximal end of the stent, and the outer balloon is re-inflated to ensure apposition of the stent against the vessel walls. The balloon catheter is then centered over the distal end of the stent. This is performed by advancing the tip of the sheath over the deflated balloon into the stent to prevent inadvertent displacement of the stent. [121] The outer balloon is then re-inflated to ensure apposition of the distal stent against the vessel walls.

If the outer balloon diameter is not as large as the desired diameter of the stent, additional balloon expansion with larger diameter balloons is performed. The author always tries to avoid this step by using an outer balloon of the BIB catheter at the desired diameter. Following the removal of the balloon catheter, a multitrack catheter [122] is positioned over the wire, and pressure pullback tracings and angiography are performed to assess the results of stent implantation.

The effect of heparin is not reversed, and no additional doses of heparin are administered. Intravenous cefazolin 25 mg/kg/dose (maximum of 1 g) is started in the catheterization laboratory, and 2 additional doses are administered at 6- to 8-hour intervals. Aspirin in platelet-inhibiting doses (5-10 mg/kg/d) is started on the day following the procedure and continued for 6 weeks. Use of heparin overnight on the day of procedure and more potent platelet-inhibiting drugs or anticoagulation with warfarin (Coumadin) have been undertaken in the past. At present, the data do not indicate the need for intensive anticoagulation. Aspirin alone appears to suffice. However, more potent platelet-inhibiting drugs, such as clopidogrel, may be used in adults.

To avoid potential balloon rupture, the tip of the guide wire is placed in the right subclavian artery instead of the ascending aorta, which is the usual practice for balloon angioplasty. Try not to position the stent across the origins of left common carotid artery and left subclavian artery. However, on occasion, avoiding the subclavian artery is impossible. In such situations, the authors have carefully traversed the stent cells (in between the struts) with a soft guide wire followed by a multi-A2 catheter. The stent cell is then dilated with an angioplasty balloon of a diameter equal to that of the proximal left subclavian artery; uncompromised flow to the left subclavian artery was found in these patients. Predilation of the coarcted segment with balloon angioplasty prior to stenting is no longer recommended.


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