Thoracic Endovascular Aortic Repair (TEVAR) Balloons

Introduction

Balloon catheters have two principal applications in peripheral endoluminal procedures. Therapeutic or angioplasty ballooning is the forceful inflation of a balloon to dilate stenotic/occlusive lesions in a vessel. This is accomplished using noncompliant balloons, constructed of material that resists deformation when subjected to pressure; the more noncompliant (i.e. stiffer) the balloon material, the greater the dilating force that can be produced. By contrast, molding or occlusion ballooning is a less forceful balloon inflation to ensure endograft expansion, placement, and fixation. This is done using larger compliant balloons and a more gentle inflation. These balloons are also used to stop blood flow in medium or large vessels as needed in certain vascular procedures.

Besides balloon type, important considerations when choosing any balloon catheter are: balloon material, catheter length and diameter, inflated balloon length and diameter, and balloon shoulder length.

Materials

Angioplasty balloons are composed of polyethylene, polyethylene terephthalate (Dacron), nylon, or other low-compliance polymers. Burst pressure, which is the specific inflation pressure at which 1% of tested balloons burst, is rated by the manufacturer. Most polyethylene balloons are rated to 10-12 atm, whereas Dacron and other polyester balloons are rated up to 15 atm. The Blue Max Balloon (Boston Scientific Corp.) and similar products are notable for their reinforced high-pressure polymer construction and ability to be pressurized to 20 atm. Occlusion balloons are manufactured of compliant polymers such as polyurethane, latex, or silicone. Burst pressures in occlusion balloons (usually ~ 5 atm) are of less consequence because these balloons are not meant to exert large amounts of force, making inflation to high pressures unnecessary.

Catheters Length & Diameter

Balloon catheters range from 40 cm to 150 cm in length. For ease of control, the shortest length that can reach the intended segment is customarily used. Standard angioplasty balloons (corresponding to inflation diameter of 3-7 mm) are usually delivered in 5F angioplasty catheters. Large diameter or high-pressure angioplasty balloons, such as those used in iliac vessels, often require 5.8-7F catheters. Large aortic occlusion balloons are delivered in 12-20F balloon catheters. These catheters are often inserted through an appropriate sheath after delivery of larger profile endograft systems.

Balloon Length & Diameter (With Author Preferences)

Angioplasty balloon lengths may range from 1.5 cm to 10 cm, and a length is chosen, ideally, to dilate the stenotic area with a single inflation. When this is not possible, sequential overlapping dilatations are performed. The inflation diameter of a balloon for angioplasty is selected at an oversized scale, generally 110-120% of the calculated “normal” vessel diameter. For dilatation of iliac access vessels in (T)EVAR, we prefer the Ultrathin Diamond Balloon Dilatation Catheter (Boston Scientific Corp.). The 8 cm length of this balloon is valuable in treating the often extensive calcification of the iliac vessels. Additionally, the diameter of the inflated balloon reaches 8 mm (corresponding to 24F compatibility), while being delivered in a low-profile 5.8F catheter.

The aortic occlusion balloons that we use are generally 3-5 cm in length and assume a near-spherical configuration when fully inflated (i.e. have an exceedingly short shoulder length—see next section). In a non-stenotic aorta, inflation to 40 mm diameter is obligatory for these balloons to be effective. The Reliant Stent Graft Balloon, designed to be used with the AneuRx AAAdvantage Stent Graft System (Medtronic, Inc.), is an excellent molding balloon for endografts. This very compliant balloon can be inflated up to 46 mm in diameter (the largest of any profile balloon to our knowledge) and is delivered in a 12F catheter. The Coda Balloon (Cook, Inc.) is also very useful in endograft molding and aortic occlusion. This balloon is composed of a semi-compliant material, which facilitates the rapid inflation and deflation that is advantageous when occluding the aorta. The unique Tri-Lobe Balloon (W. L. Gore & Associates, Inc.) provides a dilatation force on three axes (separated by 120 degrees) in the aorta without complete blockage of blood flow. This reduces the windsock effect of the occluding balloon to the stent graft.

Balloon Shoulder Length

Radiopaque markers designate the central balloon segment that attains the desired inflation diameter. The shoulder length of a balloon is the tapered balloon segment from the radiopaque marker to the outermost extent of the balloon. Shoulder length becomes especially important when ballooning near regions where dilatation is contraindicated, such as branch points or lesions.

Conclusion

The angioplasty balloons discussed here represent a small sample of products routinely used for dilatation of iliac vessels as well as the aorta, in conjunction with endoluminal procedures of the aorta. Similarly, the occlusion balloons mentioned are only some of those used for aortic endografting. The numerous other applications of peripheral ballooning carry their own abundant selections of products.

References

1. Schneider PA. Endovascular Skills, 3rd Ed. New York: Informa 2009.
2. Rutherford RB. Rutherford Vascular Surgery, 6th Ed. Philadelphia: Elsevier Saunders, 2005.
3. Casserly IP, Sacher R, Yadav JS, eds. Manual of Peripheral Vascular Intervention. Philadelphia: Lippincott Williams and Wilkins, 2005.
4. Moore WS. Vascular and Endovascular Surgery: A Comprehensive Review, 7th Ed. Philadelphia: Elsevier Saunders, 2006.
5. White RA, Fogarty, TJ, eds. Peripheral Endovascular Interventions, 2nd Ed. New York: Springer-Verlag, 1999.