ADDITIONAL LUMINAL AREA GAIN BY INTRAVASCULAR ULTRASOUND GUIDANCE AFTER CORONARY STENT IMPLANTATION WITH HIGH INFLATION PRESSURE

Aims: Studies by intravascular ultrasound demonstrated inadequate expa nsion in a large number of stents, which lead to the increase of infla tion pressures for stenting. The present study examined whether routin e use of high-pressure inflation would be sufficient for an optimum st ent expansion without sonographic guidance. Methods and results: Two t ypes of single coronary stents (Palmaz-Schatz in 54, and Wiktor in 25) were implanted with inflation pressures of 16-20 atm in 79 nonocclusi ve coronary lesions. IVUS before stenting was used in 78% to select th e adequate stent size. Intravascular ultrasound after stenting was use d to assess the minimum stent area and diameter, the reference areas, and the strut apposition to the vessel wall. The difference between th e area of the expanding balloon and the stent area was calculated as t he luminal deficit of the stent. Completeness of stent expansion requi red full strut apposition and lesion coverage, and a minimum stent are a that was larger than the distal reference, and larger than 60% of th e proximal reference. Intravascular ultrasound before stenting lead to an increase of the stent size in 47%. After high-pressure expansion, even with the optimized balloon size, 8% of stents had struts protrudi ng into the lumen. The stent area (6.87 +/- 1.93 mm(2)) was significan tly smaller than both the proximal (9.59 +/- 2.91 mm(2); p<0.001) and distal reference area (8.23 +/- 3.03 mm(2); p<0.001). The criteria for complete expansion were met in 48%. The expansion with a larger high- pressure balloon in 25 stents lead to an increase of the stent area by 19% (8.19 +/- 2.24; p<0.001), and full stent apposition in all cases. The criteria of stent expansion were met in 82%. A wide range of the luminal deficit upto 48% was observed, which was not related to sonogr aphic lesion characteristics, except in lesions with complete circumfe rential calcifications. The different stent designs were characterized by a slightly lower luminal deficit in slotted-tube stents (23 +/- 13 % vs. 28 +/- 12%; p = 0.11) and a better index of stent symmetry as co mpared with the coil stent (0.87 +/- 0.08 vs. 0.82 +/- 0.09; p<0.05). Conclusion: Routine use of high-pressure stent expansion did not lead to a sufficient stent expansion, even when the initial stent size had been guided by intravascular ultrasound. Further stent dilatation with larger balloons under ultrasound guidance would be required to optimi ze the luminal area gain.