Mechanisms of Residual Lumen Stenosis After High-Pressure Stent Implantation

Abstract

Background—Intravascular ultrasound (IVUS) studies have demonstrated that stents are frequently suboptimally expanded despite the use of high pressures for deployment. The purpose of this study was to identify the mechanisms responsible for such residual lumen stenosis.Methods and Results—Fifty-seven lesions from 50 patients treated with high-pressure (median±interquartile range, 14±2 atm) elective (44 de novo, 13 restenotic lesions) stenting were prospectively studied (29 Wiktor, Medtronic; 28 Palmaz-Schatz, Cordis Corp). Balloon subexpansion was calculated as the difference between maximal and minimal balloon cross-sectional areas at peak pressure measured by automatic edge detection; elastic recoil was calculated as the difference between minimal measured balloon size and IVUS-derived minimal lumen area within the stent. Angiographic residual diameter stenosis was 10±13% (reference diameter, 3.1±0.7 mm; balloon to artery ratio, 1.12±0.23) and IVUS-derived stent expansion was 80±28%. However, although balloon nominal size was 9.6±1.3 mm2and maximal balloon size measured inside the coronary lumen was 12.5±3.2 mm2, final stent minimal lumen area was only 7.1±2.2 mm2. Balloon subexpansion of 4.0±1.8 mm2(33%) and elastic recoil of 1.6±2.3 mm2(20%) (bothP<0.0001) were the two mechanisms responsible for residual luminal stenosis. Wiktor stent and peak inflation pressure correlated with balloon subexpansion, whereas Wiktor stent, de novo lesion, and minimal lumen area at baseline correlated with elastic recoil.Conclusions—Despite high-pressure deployment, lumen dimensions after stenting are only 57% of maximal achievable. Inadequate balloon expansion and elastic recoil are responsible for residual lumen stenosis, suggesting that plaque characteristics and stent resistance deserve further investigation.