INTRAVASCULAR ULTRASOUND AFTER LOW AND HIGH INFLATION PRESSURE CORONARY-ARTERY STENT IMPLANTATION

Objectives. We sought to characterize the differences seen after low or high pressure coronary artery stent deployment as assessed by intravascular ultrasound. Background. Until 1992, the success of stent deployment was assessed by angiographic criteria only, but in 1993 the procedure was expanded to include postprocedural single-use intravascular ultrasound imaging. Ultrasound criteria for successful stent deployment were 1) symmetry, 2) minimal lumen diameter >3.0 mm, 3) no echo free spaces between the stent and the vessel, and 4) no uncovered dissections. Methods. We used mechanical 4.8F or 3.5F 20- or 30-MHz monorail single-use intravascular ultrasound catheters. Results. Fifty-two patients were included, 28 treated in 1991 and 1992 (group A) and 24 treated in 1993 or 1994 (group B); 87% of patients underwent elective stent implantation. The number of echocardiographic studies per patient increased from 1 +/- 0.1 (mean +/- SD) in group A to 2.0 +/- 0.85 in group B. Mean maximal balloon size increased from 3.3 +/- 0.33 to 3.73 +/- 0.24 mm and maximal inflation pressure from 6.9 +/- 1.1 to 15.8 +/- 2.4 bar (p < 0.001). The eccentricity index was 0.915 +/- 0.04 in group B versus 0.87 +/- 0.05 in group A. Minimal lumen diameter measured by echocardiography increased from 2.55 +/- 0.41 mm in group A to 3.14 +/- 0.37 mm in group B. The final mean values per cross-sectional area as a percent of calculated balloon area were similar in group A (67.5 +/- 23%) and group B (66.5 +/- 22.9%). No major acute complications occurred in either group; subacute thrombosis developed in two patients, both in group A. Conclusions. Intravascular ultrasound data confirm that high pressure stent deployment leads to increased minimal lumen area. Despite high pressure stent deployment, homogeneous stent geometry and optimal stent expansion were not observed in all patients.