QUANTITATIVE-ANALYSIS OF ELASTIC RECOIL AFTER BALLOON ANGIOPLASTY AND AFTER INTRACORONARY IMPLANTATION OF BALLOON-EXPANDABLE PALMAZ-SCHATZ STENTS

Objectives. The purpose of this study was to measure elastic recoil from sequential angiograms after balloon angioplasty and after implantation of a balloon-expandable Palmaz-Schatz stent in the same patient, and to compare the results with the late angiographic outcome. Background. The immediate result of coronary balloon angioplasty is influenced by plastic deformation, primarily of the atherosclerotic plaque, and by elastic recoil, primarily of the less or nondiseased vessel circumference. Methods. The extent of elastic recoil was measured quantitatively as the difference between maximal balloon size and the resulting vessel diameter or cross-sectional area. Results. Analysis was performed in 60 patients who received a single stent for late restenosis after initially successful coronary balloon angioplasty. Minimal lumen diameter (minimal cross-sectional area) was 0.98 +/- 0.43 mm (0.97 +/- 0.67 mm2) before balloon angioplasty, 2.06 +/- 0.36 mm (3.68 +/- 1.17 mm2) after angioplasty (both p < 0.001 vs. values before angioplasty) and 2.98 +/- 0.26 mm (7.12 +/- 1.28 mm2) after stenting (both p < 0.001 vs. postangioplasty results). No significant changes in vessel reference diameters or areas were measured. Mean balloon/artery ratios were similar in both procedures, ranging from 0.93 to 0.96. The calculated mean elastic recoil was 0.98 +/- 0.50 mm in diameter (31%) and 3.67 +/- 2.05 mm2 in area (48%) after balloon angioplasty compared with 0.10 +/- 0.07 mm (3.5%) and 0.38 +/-0.36 mm2 (5.1%) after stenting. Increasing balloon sizes induced increased vessel stretch, which was followed by increased elastic recoil in the angioplasty group in contrast to the stenting group. Short, noncalcified and eccentric lesions tend to be associated with increased recoil after balloon angioplasty. Overdilation or under-dilation in one of the procedures, changes in postprocedural vasomotion or postprocedural thrombus formation was not responsible for this outcome. After 6 months mean minimal lumen diameter was 2.39 +/- 0.58 mm, suggesting a mean hyperplasia of 0.59 +/- 0.51 mm. Twelve patients (20%) had a follow-up diameter thal was equal to or less than the mean postangioplasty result and eight patients (14%) had a diameter stenosis of >50%. Conclusions. The implantation of a Palmaz-Schatz stent almost completely eliminates the decrease in vessel dimensions caused by elastic recoil and therefore diminishes the impact of hyperplasia and reduces the rate of restenosis.