Frequency and Severity of Plaque Prolapse Within Cypher and Taxus Stents as Determined by Sequential Intravascular Ultrasound Analysis

Abstract

We used intravascular ultrasound to evaluate the incidence, characteristics, and clinical sequel of plaque prolapse within drug-eluting stents. The influence of stent design on plaque prolapse has not been studied. Drug-eluting stents were serially expanded, first at 14 atm and then at 20 atm, with intravascular ultrasound imaging after each inflation. The stent, lumen, and maximum plaque prolapse areas were measured. The residual lumen area and percentage of plaque prolapse burden (maximum plaque prolapse area/stent area) were calculated. Plaque prolapse was divided into grades 1 (<5%), 2 (5% to 10%), and 3 (10% to 20%). Eighty patients (83 lesions, 41 Cypher and 42 Taxus Express stents) were studied. The incidence of plaque prolapse was 41% (17 of 41 lesions) with the Cypher stents versus 24% (10 of 41 lesions) with the Taxus stents after 14 atm (p = 0.096) and 35% (14 of 40) in Cypher stents versus 17.8% (5 of 28) in Taxus stents after 20 atm (p = 0.17). However, the maximum plaque prolapse area was never >20% of the stent area. The frequency and amount of plaque prolapse neither increased nor decreased at higher (20 atm) inflation pressures. Lesions with prolapse were longer (p = 0.004), with a larger external elastic membrane area and greater plaque burden (each p <0.0001) and a larger remodeling index (p = 0.013). Conversely, nonprolapsed plaques had a higher incidence of superficial calcium (p = 0.001). Creatinine kinase-MB elevation was higher with plaque prolapse, and the magnitude of creatinine kinase-MB elevation correlated with the extent of plaque prolapse (r = 0.664, p = 0.002). Multiple logistic regression analysis indicated that a longer lesion length (p = 0.012), and smaller minimal luminal area (p = 0.031) had higher risks of plaque prolapse. In conclusion, plaque prolapse was frequently observed in Cypher and Taxus stents. However, sequential intravascular ultrasound imaging showed that the frequency and amount of plaque prolapse were neither increased nor decreased by additional higher pressure inflations.