INTRAVASCULAR ULTRASOUND ASSESSMENT OF THE MECHANISMS AND PREDICTORS OF RESTENOSIS FOLLOWING CORONARY ANGIOPLASTY

Restenosis occurs after 30% to 50% of transcatheter coronary procedure s; its mechanisms remain incompletely understood. Intravascular ultras ound (IVUS) studies were analyzed in 360 nonstented native coronary ar tery lesions in which follow-up quantitative angiographic and/or IVUS data was available. Pre-intervention, post-intervention, and followup, the external elastic membrane (EEM) and lumen cross-sectional areas ( CSA) were measured; plaque+media (P+M=EEM - lumen CSA), and cross-sect ional narrowing (CSN=P+M/EEM CSA) were calculated. The anatomic slice selected for serial analysis had an axial location within the lesion a t the smallest follow-up lumen CSA. At follow-up, 73% of the decrease in lumen CSA was due to a decrease in EEM CSA; 27% was due to an incre ase in P+M CSA. The change in lumen CSA correlated more strongly with the change in EEM CSA than with the change in P+M CSA. The change in E EM CSA was bidirectional; 47 lesions (22%) showed an increase in EEM C SA. Despite a greater increase in P+M CSA, lesions exhibiting an incre ase in EEM CSA had (1) no change in lumen CSA, (2) decreased restenosi s, and (3) a 49% frequency of late lumen gain. The independent clinica l, angiographic, and IVUS predictors of angiographic restenosis (great er than or equal to 50% diameter stenosis at follow-up) were the IVUS reference lumen CSA, angiographic pre-intervention diameter stenosis, and post-intervention IVUS CSN. Restenosis appeared to be determined p rimarily by the direction and magnitude of the change in EEM CSA. An i ncrease in EEM CSA was adaptive while a decrease in EEM CSA contribute d to restenosis. The most powerful predictor of restenosis was the IVU S post-procedural CSN. The importance of the post-procedural CSN was r elated to the change in EEM CSA as a mechanism of restenosis.