Study Predictors Of Suboptimal Stent Deployment: Clinical, Angiographic And Intravascular Ultrasound

Abstract

Background: Although Intravascula:: Ultrasound (IVUS) allows more accurate assessment of proper stent e>:pansion, it is not readily available for routine application, There is. need to define the relative value of quantitative coronary angiography {QCAl in the evaluation of• optimal sc:ent deployment (OSD). Objectives: To compare QCA with ! 1/US imaging in the evaluation of optimal stent expansion using high pressu::e {:•:PJ inflation and to determine whether models relating QCA(Q) and IVUS(I) measurements can be used to predict the actual IVUS parameters. These models can then be used to perfo::::m optimal stent deployment guided only by QC?. data. Methods We recorded simultaneous QCA and IVUS measurements in 78 consecutive pts. 1-:ho had 90 stents deployed at hig:: pressure. Data in total casES (Mean SD): IRLD 3.4 0.39 mm, QRLD 3.1 .:!:_ 0.44 mm, IRVD .3 0.41 rn.;r., stent size 3.4 .:!:_ 0.31 mm, inflation presst:re 18.3 2:. 1.6 atm. Stent expansion index (Exp Ind) as calculated as stent minimal lumen diamete::::(MLD) /average reference lumen diameter(RLD) %.Angiog::::aphic evidence fo:::: OSD included the appearance of step-up or step-down and instent residual diameter stenosis < 20%. IVUS criteria for OSD were ste::.t Exp Ind (stent minimal lumen area (MLAJ /average reference lumen areal ;,o in addition to complete ap::;osition of the stent struts againest the vessel •,1all over its entiro: length. Results: Patients were randomly divided into a training group (Gpi,45 stentsJ and a test group (Gpii, 115 stentsl. The following modo:ls were derived in Gp! and tested in Gpii.: 1) In Gpi, QRLD correlated -.•ith I LD, r '"' 0. 7 5, p<O. 0005. The regression equa.t.ion: calculated (Cl RLD "'1. 52+0. 6 (QRLD) was applied to derive CRLD in Gpii pts. 2) In Gp!, an index relating RLD to RVO was derived as CRLD/IRVD:mean"' 0.79, {95% CI 0.77,0.81) .This value was used to obtain a CRVD in Gpii by dividing CRLD by 0. 79 in each case. From (1) and {2), a proper stent size at a given inflation pressure can be selected to fit between the calculated RLD and RVD. 3) In Gpi, ISMLA correlated with QSMLA, r = 0,49, p = 0.002. The regression equation CSMLA = 5.16 + 0.49 (QSMLA) was used to derive a calculated SMLA in Gpii pts. Model 3 can be used to assess the SMLF-. after stent deployment. Paired t-test showed no significant difference between calculated and IVUS measurements obtained in the test group (t =1.45, p = 0.15 for RLD, t -= 1.03, p = 0.31 for RVD, t = 0.26, p = 0. 79 for SMLA). The individual differences ranged from - 0.5 to + 0.5 mm for RLD in 98of cases and for RVD in 89% of cases. The differences ranged from -1.0 to+ 1.0 mm2 for SMLA in 77% of cases. As regards LP versus HP stent deployment as a•ssessed •by QCA and IVUS, our results are shown in table.