Restenosis withintubularSION stentsissecondaryto intimalhyperplasiaand is usuallytreatedwithpercutWWOUS tmnsluminal coronaryangioplasty(PTCA).Sequential intravascular ultrasound(IVUS)wasueed to assess the mechanisms and resultsof PTCAfor in-stent restenosis. Sixty-fourrestenoticPalmaz-Schatz stents werestudiedby IVUSimagingbeforeand afterPTCA. IVUSmeasurements of stentand lumencross-seclkmcd areas(CSA5)at 5 segments(proximaland distalstent edges,proximalanddistalstentbodies, andthecentral articulation) wereusedtocalculate intimalhyperplasia CSA(stent– lumenCSA).Theresultsof the5 segments wereihenaveraged.Meanand minimumCSASwere comparedbefareand afterPTCA.Quantitativeangiographicmeasurements showeda minimalumendiameterincreasefrom1.05f 0.63 mm(mean& 1SD)be,fore interventionto 2.77 * 0.51 mm afterPTCA(p <0.0001). Conversely, thediameter stenosis decrased from63 x 19%to 18 f 12%(p <0.0001). IVUSmeasummenkshoweda minimumlumenC5Aincrease from 2.3~ 1.3mm2ta6.1~ 2.2mm2(p <0.0001)asa red ofanincreased minimumdentC5A(7.2k 2.4mm2to8.7 ~ 2.6mm2,p <0.0001)anda decreased intirnal hyper plasiaCSAwithinhe stent(4.9~ 2.2mm2to2.7 f 2.0 mm2,p <0.0001’).Of thetotalmeanlumenenlargement, 56 z 28%WOStheresult ofadditkmIstent expansion and 44 ~ ~O~s thew~ofa fi~ in*fimg[ fire.