1018-52 Volumetric Intravascular Ultrasound Volumetric Analysis Shows that Small Stent Size and Intimal Hyperplasia Contribute to Restenosis

To explore the mechanisms and patterns of stent restenosis, we performed volumetric intravascular ultrasound analysis (IVUS) in 60 tubular-slotted stents a mean of 8 months after implantation. Motorized transducer pullback (@ 0.5 mmls within a stationary imaging sheath) permitted measurement of stent and lumen cross-sectional areas in 1 mm axial increments and calculation of stent, lumen, and neointimal hyperplasia (IH = stent–lumen) volumes using Simpson's Rule. Lumen areas were normalized for a reference lumen cross-sectional area to calculate a % area stenosis (AS) for each cross-section. Restenosis was defined as a quantitative angiographic % diameter stenosis ≥50 or an IVUS %AS ≥75.sRestenosis (N=6)No Restenosis (N=20)PStent volume (mm3)120±41147±430.016Lumen volume (mm3)62±28118±42<0.001IH volume (mm3)58±3629±18<0.001We then defined diffuse and focal patterns of restenosis: (1) diffuse=more than 50% of the stent length having a %AS ≥ 75 and (2) focal=less than 50% of the stent length having a %AS ≥75.Diffuse (N=6)Focal (N=20)PStent volume (mm3)120±31120±44NSLumen volume (mm3)36±1570±26<0.005IH volume (mm3)84±3050±34<0.05In pts with focal in-stent restenosis, the region of greatest %AS was at the central articulation in 9 (45%), at the stent margins in 6 (30%), and within a stent segment in 5 (25%).We Conclude(1) IVUS imaging with automated transducer pullback allows detailed volumetric analysis of in-stent restenosis. (2) In-stent restenosis is due to a combination of reduced stent volume and greater IH. (3) Diffuse in-stent restenosis is seen in less than 1/3 of restenotic stents and is associated with more aggressive neointimal growth than the more common pattern of focal restenosis. Further studies are required to determine if differing patterns of in-stent restenosis are associated with subsequent clinical outcomes