Residual plaque burden, delivered dose, and tissue composition predict 6-month outcome after balloon angioplasty and beta-radiation therapy

Background-Inhomogeneity of dose distribution and anatomic aspects of the a therosclerotic plaque may influence the outcome of irradiated lesions after balloon angioplasty (BA). We evaluated the influence of delivered dose and morphological characteristics of coronary stenoses treated with beta-radia tion after BA. Methods and Results-Eighteen consecutive patients treated according to the Beta Energy Restenosis Trial 1.5 were included in the study. The site of an gioplasty was irradiated with the use of a beta-emitting Sr-90/Y-90 source. With the side branches used as anatomic landmarks, the irradiated area was identified and volumetric assessment was performed by 3D intracoronary ult rasound imaging after treatment and at 6 months. The type of tissue, the pr esence of dissection, and the vessel volumes were assessed every 2 mm withi n the irradiated area. The minimal dose absorbed by 90% of the adventitial volume (D(v90)Adv) was calculated in each 2-mm segment. Diffuse calcified s ubsegments and those containing side branches were excluded. Two hundred si x coronary subsegments were studied. Or those, 55 were defined as soft, 129 as hard, and 22 as normal/intimal thickening. Plaque volume showed less in crease in hard segments as compared with soft and normal/intimal thickening segments (P<0.0001). D(v90)Adv was associated with plaque volume at follow -up after a polynomial equation with linear and nonlinear components (r=0.7 1; P=0.0001). The multivariate regression analysis identified the independe nt predictors of the plaque volume at follow-up: plaque volume after treatm ent, D(v90)Adv, and type of plaque. Conclusions-Residual plaque burden, delivered dose, and tissue composition play a fundamental role in the volumetric outcome at 6-month follow-up afte r beta-radiation therapy and BA.