Three-dimensional intravascular ultrasound assessment of noninjured edges of beta-irradiated coronary segments

Background-The "edge effect," late lumen loss at the margins of the treated segment, has become an important issue in the field of coronary brachyther apy. The aim of the present study was to assess the edge effect in noninjur ed margins adjacent to the irradiated segments after catheter-based intraco ronary beta-irradiation. Methods and Results-Fifty-three vessels were assessed by means of 3-dimensi onal intravascular ultrasound after the procedure and at 6- to 8-month foll ow-up. Fourteen Vessels (placebo group) did not receive radiation (sham sou rce), whereas 39 vessels were irradiated. in the irradiated group, 48 edges (5 mm in length) were identified as noninjured, whereas 18 noninjured edge s were selected in the placebo group. We compared the volumetric intravascu lar ultrasound measurements of the noninjured edges of the irradiated vesse ls with the fully irradiated nonstented segments (IRS, n=27) (26-mm segment s received the prescribed 100% isodose) and the noninjured edges of the ves sels of the placebo patients. The lumen decreased (6 mm(3)) in the noninjur ed edges of the irradiated vessels at follow-up (P=0.001). We observed a si milar increase in plaque volume in all segments: noninjured edges of the ir radiated group (19.6%), noninjured edges of the placebo group (21.5%), and IRS (21.0%). The total vessel volume increased in the IRS in the 3 groups. No edge segment was subject to repeat revascularization. Conclusions-The edge effect occurs in the noninjured margins of radiation s ource train in both irradiated and placebo patients. Thus, low-dose radiati on may not play an important role in this phenomenon, whereas nonmeasurable device injury may be considered a plausible alternative explanation.