Geographical miss during centered intracoronary beta‐radiation with 90Yttrium: incidence and implications for recurrence rates after vascular brachytherapy for de novo lesions

OBJECTIVES: The authors sought to determine the incidence and causes of geographical miss (GM) and evaluate its impact on edge restenosis after ‘primary’, centered, intracoronary β‐radiation therapy. BACKGROUND: Edge restenosis is a limitation of intracoronary β‐radiation therapy. GM occurs when the radiation source does not fully cover the injured segment and may account for this phenomenon. METHODS: One hundred and eighty‐one patients enrolled in the Dose‐Finding study were retrospectively analyzed. The patients were randomized to receive 9, 12, 15 or 18 Gy at 1 mm tissue depth. Using quantitative coronary angiography the effective irradiated segment (EIRS) and both edges were studied prior to and after intervention, and at six‐month follow‐up. GM was defined as a situation where the effective radiation source length (24 mm) did not fully cover the injured segment. The edges of the EIRS that were injured during the procedure constituted the GM edges. A greater than 50% diameter stenosis at follow‐up was considered significant. GM was determined by the simultaneous, electrocardiographically matched, side‐by‐side projection of the source and balloons in place, in identical projections surrounded by contrast. RESULTS: In 16% of patients GM was noninterpretable owing to inadequate filming. GM constituted 21.1% of the interpretable edges and 40.1% of the interpretable vessels analyzed. The occurrence of restenosis in the EIRS and the analyzed vessel segment (VS) was similar between procedures with and without GM. In vessels with GM, restenosis was significantly increased from the EIRS to the VS (from 8.77% to 21%, p = 0.05) as opposed to non‐GM vessels (from 11.9% to 19%, p = 0.6). GM tended to be associated with a greater incidence of significant stenosis at the edges of the EIRS (8.3% versus 4.0%, p = 0.15) compared with individuals with >50 % stenosis but no GM. This effect was more prominent at the distal edge. The relation of GM and edge restenosis was independent of dosage. CONCLUSIONS: Since GM does not affect the incidence of restenosis in the EIRS, restenosis in this segment should be considered a treatment failure, probably due to inadequate dosage. GM is related to significant increase in restenosis from the EIRS to the VS. GM tends to be associated with restenosis at the edges of the EIRS. This is a local phenomenon, which is independent of dosage and which has a specific pathophysiology (combination of injury and low‐dose radiation). If GM can be eliminated, the results of vascular brachytherapy will be improved. (Int J Cardiovasc Intervent 2003; 5: 181–189)