Intracoronary Radiation Post PTCA Prevents Late Arterial Constriction

Vascular constriction post PTCA is a major component in the mechanism of restenosis following intervention. Ionizing radiation demonstrated reduction of neointima formation after injury in animal models and lowered the restenosis rates in pilot clinical studies. To determine the effect of intracoronary radiation therapy on vascular remodeling, angiograms from two radiation trials were analyzed by QCA methods. Patients in these trials had de novo lesions and were treated with balloon angioplasty followed by either beta or gamma radiation. All patients were studied angiographically at 6 months; patients with total occlusion at the treated artery were excluded from the analysis. In the gamma trial, 192-Iridium was utilized in 14 patients (15 lesions) with doses between 20-25 Gy. In the beta trial, 90-Sr/Y was utilized in 17 patients (17 lesions) with doses between 12-16 Gy. The QCA analysis from these studies demonstrated negative late loss and late loss index at six months for patients from the beta (-0.02 ± 0.3) and the gamma (-0.19 ± 0. 3) study. The effect of positive remodeling was maintained at 24 months, -0.16 ± 0.4 in the gamma group. Larger MLD at follow-up compared to the immediate post MLD were demonstrated in 50% of the patients from both studies. Thus, intracoronary radiation resulted in lower late loss and late loss index rates than previously reported following balloon angioplasty alone suggesting a positive vascular remodeling effect of intracoronary radiation.