Intraluminal radiation following coronary balloon angioplasty

Intraluminal radiation after balloon angioplasty to prevent restenosis has been studied extensively in the animal models especially using the procine animal most similar to that of the human. Approximately 400,000 angioplasties will be performed in the United States in 1996. Between 30 and 45% of these will restenose within 3-6 months. After a second balloon angioplasty with stent placement up to 35% will also restenose. Pharmacologic interventions have not proven to be successful at this time. What we propose is to give intraluminal radiation to the part of the vessel that has been dilated by balloon angioplasty with or without stent placement. This will be performed using an iridium ribbon and will be secured in place shortly after the angioplasty procedure to give approximately 8-25 Gy at 1 mm depth within the vessel wall. This dosage was based on experimental data accrued and published over the past 2 years. The procedure will be performed in the angioplasty suite and after standard balloon angioplasty has been performed using double blind criteria, the patient will be chosen and known only to radiation safety officers who will assist in implantation with radiation or who will have dummy seeds placed. The ribbon with the iridium seeds will stay in the coronary vessel for approximately 20-45 minutes. The procedure will be performed after standard balloon angioplasty with intraluminal ultrasound to calculate dose. Under fluoroscopic guidance the iridium ribbon will be advanced to coincide with .5 cm beyond the coronary vessel lesion, if possible in either direction to give a .5 cm treatment area beyond the angioplasty site. The iridium ribbon will remain in place to allot enough time to give the vessel wall between 8 and 25 Gy at which time the iridium ribbon will be removed with the infusion catheter. (The iridium ribbon will remain in the infusion catheter throughout the procedure.) The iridium ribbon used will contain anywhere from 8 mg radium equivalent to 20 mg radium equivalents per seed, 5 or 9 seeds per ribbon. The ribbon itself is nylon with a sealed end so that the seeds cannot migrate. We may also enclose a catheter around the ribbons so that the ribbons are in a sealed tube. This will further prevent any seed migration. Radiation to prevent cellular proliferation and matrix production has been utilized for over 80 yrs. This has been a proven treatment modality to prevent keloid formation, prevents normal fibroblasts from transforming into proliferative cells producing an exaggerated scar and heterotopic bone formation, preventing osteoblasts from transforming into migrating and proliferative cells. In the formation of neointima in restenosis, smooth muscle cells are transformed into migratory and proliferative cells as in heterotopic bone and keloid formation. In summary, intraluminal radiation after balloon angioplasty has been successful in the animal model. Dosages between 8 and 25 Gy are within the range needed to prevent this restenosis from recurring. We will conduct a double blinded study to assess radiationʹs impact on preventing restenosis.