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A Novel Method of Brachytherapy Using Local Delivery of 99mTc–HMPAO for Coronary Stent Restenosis

Background Restenosis after percutaneous coronary intervention (PCI) is a matter that still remains to be resolved. Herein, the inhibitory effect of locally delivered 99mTc–HMPAO (hexamethyl propylene amine oxime) on neointimal hyperplasia after coronary stenting was examined in a pocine model, and its safety and efficacy observed in patients with coronary stent restenosis. Methods After a stent overdilation injury, local radioisotope delivery using 99mTc–HMPAO was applied to one coronary artery (Group I) and control therapy to another (Group II) in each of 10 pigs. Follow-up coronary angiogram (CAG) and histopathologic assessment were performed 4 weeks after stenting. Eleven patients (10 males and one female, 62.4±5.7 years of age) underwent local administration of 30 mCi/2 mL 99mTc–HMPAO shortly after PCI, via a Dispatch Catheter™, followed by a whole body scan to evaluate the distribution of the 99mTc–HMPAO, as well as a thallium–201 (TI–201) myocardial scan to evaluate myocardial perfusion. The major adverse cardiac events (MACE) were assessed during a one–year clinical follow–up. Results On histopathological analysis, the neointimal areas were 1.2±0.6 and 2.7±0.4 mm2 (p=0.002), and the histopathological areas of stenosis were 27.16.3 and 53.4±5.2% in Groups I and II (p=0.001), respectively. In the clinical study, there was no in–hospital MACE. On a quantitative coronary angiographic analysis, the minimal luminal diameter was increased from 0.4±0.3 to 2.9±0.2 mm, and diameter stenosis decreased from 84.2±9.5 to 16.3±11.0% following PCI. Follow-up CAG was performed in 9 cases (81.8%) and restenosis occurred in 2 (22.2%). On a follow-up CAG, the minimal luminal diameter, diameter stenosis rate, lumen loss and loss index were 2.0±0.8 mm, 27.7±2.9%, 0.7±0.7 mm and 0.2±0.3, respectively. During the one–year clinical follow–up there were no cases of death or acute MI, but two cases of target vessel revascularization (18.2%). Conclusion Local delivery of 99mTc–HMPAO, a novel radiotherapy, can be used safely and effectively for coronary stent restenosis.