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.