Inhibition of neointimal hyperplasia caused by balloon injury of porcine coronary artery by an endovascular Ho-166 application

Neointimal hyperplasia following ballon angioplasty procedure for an occlusive coronary artery (CA) disease is one of the important contributing factors of restenosis. The purpose of our study was to investigate the effectiveness of intravascular Ho-166 (T1/2 : 1.15d, Eβ : 1.84MeV, R : 8 mm) application in inhibition of neointimal formation after the ballon injury to porcine coronary arteries. Nineteen domestic pigs weighing 25∼35 kg underwent balloon injury (balloon/artery ratio : 1.3 ∼ 1.4) to the proximal portions of LAD and LCX. One injured site was randomly irradiated by keeping liquid form of Ho-166 within the balloon for sufficient time to deliver beta radiation (0, 9, 18 Gy to 1mm depth). Four weeks later, pigs were sacrified and hearts were perfusion-fixed. Serial 2 to 3 μm slices of CAs were processed and embeded in paraffin. The maximal initimal thickness (MIT), luminal area, intimal area and vessel areas were measured. MIT was 0.48±0.13 mm in control ( 0 Gy, 32 sites) 0.42 ±0.05 in 9 Gy (20 sites) and 0.14 ±0.08 in 18 Gy (23 sites) group (P<0.05 vs control). Intimal area and smooth muscle proliferation was significantly reduced in 18 Gy group. Intra-balloon delivery of liquid form Ho-166 is feasible and effective in inhibiting neointimal hyperplasia caused by PTCA in swine model. This method may be able to reduce tha rate of restenosis following balloon angioplasty