BACKGROUND: Magic TouchTM is a sirolimus based nano carrier balloon. We aimed at finding the excipient:drug ratio with the highest capacity to inhibit neointimal proliferation 28 days after the use of this balloon after bare metal stenting in porcine coronary arteries. METHODS: Fourteen domestic pigs with coronary bare metal stenting followed by dilation (60 seconds) using balloons with an excipient:sirolimus ratio of 1:1, 0.5:1, 0.25:1, 1:0 or a control balloon were evaluated. After 28 days neointimal hyperplasia was assessed by optical coherence tomography and histopathology. RESULTS: Percent neointimal hyperplasia (%) assessed by optical coherence tomography and histomorphometry was 32.2 and 35.1, 28.1 and 33.4, 17.3 and 20.9, 28.6 and 30.2, and 37.9 and 42.3 in the groups with 0.25:1, 0.5:1, 1:1, 1:0 excipient:sirolimus ratios and control balloon, respectively (P = 0.03 for excipient:sirolimus 1:1 versus control balloon). The neointimal interstrut thickness (mm) was 0.23, 0.30, 0.16, 0.24 and 0.30 in the groups with 0.25:1, 0.5:1, 1:1, 1:0 excipient:sirolimus ratios and control balloon, respectively (P < 0.01 for excipient:sirolimus 1:1 versus control balloon). The scores of inflammation, injury and fibrin deposition were low and there was no significant difference among groups. CONCLUSIONS: There was a stepwise increase in inhibitory efficacy of neointimal proliferation as the excipient concentration increased; the lowest efficacy was observed with the 0.25:1 excipient:sirolimus formulation and the most intensive inhibition was observed with the 1:1 excipient:sirolimus formulation. The 1:1 excipient:sirolimus formulation significantly reduced neointimal proliferation when compared to the control group, with low inflammation and injury scores.
Angioplasty, balloon, coronary; Coronary restenosis; Stents; Sirolimus; Animal experimentation
