Microwave thermal balloon angioplasty in the atherosclerotic rabbit.

We evaluated the angiographic and histologic response of the coronary vessels of the atherosclerotic rabbit to microwave thermal balloon angioplasty. Sixteen rabbits with atherosclerosis of the external iliac arteries following a high fat diet and endothelial denudation were treated with either CBA or MBA. Four weeks following angioplasty angiography was repeated, and following the death of the animals, the vessels treated were excised for histologic evaluation. In vessels with MBA with peak temperatures of 85 degrees C there was an increase in luminal diameter immediately postangioplasty, from 1.66 +/- 0.32 mm to 2.54 +/- 0.23 mm (p < 0.05). The diameter at 4 weeks (2.29 +/- 0.74 mm) remained increased compared with the preangioplasty diameter (p < 0.05). With microwave angioplasty at 70 degrees C there was an increase in luminal diameter, from 1.92 +/- 0.37 mm to 2.40 +/- 0.22 mm (p < 0.05) immediately postangioplasty. This increase in diameter was not sustained at 4 weeks (1.86 +/- 0.28 mm). In the vessels treated with CBA there was no significant increase in diameter noted either immediately postangioplasty or at 4 weeks postangioplasty. In the thermally treated vessels, histologic evaluation revealed a loss of lipid-laden cells; it also revealed the formation of a concentric hypocellular fibrotic layer. Microwave thermal balloon angioplasty at 85 degrees C results in enhancement of the immediate and delayed response to angioplasty. Modification of the proliferative response to angioplasty may be accomplished with this modality.