The mechanism of transluminal angioplasty: evidence for formation of aneurysms in experimental atherosclerosis.

Quantitative histologic examination (morphometric analysis) of pressure-perfused rabbit atherosclerotic arteries was used to determine whether compression of atheromatous material occurs with transluminal angioplasty. Experimental atherosclerosis was developed in both iliac arteries, with transluminal angioplasty performed on the left iliac while the right iliac served as a nondilated control. Angiography showed equal degrees of luminal narrowing before angioplasty (p = NS). Angioplasty reduced the left iliac narrowing in all animals studied. Morphometric analysis of histologic sections of the left and right iliac arteries disclosed significant differences in luminal and total vessel areas (p less than .05), whereas arterial wall (intima and media) areas were similar (p = NS). Dilated areas often demonstrated marked intimal splitting with dissection into the media. At higher magnification, loss of nuclear staining and dense layers of extracellular matrix consistent with stretching were frequently seen. It is concluded that the major mechanism of successful transluminal angioplasty is stretching of the vessel, resulting in localized aneurysm formation. Intimal splitting implies inelasticity of the neointima. No evidence of compression and remodeling of atheromatous material was disclosed in this study.