How does angioplasty work? Serial analysis of human iliac arteries using intravascular ultrasound.

BACKGROUND: Previous studies regarding the mechanism by which balloon angioplasty increases luminal patency have generally used animal models or postmortem specimens from occasional fatal cases of angioplasty performed in human patients. In either case, conclusions regarding participatory mechanisms have relied exclusively on nonserial, postangioplasty histopathological examination. METHODS AND RESULTS: In the present study, intravascular ultrasound examination was performed before and after balloon angioplasty in 40 consecutive patients with iliac artery stenoses. The areas of the arterial wall, plaque, lumen, and areas resulting from angioplasty-induced plaque fractures were measured immediately after angioplasty in vivo and compared with findings recorded immediately before angioplasty. Angioplasty increased luminal cross-sectional area (CSA) from 11.5 +/- 0.6 mm2 before angioplasty to 25.4 +/- 1.2 mm2 after angioplasty (p = 0.0001). CSA of the portion of the postangioplasty neolumen contained within angioplasty-induced plaque fractures measured 10.0 +/- 0.8 mm2; the neolumen excluding the area contributed by these plaque fractures measured 15.4 +/- 0.8 mm2. Thus, the area contained within plaque fractures accounted for 10.0 mm2 (71.9%) of the 13.9-mm2 increase in luminal CSA after angioplasty. Analysis of CSA occupied by atherosclerotic plaque disclosed that plaque CSA decreased from 33.8 +/- 1.8 mm2 before angioplasty to 22.5 +/- 1.5 mm2 after angioplasty (p = 0.0001). Plaque CSA was thus reduced ("compressed") by 11.3 +/- 1.1 mm2. Total artery CSA increased ("stretched") slightly from 45.3 +/- 2.6 mm2 before angioplasty to 47.8 +/- 2.0 mm2 after angioplasty (p = 0.0025). CONCLUSIONS: In vivo analysis of iliac stenoses by intravascular ultrasound immediately before and after angioplasty demonstrates that plaque fractures and "compression" of atherosclerotic plaque are the principal factors responsible for increased luminal patency resulting from balloon angioplasty. "Stretching" of the arterial wall provides an additional, but minor, contribution.