An investigation into the role of iliac artery distensibility in balloon angioplasty

Abstract

Angioplasty is a common and successful technique for reopening stenosed arteries to blood flow. In spite of this achievement, a large number of patients restenose the site of angioplasty within only 6 months of the procedure. Clearly, the patient's response to angioplasty is not consistent but instead, appears to be unpredictable. Although angioplasty is often chosen over surgery, the mechanism by which angioplasty achieves luminal enlargement is not completely understood. The authors believe that the most important parameters that determines the response of a stenosed artery are the elastic properties of the artery and the composition of the plaque. Here, the authors examined the response of 4 isolated human common iliac arteries to balloon angioplasty. Aorto-iliac branches were harvested at autopsy from patients aged between 39 and 60 years. The specimens were cleaned of adipose tissue and were made pressure tight by tying-off side branches. The bifurcations were mounted in a high-resolution laboratory computed tomographic (CT) scanner and were studied at luminal pressures ranging from 8 to 24 kPa. Humidified air was used to pressurize the lumen because it kept the arteries moist during the experiment. Common iliac artery distensibility was measured from 2-dimensional (2D) cross-sectional slices obtained at seven pressures both pre- and post-angioplasty. The diameter of the balloon was chosen to be 1.2/spl times/the diameter of the normal common iliac diameter. Following the acquisition of the 2D images, a 3-dimensional volume image was obtained at a luminal pressure of 13.3 kPa. The authors found a considerable change in the mechanical properties of the iliac arteries they have studied. Luminal cross-sectional area increased linearly with arterial pressure prior to angioplasty but became nonlinear following angioplasty. The variation in area with pressure was shown to have 2 components: an initial linear increase at low pressure followed by a plateau at higher pressures. Distensibility was calculated from the slopes of the luminal perimeter versus pressure graphs and were found to be linear pre-angioplasty, but nonlinear post-angioplasty. The authors speculate that angioplasty increases luminal area by tearing elastin sheets but this remains to be proven.