Intravascular ultrasound and histology in in vitro assessment of iliac artery angioplasty

Intravascular Ultrasound Analysis of Correlation between Plaque-Morphology and Risk Factors in Peripheral Arterial Disease

OBJECTIVE

To analyze relationships between plaque-morphology classified by intravascular ultrasound (IVUS) and risk factors in patients with peripheral arterial disease (PAD).

METHODS

We performed IVUS in 203 patients with PAD. Multiple regression and logistic analysis were used to assess relationships between plaque-morphology (degree of calcification, presence of a lipid core, intimal flap and thrombus) and risk factors including diabetes mellitus, hypertension, dyslipidemia, estimated glomerular filtration rate (eGFR), HbA1c and the homeostasis model assessment-insulin resistance ratio (HOMA-IR).

RESULTS

IVUS data led to 22% of lesions being classified as soft, 18% as fibrous, 32% as calcified, and 28% as mixed. Calcification was present in the superficial and deep layers in 65% and 35% of cases, respectively, and a lipid core, intimal flap and thrombus were found in 31%, 5.4% and 3.0%, respectively. The calcified angle correlated with HbA1c and eGFR (p < 0.05). Associations were found between deep calcification and HOMA-IR (odds ratio: 4.4, p < 0.05) and a lipid core and hypercholesterolemia (odds ratio: 3.2, p < 0.05). The odds ratio for intimal flap was 15.6 times with hypercholesterolemia (p < 0.05) and 16.9 times with a high HOMA-IR (p < 0.01).

CONCLUSION

Plaque calcification and morphology are associated with chronic kidney disease, insulin resistance and dyslipidemia in PAD patients.

Quantification of dose perturbation by plaque in vascular brachytherapy

BACKGROUND

Dose prescription and reporting in vascular brachytherapy (VBT) is based on the assumption that the vessel wall is water equivalent, which does not consider a possible dose perturbation by plaque. As the extent of this perturbation is unknown, we aimed to quantify dose attenuation by atherosclerotic plaque for beta- and gamma-radiation.

MATERIAL AND METHODS

The dose delivered from Strontium-90/Yttrium-90 ((90)Sr/Y) and Iridium-192 ((192)Ir) sources with and without human peripheral arteries ((90)Sr/Y: n = 38, (192)Ir: n = 7) surrounding the respective delivery catheter was determined with radiochromic films. Plaque and vessel wall thickness were measured using light microscopy. From the ratio-attenuated doseunattenuated dose (dose perturbation factor: DPF) we determined averaged attenuation coefficients for atherosclerotic plaque (micro(P)) and the residual part of the vessel wall (micro(W)) by regression analysis based on the function DPF = exp(-micro(P) * plaque thickness -micro(W) * residual wall thickness).

RESULTS

Attenuation in case of (192)Ir was less than the measurement uncertainties. For beta-radiation correlation was found by discrimination between calcified and noncalcified plaque. Classifying noncalcified plaque as normal arterial tissue, the regression coefficient was r = 0.845 at micro(P)= 0.5356 mm(-1) and micro(W) = 0.0663 mm(-1).

CONCLUSIONS

Vascular brachytherapy with beta radiation in calcified arteries results in significant dose attenuation within the vessel wall, which can be calculated on knowing the vascular morphometry. Thus, plaque thickness should be taken into account in treatment planning and retrospective analyses.

Quantification of elastic recoil after balloon angioplasty in the iliac arteries

PURPOSE

Elastic recoil of the arterial wall has been shown to be responsible for a significant loss of luminal area after balloon angioplasty in the coronary arteries, but it has not been well studied in the peripheral arteries. Because elastic recoil depends on the presence of elastin in the arterial wall, and the amount of elastin varies by artery and proximity to the aorta, the importance of this response to angioplasty may be different in peripheral arteries. The purpose of this study is to document the degree of elastic recoil in the iliac arteries, and analyze variables that might influence the results.

MATERIALS AND METHODS

A series of 19 patients with 25 iliac artery stenoses underwent balloon angioplasty followed by placement of a Palmaz stent with the same-sized angioplasty balloon. The minimum luminal diameter of the lesion was measured before treatment, immediately after balloon angioplasty, and again after stent placement. The arterial diameter after stent placement was defined as the diameter of the inflated balloon. The degree of recoil was correlated with nine variables: patient age and sex, lesion location and length, lesion severity (as percent stenosis), the balloon:artery ratio, and three factors related to lesion morphology--complex versus simple, eccentric versus concentric, and calcified versus noncalcified.

RESULTS

Elastic recoil averaged 36% +/- 11% and ranged from 19% to 54% in this series of patients. The only variable that significantly influenced the degree of elastic recoil was the balloon:artery ratio (P =.039), which was directly related.

CONCLUSION

Elastic recoil is a significant limitation of balloon angioplasty in the iliac arteries. This study illustrates the importance of techniques that limit recoil, such as vascular stents, in angioplasty of the iliac arteries.