犬隻血管壁機械特性之超音波探討

Abstract

心血管疾病為臨床上的重要疾病，以超音波儀檢測血管壁機械特性的變化，可協助心血管疾病的早期診斷。超音波量測的血管壁機械特性包括內膜中層厚度、血管壁硬度及能量消散比率等。本研究利用超音波檢驗血管壁的機械特性，以台大應力所生醫研究室發展的vascular index(VI)軟體進行分析，並進一步探討血管壁機械特性發生變化的原因。實驗犬於麻醉穩定狀況下，以超音波量測膊動脈、橈動脈、股動脈、脛動脈與總頸動脈等血管，其包括(1)檢測老犬、成犬和年輕犬不同年齡的血管壁機械特性變化，(2)藥物導致血壓上升時血管壁機械特性的變化，(3)以氣球導管造成前肢膊動脈內膜傷害，定期檢測血管壁機械特性的連續變化，並於實驗結束時取下血管壁進行組織病理學探討，以與超音波量測的結果進行比對。實驗結果發現: 血管內膜中層厚度和管壁硬度會隨年齡而增加，能量消散比率則會減少；血壓上升時，可見到血管內膜中層厚度、管壁硬度及能量消散比率都會增加；以血管造形術誘導血管壁傷害後，在超音波檢查可見內膜中層厚度持續增加，血管壁硬度及能量消散比率在第1~4週會明顯上升，第8~12週時會逐漸下降，到第20週左右會再次上升。受傷血管壁組織病理學檢查可見受損血管內膜和中膜的增厚病變，Trichrome染色下可見到膠原纖維的增生，Picro-sirius polarization檢查在管壁增厚的病變中可見到粗與細膠原纖維的雙折光性，α-smooth muscle actin免疫化學染色證明平滑肌細胞增生移行至內膜。以上研究驗證動脈管壁受傷後的內膜中層厚度增加、硬度增加及能量消散比率的改變，與血管壁膠原纖維增加和平滑肌細胞的增生移行有關。

Cardiovascular disease is very important in clinic, and the detection of the change of mechanical properties of vessel wall is helpful for early diagnosis of cardiovascular disease. The ultrasonic examination of mechanical properties of vessel wall include intima-media thickness (IMT), stiffness, and energy dissipation ratio (EDR). In this study, the mechanical properties of arterial wall were examined with ultrasonography, and images data were analyzed by vascular index (VI) software which was developed by Biomedical Ultrasound Laboratory in the Institute of Applied Mechanics. After the dogs were anesthetized, the brachial artery, radial artery, femoral artery, tibial artery, and common carotid artery were examined by ultrasonography. The experiments included: (1) comparison of the arterial mechanical property among the dogs with different ages; (2) detection of the change of arterial mechanical property when blood pressure increased; (3) examination of the change of mechanical property on a regular time schedule after the brachial arteries were damaged by angioplasty. All damaged vessels were collected for histo-pathological study and compared with the result from ultrasonographic study. The values of IMT and arterial stiffness increased when animal getting old. The values of EDR decreased following with the increase of age. The IMT, arterial stiffness, and EDR increased when blood pressure elevated. Following the damage of brachial artery, the value of IMT increased continuously. The value of arterial stiffness and EDR increased at 1st~4th weeks, and then decreased at 8th~12th weeks. However the value of arterial stiffness and EDR increased again at 20th week. From the histo-pathological study, the thickening of intima and media of the damaged vessels could be observed. The increase of the collagen fibers could be observed with Trichrome stain. The birefringence of thick and thin collagen fibers could be observed simultaneously in the intimal lesion with Picro-sirius polarization. The proliferation and migration of smooth muscle cell in the intima was identified with α-smooth muscle actin immunochemical stain. The results of the study indicate that the changes of IMT, stiffness and EDR of the vessel wall are related with the increase of collagen fiber and the proliferation and migration of smooth muscle cell.