Imaging of Vulnerable Plaques in Coronary Artery Disease by Multidetector Computed Tomography

Atherosclerosis

Atherosclerosis is a chronic and multifocal immunoinflammatory, fibroproliferative disease of medium-sized and large arteries driven by lipid. Atherosclerosis is rarely fatal unless thrombosis supervene, causing an acute coronary syndrome. Therefore, for event-free survival, the vital question is not why atherosclerosis develops but rather why atherosclerosis, after years after indolent growth, suddenly becomes complicated with luminal thrombosis. The great majority of coronary plaques will remain quiescent, at least from a clinical point of view. Acute coronary syndrome is primarily precipitated by a ruptured plaque. The precipitating factor or condition may be found outside rather than inside the plaque. The challenge is to find the plaque(s) destined for the next thrombus-mediated heart attack(s), treat, and thus avoid the heart attack(s). Identification of vulnerable plaques has become a key issue. The natural history of individual plaques (risk of thrombosis) is unknown and needs to be established. Multidetector computed tomography (MDCT) can provide angiography and imaging of the vessel wall (detection, quantification and characterization of plaques). The intention of this project is to evaluate the accuracy of coronary MDCT in identifying and differentiating the morphology of coronary atherosclerotic plaques.

Atherosclerosis without thrombosis is rarely fatal. It is the acute thrombotic complications which account for disability and death. Therefore, for event-free survival, the question is not why atherosclerosis develops but rather why atherosclerosis, after years after indolent growth, suddenly becomes complicated with luminal thrombosis. Post-mortem and clinical observations indicate that patients with acute coronary syndromes often have many ruptured and/or active plaques in their coronary arteries. The challenge is to find the plaque(s) destined for the next thrombus-mediated heart attack(s), treat, and thus avoid the heart attack(s). Identification of vulnerable plaques have become a key issue. The natural history of individual plaques (risk of thrombosis) is unknown and needs to be established. Multidetector computed tomography (MDCT) can provide angiography and imaging of the vessel wall. Hypothesis: It is by CT-scanning possible to 1a) identify and differentiate the morphology of coronary atherosclerotic plaques. 1b) identify vulnerable plaques. Materials and methods: 1. Development of an MDCT scan protocol for accurate assessment of coronary artery plaque composition by ex vivo examination of human coronary arteries from the Institute of Forensic Medicine, University of Aarhus. Scan protocols parameters and intravascular contrast material will be varied to optimize accurate assessment of coronary plaque composition. MDCT will be compared to histopathology. 2. A cross-sectional study with clinical application of the efficiency parameters defined in sub-study 1. Forty consecutive patients with non ST-elevation myocardial infarction/unstable angina, and 80 consecutive patients with stable angina will be recruited and investigated with MDCT followed by CAG with IVUS/virtual histology. 3. A prospective, longitudinal study. After a period of 12 months all patients from sub-study 2 will be re-investigated. 4. Before the cross-sectional study a small pilot-study will be performed. Ten patients with non ST-elevation myocardial infarction/unstable angina will undergo MDCT and CAG with IVUS/virtual histology. These patients will after one months undergo another MDCT. This is done to make sure that it is possible to perform the planned longitudinal study. Research plan: 1. Development of an MDCT scan protocol for accurate assessment of coronary artery plaque composition. 2. Clinical application of the MDCT scan protocol for in vivo differentiation of coronary artery plaque morphology. Morphologic findings will be categorized and compared with IVUS/virtual histology for confirmation. 3. Re-evaluation of plaque density and morphology one year after inclusion by a second in vivo contrast-enhanced MDCT-scanning to define which morphological plaque categories are at risk of progression.

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