The Value Of 64-slice Spiral CT In The Diagnosis Of Coronary Unstable Plaque

Background and Objective: The stable atherosclerosis constitute the pathophysiological basis of stable coronary artery disease, and the unstable atherosclerotic plaque (or vulnerable plaque,VP) is the major culprit of the pathophysiological basis of coronary artery disease. Abundant evidence suggests that severity of coronary artery disease is not mainly decided by the size, but by the stability of the plaque. Stability of the plaque is the major determining factor of occurrence and impact of ACS .Therefore, early recognition of unstable plaques and to take steps to ensure their stability is the goal of many reachers, and is the focus of intense researc in recent years. There are many types of investigation to detect plaques and their stability, most commonly the traditional means such as : coronary angiography(CAG); intravascular ultrasound(IVUS); coronary vascular microscopy(coronaryangioscopy CAS); flexible plane intravascular ultrasound (IVUS elastography); Temperature Measurement of coronary guide wire and so on. Except MRI technique, all above investigation are invasive procedures. A certain mortality rate of 0.15% and complications 1.5% also add to the high cost of investigation. Although MRI being on nuclear radiation, it has a lower spatial resolution and poor image quality. Various detection methods have their own advantages and disadvantages. The recognition performance for the characteristics of vulnerable plaque is varying. Since the earli 20th century, and the late 90s, more and more evidence shows that the inflammatory process in atherosclerosis occurred in the course of atherosclerotic plaque stability and plays an important role. High sensitivity CRP (hsCRP) is a reliable marker of reflecting coronary artery inflammation, high sensitivity, and precision, became a reliable means of detection of unstable plaque. But inflammatory markers for unstable plaque are only qualitative analysis, not quantitative visual evaluation. With the advent of multislice CT (MSCT) and ECG-gated Technology has made it possible to make MSCT be used in coronary angiography. Discovering a new method it showed good result of detecting of CHD. Mao Ding Biao and others analysing the experimental results, showed that MSCT can be recommended for non-invasive evaluation of coronary plaque morphology and composition. We hope to show MSCT, in diagnosis of unstable plaque can become safe, and a reliable method. HsCRP concentrations in this study can be a tool to determine the stability of plaque in selected patients with unstable angina, Evaluate, selective coronary angiography results to analysis the accuracy of 64-slice CT for the quantitative detection of unstable plaque and distribution, To investigate the reliability of 64-slice CT in the diagnosis of coronary plaque instability and clinical significance.Methods: 36 cases of unstable angina patients clinically diagnosed were enrolled, admitted in the hospital from March 2006 to September2006, of which 22 were male and 14 were female. Age range were from 37 to76 years (57.72±8.88).According to Braunwald grading, 15 cases were in grade I, 14 in grade II, and 7 in grade III . Firstly 64-slice CT coronary angiography, scanned the three main branches of the coronary artery (RCA,LAD,LCX). In accordance with coronary artery stenosis diameter ratio, the groups were divided into: "25% of normal, 25% -50% for mild, 51%～75% moderate, and high rates of more than 76%. Coronary plaque grouped into four categories: Lipid-rich plaque (also known as the soft patch), fibrous plaques, Calcified plaque, and mixed plaque (lipid and calcification coexistence). Then selective coronary angiography and multiple position angles coronary angiography were performed by two experienced physicians and analyzed the results of angiography, and compared the accuracy of 64MSCT for unstable plaque volume, location and the degree. All selected patients admitted in the hospital, had their fasting blood collected from the elbow about 4ml, the next morning for quantitative determination of hsCRP that can be used to compare 64MSCT for the stability of the plaque of the selected patients. Application of statistical methods were analyzed using SPSS 10.0 software, and testing standards a=0.05.Results: HsCRP between 3mg/l～7mg/l(4.5±1.11mg/l), all greater than 3mg/l. 108 main coronary of the 36 patients were scaned by 64-slice CT and CAG,(1) CAG found 73-vessel lesions with a detection rate of 67.6% while 64MSCT detected 67 lesions with a detection rate of 62%. Detection rate was of no significant difference (P> 0.05). Compared with CAG, the 64MSCT positive predictive value was 80%, and negative predictive value 97%, sensitivity 89%, specificity 94%, 6% false positive and false negative 11%, accuracy 91%.(2)For coronary angiography as the standard, MSCT detection rate of 79% of the total plaque; all branches of the Proximal and middle plaque detection rates were RCA77%,71%; LAD96%,77%; LCX89%,100%; Distal branches had far lower rate of≤50% detection ; RCA had a lower percentage detection rate of plaque then LAD and LCX. (3)In the 76 plaques detected by 64MSCT, 21.1% were accounted for soft plaque; calcified plaque 26.3%; and mixed plaque, non-fiber plaque 52.6%. Mild stenosis with soft plaque lesions was accounted in 50%, and only 13% of the lesions had severe stenosis; 65% of mixed plaque lesions had severe stenosis. Different types of plaque in the comparison between the degree of stenosis P<0.05, were statistically significant. After correctionα(α' =0.017), mild, moderate, to severe between february 2nd, mild-to-moderate P>0.017 no statistical significance was observed. Moderate-to-severe P<0.017 was statistically significant; mild-to-severe P<0.017 statistical significance. (4) 62.5% of soft plaque in patients with Braunwald classification grade, 18.8% were in Level III; 55% with mixed plaque in Level III patients and 15% in class.Different types of plaque in the overall between classification P<0.05, were statistically significant. After correctionα(α' =0.017) I , II, III between February 2nd, grade I -grade II and - grade III P>0.017, no significant difference between levels were observed; between Leve I - level III P<0.017 statistical significance. This shows that soft plaque constituent more in mild stenosis, and mixed plaque in severe stenosis. In Braunwald classification grade I the patients had more soft and calcified plaque;Grade II or III patients had more mixed plaque.Conclusion: (1) 64MSCT coronary angiography can be used in the quantitative diagnosis of coronary artery stenosis and plaque with a higher accuracy rate. Clear patch form, location and length of the relationship between the branches of coronary plaque also can be evaluated. (2) 64MSCT can made for non-invasive evaluation of coronary plaque morphology and composition; 64MSCT can by measurring CT value of different plaque composition to separate patches into soft plaque , fibrous plaques, calcified plaque, and mixed plaque. (3) soft plaque, calcified plaque, and mixed plaques with uncertainty, 64MSCT can described the composition of coronary atherosclerosisfor Qualitative evaluation of the stability of plaque and timely identification of vulnerable plaque for intervention treatment, and is of great significance for preventing the occurrence of ACS. (4) Compare to mild stenosis with soft plaque lesions, the more severe stenosis had mixed plaque lesions. in Braunwald classification grade I, for patients in the new grade or exacerbated by the serious angina, and soft plaque calcification prevalent was more ; pt with II, III grade resting recurrent angina had more mixed lesion.