Sixty-four Slice CT Coronary Angiography In The Assessment Of Myocardial Bridge

Part one:Effect of heart rate on the measurement accuracy of coronary artery with sixty-four slice CT: a study on pulsating cardiac phantomBackgrounds and Objective 64-slice CT coronary angiography has been widely put into use in clinic,and it is an important method to screen coronary heart disease.Howerver,its imaging quality was affected by many factors such as respiration,heart,beat,cardiac rhythm and reformation method,et al,among which the heart beat is the most important.At present,there are few reporters about the evaluation of measurement accuracy on coronary artery caliber.The purpose of this study is to explore the effect of heart rate on the accuracy of measurement and provide the basis for further study of myocardial bridge.Materials and Methods An adjustable pulsating cardiac phantom(GE) was used with cardiac pulsating rates at 0,40,45,50,55,60,65,70,75,80,85,90,95 and 100 beats per minute(bpm).The rotation speed was 0.35s.All raw data were reconstructed using two-sector reconstruction algorithm at 75%R-R interval.All date were analyzed by SPSS 10.0 statistical software package.Test of normality and one-way ANOVA were performed among groups.Difference with P＜0.05 was considered as significant.Results.Image quality decreases with the increase of heart rate.When the heart rate reached 80bpm,the imitated artery distorted and reconstructed defect appeared that leads to measurement disable.No regularity was found about the measured value of caliber with cardiac pulsating rate at 0,40,45,50,55,60,65,70,75,and 80 beats per minute(bpm). One-way ANOVA test demonstrated that there was no difference between real value and measured value when heart beat is less than 75bpm(P＞0.05),great difference exists between real value and measured value when heart beat more than 80bpm(P＜0.05).Conclusions The heart package for measuring diameter value in AW4.2,is an accurate tool to be used in the measurement of coronary artery when the heart beat is less than 75bpm.Part two:A quantitative assessment of the myocadial bridge with sixty-four slice CT coronary angiographyBackgrounds and Objective Myocardial bridge is always considered to be an inborn benign myocardial disease,but some researchers found that the myocardial bridge can cause myocardial ischemia,angina pectoris and et al.Coronary conventional angiography(CCA) is the golden standard in the dignosis of myocardial bridge.The incidence of myocardical bridge found by coronary conventional angiography(0.5%-2.5%) is significant lower than incidence by autospy(15%-85%).Sixty-four slice CT is characteristic of high temporal and spatial resolution,which may help detect and evaluate myocardial bridge exactly.The aim of the present study is to analyze the prvalence and the morphological features of myocardial bridge quantatively with 64-slice CTA.There remains contradiction about wether the long-term pression of myocardial bridge on mural coronary artery can cause atherosclerosis of the coronary artery adjecent to MBThe other purpose of this study is to explore the relationship between myocardial bridge and the adjcent coronary atherosclerosis.Materials and Methods The 64-slice CT images of 1247 patients with suspected or documented coronary artery disease were analyzed retrospectively by two experienced radiologists.When consistency was obtained by the independent interpretations,the diagnosis of MB and atherosclerosis could be confirmed.The length and thickness of MB were measured,and location of MB was recorded.The relationship between thickness of MB and diastolic narrowing of MCA was evaluated,a correlation between diastolic narrowing of isolated myocadical bridge and clinical symptom was made.The atherosclerotic plaque was divided by the location into the plaque of atherosclerosis in the coronary artery segment proximal to the bridge and the plaque of atherosclerosis in the coronary artery segment distal to the bridge according to MB.A comparison was made between the occurrence of AS in patients with and without MB.Results Among 1247 patients,383 MB were detected(30.7%,383/1247).Most of them located in left anterior descending artery(66.8%,256/383).The length of MB was 16.9 mm±9.4 mm and the thickness of MB was 3.5 mm±3.1 mm.There was significant correlation between the length and the thickness of MB(r=0.232,P＜0.05).The thickness of myocardial bridge in patients with moderate or severe stenosis was significant higher than that in patients with normal or mild stenosis(P=0.016).There was significant correlation between the diastolic narrowing of isolated myocadical bridge-MCA and clinical symptom(χ~2= 11.77, P＜0.05) There are 95 atherosclerosis plaques adjecent to MB in the 383 MB patients.The occurrence of AS in the proximal segment was higher than the distal segment and only one plaque was happened in MCA.There are 85 atherosclerotic plaques in LAD adjecent to MB (90.5%,86/95).Great difference was found between the presence of atheromatous changes in LAD with myocardial bridge and corresponding control group(P=0.017).There was positive correlation between diastolic narrowing of tunnelled artery and percentage of its atherosclerotic stenosis(r=0.842,P=0.002).Conclusions Sixty- four slice CT is a relatively exact method in the diagnosis of MB and can be used to evaluate the anatomical characteristics of MB quantatively.MB is commonly found in the middle segment of LAD.There was correlation between the length and the thickness of MB,between thickness of MB and diastolic narrowing of MCA.There was significant correlation between the diastolic narrowing of isolated myocadical bridge-MCA and clinical symptom The incidence of atherosclerosis in coronary artery proximal to MB is the highest.The existance of myocardial bridge is correlated with coronary atherosclerotic plaque formation.The development of atherosclerosis predisposes to happen in the coronary artery proximal to the bridge.Myocardial bridge should be considered as a risk factor in the evaluation of coronary artery disease.