| Objectives: The 64-slice Spiral Computed Tomography is a non-invasive and a new method for early diagnosing and detecting coronary atherosclerotic heart disease, and can offer significant reference for clinic. Although 64-slice CT has high temporal resolution and spatial resolution, the image quality still be suffered tachycardia or arrhythmia. Because image quality concerned with heart rate and heart rhythm. The literature has reported image quality of 64-slice SCT was poor when the heart rate≥70 bpm.Therefore, the 64-slice SCT mainly confined to the peoples with regular heart rhythm and heart rate <70 bpm to evaluating the diagnostic accuracy for detecting coronary artery stenosis in cinical studies. The rarely studies were reported for the evaluation of patients with high heart rate (≥70 bpm) and arrhythmia .This part of population often excluded from the 64-slice SCT examining or using drugs to control heart rate below 70 bpm in rank. In our study, CAG is used to evaluate the diagnostic accuracy of 64-slice CT for detecting coronary artery stenosis, and used to estimate the image quality and diagnostic value in PCI and CABG or myocardial bridge-mural coronary artery etal in patients with tachycardia (heart rate≥70 bpm) or arrhythmia(including bearing premature and atrial fibrillation).Our object is to expand the indications of 64-slice SCT.Methods:1 Study subjects: During January 2009 to December 2010, we collected the data of 104 patients with heart rate <100 bpm to accomplishing 64-slice SCT and CAG in Beijing MeiTan General Hospital. The first 64-slice SCT examination is completed, and then the CAG be completed, tow methods for the 1-30 days interval. All patients have not history of iodine allergy.2 Imaging Method 2.1 64-slice SCT Examination Methods: using the U.S. Company GE Lightspeed 64 VCT machine to complete coronary artery scan. Scan range from the level of tracheal carina to the diaphragmatic surface of the heart the following 2 cm (Scan for patients after CABG ranges from the upper edge of the aortic arch to the diaphragmatic surface of the heart). Scan parameters: Thickness 0.20-0.22mm,Variable pitch 0.18-0.24:1,Tube voltage 120 kv,Tube current 670-700 mA, Tube rotation time 0.35 seconds /week, Contrast agent iopromide(Iopromide,370 mg I/mL) 1ml/kg weight, injection rate of 5.0-5.5ml/s, in contrast to the same injection rate to continue after an additional injection of 30 ~ 40 ml saline. Scan time 9-11 seconds. After all the scan is completed, the images is transmitted to phase post-processing workstation AW4.3, we will choose the best time phase to rebuilding the image reconstruction of MPR, CPR, MIP, VR and other post-processing with the reconstruction interval of 5% from 0% to 99% of the phase image in reconstruction of the original data menu, showing the main branches of coronary arteries.2.2 CAG Inspection methods: All of the patients underwent invasive CAG (COROSKOP/HICOR). Usually, the right radial artery is punctured by local anesthesia, using 5F MP multi-function angiography catheter or 5F JL and JR angiography catheter to complete the left and right coronary artery angiography. Contrast agent iopromide(Iopromide,370 mg I/mL), injection rate of 4-8ml/s. Left coronary artery angiography used 4 to 6 individual bits of the projection, right coronary artery angiography by 2 to 3 individual bits of the projection.2.3 Evaluation of coronary artery: All of the coronary arteries and it,s branches no less than 2mm,were assessed. The degree of coronary artery stenosis were measured to used the international common methods, vascular stenosis=( Narrow proximal end of the normal vessel diameter- Diameter stenosis) / Narrow proximal end of the normal vessel diameter×100%. According to the suggestion of American Heart Association, the coronary arteries were divided to 13 segments. Image quality is divided into 5 grades. stenosis(50%～74%)and severe stenosis(≥75%).2.4 Evaluation of results and statistical analysis: Results by Beijing MeiTan General Hospital Department of Radiology and Heart experienced Physicians were assessed. The sensitivity, accuracy, specificity, positive and negative predictive value of detecting coronary stenosis by 64-slice SCT were compared with CAG in study group (tachycardia or arrhythmia patients) and control group (Sinus rhythm and heart rate <70 bpm). 64-slice SCT and CAG has detected the degree of coronary artery stenosis to be expressed as a percentage, theχ~2 test was used to compare the detection of rate, a value of p <0.05 indicated a statistically significant difference; The Pearson's correlation coefficient is used to compare correlation data between the degree of stenosis evaluated by 64-slice SCT and CAG in study group and control group.Results:1 A total of 104 patients was selected(age range is from 44 to 80 year old, mean age 66.39±8 years), among them,64 patients with tachycardia(heart rate≥70/bpm, heart rate fluctuations in the 70 ~ 93 bpm)and arrhythmia are a study group, including 10 cases of atrial fibrillation, atrial premature beats in 9 cases,12 cases of premature ventricular contractions, sinus arrhythmia in 2 cases, sinus rhythm and heart rate≥70bpm 31 cases;40 patients with Sinus rhythm and heart rate<70 bpm are a control group.2 A total of 821 segment were scanned in 64 patients (including 3 cases of abnormal development of coronary arteries), 2 cases of the total, image quality was considered moderate in 30.77%(8/26); The remaining 709 segments of 795 segments were able to achieve the level of≤3 scores, all of the image quality was considered moderate in 87.33%(717/821),image quality was considered good in 35.32%(290/821).A total of 512 segment were scanned in control group (including 2 cases of abnormal development of coronary arteries), of these 512 segments, image quality was considered moderate in 100 %( 512/512); Image quality was considered good in 90.43% (463/512). The image quality of study group were able to achieve the appraisable level, but lower than the control group(P<0.05).3 The CAG as the reference standard,64-slice SCT had a sensitivity of 54.17% and 87.50%(P<0.05),accuracy of 93.48% and 98.45%(P>0.05), Specificity of 97.15% and 99.37%(P>0.05), positive predictive value of 63.93% and 92.11%(P<0.05), and negative predictive value of 95.78% and 98.95%(P>0.05) for detecting less than 50% stenosis;It had a sensitivity of 52.38% and 91.18%(P < 0.05), accuracy of 95.88% and 99.22%(P >0.05),Specificity of 99.48% and 99.79%(P>0.05), positive predictivevalue of 89.19% and 96.88(P>0.05), and negative predictive value of 96.19% and 99.38(P>0.05)for detecting 50% to 74% stenosis;While it had also a sensitivity of 61.90% and 90.38%(P < 0.05),accuracy of 93.81% and 98.83%(P > 0.05),Specificity of 99.57% and 99.78%(P > 0.05),positive predictive value of 96.30% and 97.92%(P>0.05),and negative predictive value of 93.54% and 98.92%(P>0.05)for detecting more than or equal 75% stenosis in study group and control group.Theχ~2 test was used to analyzed the detection rate for evaluating coronary artery stenosis by 64-slice SCT, showing no statistically significant difference in all groups as compared with CAG, Chi-square value showing:χ~2=0.623 in slight stenosis,χ~2=0.745 in middle stenosis,χ~2=0.786 in severe stenosis,Overallχ~2=0.875, P>0.05; Two methods in the detection of coronary artery stenosis carry out quantitative analysis to showing a significant correlation(r = 0.736, P <0.01).4 64-slice SCT coronary artery imaging has clearly showed the position, shape, restenosis of stents and the condition, proximal and distal anastomoticstoma of grafts arteries, and to determined atherosclerotic plaque morphology and composition; and while it also has clearly discovered and diagnosed Myocardial bridge, the detection rate of myocardial bridge 26.56% (17/64), sensitivity was 85.71%.Conclusions:1 Adopted appropriate measures to scanning and after processing, image quality is no significant different for scanning coronary artery segments by 64-slice SCT in patients with selected tachycardia(≥70 bpm) or arrhythmia as compared with sinus rhythm and heart rate less than 70 bpm,but nearly 90% of the images have contented the level of clinical diagnostic request; Although 64-slice SCT has the low sensitivity, it has high accuracy and specificity for detecting the different degree of coronary artery stenosis as compared with CAG.2 64-slice SCT has done satisfactory evaluation for the shape and restenosis of coronary artery stents and grafts arteries in patients with tachycardia or arrhythmia; while it also can determine the nature of atherosclerotic plaque and identify MB-MCA. As a very good method, it also is used to screen the patients with CHD and recheck the patients who underwent coronary artery surgery such as incoronary stent implantation and coronary bypass surgery.3 The examinational indication of 64-slice SCT can be extended to most of tachycardia (heart rate 70 ~ 100 bpm) or arrhythmia of the population. |
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