Clinical Research Of Dual-source CT Coronary Angiography For Patients With Complex Arrhythmias

BACKGROUND AND AIM: CT coronary angiography(CTCA) has relatively become a reliable and noninvasive tool in the examination of coronary artery disease. However, the successful rate of CTCA examination is still disturbed by many factors. Among them, arrhythmia is the biggest factor leading to CTCA failure. For patients with arrhythmia, among the methods for CT coronary angiography(CTCA), the retrospective ECG-gated cardio helical scan(RCH mode) is currently used. After the completion of data collection, the use of special software(ECG-edit software) for ECG editing processing is able to enhance image quality and increase the examination successful rates. But not all patients with arrhythmia can therefore be obtained to achieve the required diagnostically image quality, there is still a considerable number of patients fail to check. The adaptive prospective ECG-triggered cardio sequence scanning(APCS mode) technology has been gradually applied in clinical in recent years. There were some literatures reports that this technology could improve the success rate of CTCA for patients with pure atrial fibrillation and simple premature contraction. But the APCS is not yet applicable to all patients with arrhythmia including mixed type and complex arrhythmia.Based on the above clinical difficulties, the purpose of the study for patients with arrhythmia, especially in complex arrhythmias, is to research CTCA technology, in order to improve the image quality and the examination success rate of CTCA for patients with complex arrhythmia.Part I: Correlation between the CTCA imaging quality and type of cardiac arrhythmia of patients under conventional RCH modeOBJECTIVE: For CTCA in patients with arrhythmia, the retrospective ECG-gated cardio helical scan(RCH mode) and ECG editing is currently used. Some patients with arrhythmia can therefore be obtained to achieve the required diagnostically image quality, but there is still a considerable number of patients fail to check. So are the following questions arising: how about image quality and overall successful ratefor arrhythmic patients with CTCAunder the mode of RCH? What are differences between the different types of arrhythmic patients in image quality and successful rate under RCH mode? What is the relationship between CTCA image quality and types of arrhythmia? Is there any regularity ? These clinical problems in previous literature have not been systemically reported. Therefore, at the first part of this paper, the study of CTCA image quality at conventional RCH model in patients with arrhythmia was firstly undergoing in order to answer the above questions, and try to screen out those types of arrhythmia(named complex arrhythmias) in whichthe CTCA image quality still did not meet the diagnostic requirements under RCH mode although ECG-edit was done.METHODS: A prospectively continuous 4385 cases underwent CTCA in our hospital, including 1102 cases with arrhythmia, in which, according to inclusion and exclusion criteria of patients in the experimental group, a total of 795 cases were enrolled in the study. Among them, 486 cases(486/795) underwent invasive coronary angiography(ICA) examination due to the need of illness 2 weekslater. Thenthose patients enrolled in the experimental group were divided into several subgroups according to different types of arrhythmia. Another 100 caseswith regular heart rhythm were randomly selected as a control group. All patients performed CTCA using conventional retrospective ECG-gated helical scan mode(RCH).The protocols were the following: scanning pitch 0.20-0.22, closing ECG-plusing, 30%-80% as the full dose scan RR interval, the tube voltage 100-120 k V, tube current 360-420 m A, using Caredose 4D, multi-phase reconstruction of ECG-edit after scanning, image processing at the dedicatedworkstation including coronary reconstruction and analysis.All patients’ CTCA image quality were evaluated, the chi-square testt test,andlinear correlation analysis were used to compare the relative differences in the study.Taken ICA as the gold standard,the assessment accuracy of CTCA for the evaluation of coronary artery stenosis was made in patientswith arrhythmia.Results: Among 795 cases of arrhythmia patients in the test group, 22 kinds of arrhythmic types occurred including sinus arrhythmia(59 cases), atrial arrhythmia(246), atrioventricular junctional arrhythmias(110), ventricular arrhythmias(222 cases), mixed type of arrhythmia(158 cases). ⑴In test group, the proportion of heart rate variability, the need of multi-phase reconstruction and ECG edit, and number of non-diagnosable segments increased significantly in comparison with the control group. As to these aspects, the difference between the two groups was statistically significant(t = 15.50, P = 0.000; χ 2 = 394.32, P = 0.000; χ2 = 248.28, P = 0.000; χ2 = 204.53, P = 0.000).While the proportion of diagnosable segments and patients decreased significantly in test group, and the difference between the two groups was statistically significant(χ 2=204.53, P=0.000; χ 2=26.63, P=0.000). ⑵In test group,there was no significant difference between the proportion of non-diagnosable patients with different heart rate variabilityintervals(χ2 = 0.14, P = 0.706), and so was the difference between the proportion of non-diagnosable patients with different ventricular rate intervals(χ2 = 0.35, P = 0.552).⑶In these aspects of diagnosable rates of segments, diagnosable rates of patients, and segment average scores of segments, there were statistically significant differences between the inter-groups of 22 types of arrhythmias(χ 2=1340.73, P=0.000; χ 2=194.75, P=0.000; F=34.62, P=0.000). Based on the twolevels of segments and patients,the diagnosable rates were less than 80% includingpaired atrial premature beats, paroxysmal atrial tachycardia, atrioventricular block, trigeminy of ventricular premature, paired PVCs, frequent mixed premature beats, paroxysmal atrial tachycardia with PVC, paired PVCs with atrial premature, paroxysmal atrial tachycardia with paired PVCs.All these were defined as complex arrhythmias. ⑷ In test group, patients were devided into diagnosable and non-diagnosable sub-groups. The proportion rates ofpalpitations, mixed arrhythmia, and complex arrhythmia were statistically significant between the two sub-groups(χ 2=35.66, P=0.000; χ 2=35.81, P=0.000; χ 2=105.71, P=0.000). ⑸Taken ICA as the gold standard, the sensitivity, specificity, positive predictive value and negative predictive value were 96.8%, 93.9 %, 81.2%, 99.1%, respectively diagnosed by CTCA(stenosis rate > 50%)in test group. ⑹ average effective radiation dose in test group(11.4 ± 4.7 m Sv) was higher than that in control group(4.1 ± 1.5 m Sv) with the statistically significant difference(t = 15.43, P = 0.000). Average time in test group(17.5 ± 6.6 min)was much higher than that in control group(5.7 ± 1.8 min) with significant differences(t = 17.79, P = 0.000).⑺In test group, patients were devided into two sub-groups of complex and non-complex arrhythmia. There were statistically significant differences in these aspects of atypical angina(χ 2 = 33.22, P = 0.000), palpitations(χ 2 = 65.57, P = 0.000), diagnosable segments(χ 2 = 816.47, P = 0.000), diagnosable patients(χ 2 = 109.96, P = 0.000), and time-consuming for post-processing(t = 12.94, P = 0.000) between the sub-groups.Conclusions: ⑴ The successful ratesof CTCA for patients with arrhythmia were less than those with regular rhythm. RCH combined ECG-edit, might significantly improve the image quality of CTCA in part of arrhythmia patients, but there were still some failed CTCA for some patients with arrhythmia ⑵Patients with different types of arrhythmias, successful ratesof CTCA were different under RCH + ECG-edit technology; the main factors affecting the successful rate was not the heart rate variability and average heart rate, but the type of arrhythmia. ⑶Patients with paired atrial premature beats, paroxysmal atrial tachycardia, atrioventricular block, trigeminy of ventricular premature, paired PVCs, frequent mixed premature beats, paroxysmal atrial tachycardia with PVC, paired PVCs with atrial premature, orparoxysmal atrial tachycardia with paired PVCs,successful rates of CTCA were still low, thus these types of arrhythmias were named complex arrhythmias in this studey.Part Ⅱ: Clinical study for CTCA imaging quality of arrhythmic patients under APCS technologyObjective:In view of the new generation of prospective ECG gating technique with a larger full dose scan tolerance,an identification of R-wave rhythm abnormalities,as well asa function of ignorance or compensation for abnormal R-wave in an interaction with the sequential scanning(i.e.function of advanced arrhythmic compensation),in this study adaptive prospective ECG-triggered cardio sequence scanning(APCS)technology for patients with arrhythmias was used for CTCA examination.For such policy change compared to conventional mode of RCH recommended in past and literature,the differences between the two modes were sequentially observed.Methods:A prospectively continuous 2056 cases underwent CTCA, including 463 cases with arrhythmia, in which, according to inclusion and exclusion criteria, a total of 360 cases with arrhythmia were enrolled in the study, including 180 cases of the test group(using APCS mode) and180 cases of the control group(using RCH mode). 159 casesfrom the 360 cases underwent ICA examinationin 2 weeks after examination of CTCA. Diagnosable rates of image and image quality scores were compared between the two groups using t test and chi-square test of randomized block design. The difference of image quality from the different phases of reconstruction was compared using chi-square test of R×C. Taken ICA as the gold standard, the assessment accuracy of coronary artery stenosis of CTCA was evaluated for arrhythmic patients. The difference of radiation dose between test and control groups was assessed using t test of randomized block.Results: ⑴The difference between the test and control groups for the constitution of various types of arrhythmia was not statistically significant(χ 2=8.33, P=0.983). As to the two levels of segments and patients, diagnosable segments(2409 / 2575,93.6%), diagnosable patients(161 / 180,89.4%), and coronary artery segmental scores(3.64 ± 0.71) in test group were higher than those of control group(2121/2538, 83.6%; 134/180, 74.7%; 2.79±0.85), with the statistically significant difference(χ 2=126.09, P=0.000; χ 2=13.65, P=0.000; t=10.26, P=0.000). ⑵ Image quality scores by the absolute value of the best systolic phase for CTCA reconstruction CTCA best were significantly better than the other three phases(absolute value of best diastolic, relative value of best systolic, and relative value of optimal diastolic phases) with a statistically significant difference after comparing one to another(χ 2=284.76, P=0.000; χ 2=310.41, P=0.000; χ 2=55.05, P=0.000) in test group. ⑶ In test group, the optimum image reconstruction phase for patients with the average heart rate >70 bpm was ranged 250-400 ms after R-wave, but for patients with the average heart rate <70 bpm, 300-650 ms range. ⑷ Compared to ICA, the sensitivity, specificity, positive predictive value and negative predictive value were 98.2%, 96.1%, 82.3% and 99.4%, respectively for test group in diagnosing coronary artery stenosis(> 50%). ⑸ The mean effective radiation dose in test group(6.8 ± 2.9m Sv) was much lower than that in control group(11.1 ± 4.8 m Sv) with a statistically significant difference between the two groups(t = 10.29, P = 0.000).Conclusions: ⑴ For patients with arrhythmia, the successful rate of CTCA using APCS mode was significantly higher than that using RCH mode. ⑵ The CTCA image quality by absolute value reconstructed phase was superior to that by relative value reconstructed phase in the process after ECG-editor for patients with arrhythmias. ⑶ For CTCA in patients with arrhythmia, the best absolute value of the reconstruction phase ranged 250-400 ms after R-wave to patients with high ventricular rate, but 300-650 ms to patients with low ventricular rate.Part Ⅲ: Clinical application research in CTCA imaging for arrhythmic patients under modified APCS technologyObjective: Because the deficiency of RCH mode might not be avoided which caused higher failure rate of CTCA for complex arrhythmic patients, and on the basis of the second part of research results, the full-dose exposure interval pre-set by absolute value and full-dose exposure of RR interval set by layered heart rate were used in this study, which was called as the modified APCS method. In this way, CTCA quality was analyzed in complex arrhythmic patients in order to further widen the indications of CTCA examination.METHODS: Patients were prospectively included in the continuity of a total of 2380 cases for CTCA examination, in which 135 patients were of complex arrhythmias. According to the inclusion and exclusion criteria in the study, 118 cases(118/135) were enrolled in. The selected patients were randomly divided into test group(group A, 40 cases) with modified APCS mode scanning, control group 1(group B, 39 cases) with conventional APCS scan mode, and control group 2(group C, 39 cases) with conventional RCH scan mode. Randomized block variance analysis was used to compare the index among the three groups including CT value, SNR, CNR, image quality score, radiation dose. The differences of diagnosable segments and patients in three groups were compared using chi-square test of R×C. The consistency of CTCA and ICA for diagnosis of coronary stenosis was analyzed using Pearson and Bland-Altman.Results: ⑴ For either the ascending aorta or coronary artery, the image quality parameters such as CT value, SNR and CNR of, showed no statistically significant differences among the three groups or between any two means(P> 0.05). ⑵ In view of coronary segment level, 518 diagnosable segments in group A(91.7%), 458 in group B(82.8%), 395 in group C(70.4%) were showed by CTCA. Among the three groups statistically significant difference was found(χ 2=19.19, P=0.000). In view of the patient level, 36 diagnosable patients in group A(90.0%), 32 cases in group B(82.1%), 21 cases in group C(53.8%) were showed by CTCA. There was statistically significant difference among the three groups(χ 2=15.17, P=0.000). ⑶ Taken coronary segments as a unit, ICA had a good correlation and consistency with CTCA(r = 0.810) for assessing coronary artery stenosis in group A. ⑷ Effective radiation dose in group A(4.1 ± 2.8m Sv) was minimum, showing a statistically significant difference compared to group B(6.5 ± 3.6m Sv) and group C(10.9 ± 5.2m Sv)(t = 3.31, P = 0.002; t = 7.26, P = 0.000).Conclusions: ⑴ As to patients with complex arrhythmias, the successful rate of CTCA under APCS technology was higher than that in RCH. Based on the modified APCS technique with the full-dose exposure interval pre-set by absolute value and full-dose exposure of RR interval set by layered heart rate, its image quality of CTCA was superior to that under the APCS mode commonly used in clinic with the full-dose exposure of RR interval set by relative value. ⑵ The modified APCS technology not only significantly increased the successful rate of CTCA in patients with complex arrhythmias, but also significantly reduced the effective dose a patient received.