Noninvasive coronary angiography with 16-detector row CT: effect of heart rate

PURPOSE: To evaluate the effect of heart rate on the quality of coronary angiograms obtained with 16-detector row computed tomography (CT) by using temporally enhanced three-dimensional (3D) approaches. MATERIALS AND METHODS: The local ethics committee approved the study, and informed consent was obtained from all patients. Fifty patients underwent coronary CT angiography (heart rate range, 45-103 beats per minute). Raw data from helical CT and electrocardiography (ECG) were saved in a combined data set. Retrospectively ECG-gated images were reconstructed at preselected phases (50% and 80%) of the cardiac cycle. A 3D voxel-based approach with cardiac phase weighting was used for reconstruction. Testing for correlation between heart rate, cardiac phase reconstruction window, and image quality was performed with Kruskal-Wallis analysis. Image quality (freedom from cardiac motion-related artifacts) was referenced against findings at conventional angiography in a secondary evaluation step. Regression analysis was performed to calculate heart rate thresholds for future beta-blocker application. RESULTS: A significant negative correlation was observed between heart rate and image quality (r = 0.80, P < .001). Motion artifact-free images were available for 44 (88%) patients and were achieved consistently at a heart rate of 80 or fewer beats per minute (n = 39). Best image quality was achieved at 75 or fewer beats per minute. Segmental analysis revealed that 97% of arterial segments (diameter > or = 1.5 mm according to conventional angiography) were assessable at 80 or fewer beats per minute. Premature ventricular contractions and rate-contained arrhythmia did not impede diagnostic assessment of the coronary arteries in 10 (83%) of the 12 patients affected. CONCLUSION: Motion-free coronary angiograms can be obtained consistently with 16-detector row CT scanners and adaptive multicyclic reconstruction algorithms in patients with heart rates of less than 80 beats per minute.     

心室率、心室率波动及心电编辑对心房颤动患者64层螺旋CT冠状动脉成像质量的影响

目的 探讨不同心室率、心室率波动对心房颤动患者64层螺旋CT冠状动脉成像(CTCA)图像质量的影响程度以及心电编辑对图像质量改善的有效性.方法 50例心房颤动患者行CTCA检查.评价心电编辑前后各节段冠状动脉血管的图像质量(优、中、差).用X~2检验分析不同心室率、心室率波动程度间及心电编辑前后图像质量的差异程度,用Pearson方法分析平均心室率及心室率波动程度与图像质量间的相关性.与冠状动脉造影结果进行比较,计算敏感性、特异性、阳性预测值、阴性预测值.结果 50例心房颤动患者,平均心室率47～153次/min,平均(89±23)次/min;心室率波动程度7.7～36.8次/min,平均(18.2±6.1)次/min.共评价冠状动脉血管节段704段,最终不可用于诊断的冠状动脉血管节段24段(3.4%),6例患者(12.0%)的CTCA图像中部分血管段无法满足诊断需要.平均心室率＞100次/min时图像质量差的冠状动脉节段数(11段)及心室率波动程度＞24次/min时图像质量差的冠状动脉节段数(11段)均明显增加(P＜0.05).冠状动脉各节段总体图像质量、右冠状动脉及远段冠状动脉血管图像质量与平均心室率及心室率波动程度均有显著相关性(r值分别为0.50、0.55、0.53、0.49、0.42和0.44,P值均＜0.05).心电编辑前后图像质量间差异有统计学意义(P=0.013).以患者为单位,与冠状动脉造影对照,诊断冠状动脉狭窄≥50%的敏感性、特异性、阴性预测值、阳性预测值分别为100%(6/6)、93.2%(41/44)、100%(41/41)、66.7%(6/9).结论 应用64层螺旋CT进行心房颤动患者的冠状动脉成像检查,可在一定平均心室率及心室率波动范围内通过心电编辑有效改善图像质量,提高检查成功率.     

Does two-segment image reconstruction at 64-section CT coronary angiography improve image quality and diagnostic accuracy?

PURPOSE: To prospectively evaluate the effect of single- versus two-segment image reconstruction on image quality and diagnostic accuracy at 64-section multidetector computed tomographic (CT) coronary angiography by using conventional coronary angiography as the reference standard. MATERIALS AND METHODS: The study design was approved by a human research committee; patients gave informed consent. The study was HIPAA compliant. Forty consecutive patients (22 men, 18 women; mean age, 61 years +/- 8 [standard deviation]) underwent both 64-section multidetector CT coronary angiography and conventional angiography. All data sets were reconstructed by using single- and two-segment image reconstruction algorithms, with resulting temporal resolution of 82.5-165 msec. Two experienced observers independently evaluated image quality and signs of coronary artery disease. A five-level grading scheme was used to grade stenosis (0%, <50%, <70%, <99%, 100%) and image quality (1[unacceptable] to 5[excellent]). Interobserver correlation, Spearman correlation coefficients, and diagnostic accuracy were calculated. RESULTS: Six hundred coronary artery segments were visible on conventional angiograms, of which 560 (93.3%) were seen by using single-segment and 561 (93.5%) were seen by using two-segment image reconstruction (P=.35). Mean quality scores were not significantly different (P=.22) for single- (3.1 +/- 0.9) and two-segment (3.2 +/- 0.8) reconstruction. Significantly (P=.03) better image quality was observed for two-segment reconstruction only at heart rates of 80-82 beats per minute, at which temporal resolution was approximately 83 msec. For grading coronary artery stenosis, correlation was 0.64 for single- and 0.66 for two-segment reconstruction (P=.43). Significant stenosis (>50%) was detected on a per-segment basis with 77.1% sensitivity and 98.6% specificity by using single-segment and with 79.2% sensitivity and 99.1% specificity by using two-segment image reconstruction. CONCLUSION: At heart rates of more than 65 beats per minute, use of two-segment reconstruction improves image quality at multidetector CT coronary angiography but does not significantly affect overall diagnostic accuracy compared with single-segment reconstruction.     

Analysis of heart rate and heart rate variation during cardiac CT examinations

RATIONALE AND OBJECTIVES: We sought to examine heart rate and heart rate variability during cardiac computed tomography (CT). MATERIALS AND METHODS: Ninety patients (59.0 +/- 13.5 years) underwent coronary CT angiography (CTA), with 52 patients also undergoing coronary artery calcium scanning (CAC). Forty-two patients with heart rate greater than 70 bpm were pretreated with oral beta-blockers (in five patients, use of beta-blocker was not known). Sixty-four patients were given sublingual nitroglycerin. Mean heart rate and percentage of beats outside a +/-5 bpm region about the mean were compared between baseline (free breathing), prescan hyperventilation, and scan acquisition (breath-hold). RESULTS: Mean scan acquisition time was 13.1 +/- 1.5 seconds for CAC scanning and 14.2 +/- 2.9 seconds for coronary CTA. Mean heart rate during scan acquisition was significantly lower than at baseline (CAC 58.2 +/- 8.5 bpm; CTA 59.2 +/- 8.8 bpm; baseline 62.8 +/- 8.9 bpm; P < .001). The percentage of beats outside a +/-5 bpm about the mean were not different between baseline and CTA scanning (3.5% versus 3.3%, P = .87). The injection of contrast had no significant effect on heart rate (58.2 bpm versus 59.2 bpm, P = .24) or percentage of beats outside a +/-5 bpm about the mean (3.0% versus 3.3%, P = .64). No significant difference was found between gender and age groups (P > .05). CONCLUSIONS: Breath-holding during cardiac CT scan acquisition significantly lowers the mean heart rate by approximately 4 bpm, but heart rate variability is the same or less compared with normal breathing.     

Coronary artery motion and cardiac phases: dependency on heart rate -- implications for CT image reconstruction

This study had institutional review board approval; written informed consent was obtained. The purpose was to prospectively determine the heart rate (HR) dependency of three-dimensional (3D) coronary artery motion by incorporating into analysis the durations of systole and diastole. Thirty patients (seven women, 23 men; mean age, 56.6 years +/- 12.7 [standard deviation]; HR: 45-100 beats per minute) underwent electrocardiographically gated 64-section computed tomographic (CT) coronary angiography to determine coronary motion velocities at bifurcation points. Significance of velocity differences (P < .05) was determined by using analysis of variance for repeated measures and Bonferroni post hoc tests. HR dependency was determined by using linear regression analysis. HR significantly affected 3D coronary motion (r = 0.47, P < .009) through nonproportional shortening of systole and diastole (r = -0.82, P < .001), leading to percentage reconstruction interval shifts of coronary velocity troughs and peaks (P < .01). Results suggest that image reconstruction algorithms at CT coronary angiography be adapted to the individual patient's HR.     

平均心率、心率波动和心率变异性对双源CT冠状动脉影像质量影响的研究

目的：评价平均心率、心率波动和心率变异性对双源CT冠状动脉影像质量的影响。方法：100例患者进行了双源CT冠状动脉血管成像。原始数据经多期相重建优选出最佳收缩期和舒张期影像,以4分法评定系统进行影像质量评价。利用Pearson相关分析评价平均心率、心率波动和心率变异性对冠状动脉的影像质量的影响,对有相关性者行进一步分析。结果：100例患者,共纳入分析的血管为299支,296支血管可满足影像评价（99％）。平均心率、心率波动和心率变异性对总的冠状动脉影像质量没有影响,仅平均心率对舒张期冠状动脉影像质量有负影响（P〉0．05）,尤其对右冠状动脉的影响更明显,70bpm以上时影像质量即下降,80bpm以上时影像质量甚至难以满足评价。结论：平均心率、心率波动和心率变异性对双源cr冠状动脉总的影像质量没有影响,但平均心率对舒张期冠状动脉的影像质量有负影响,对右冠状动脉的影响更大,当心率大于80bpm时,利用舒张期的数据难以获得RCA满意的影像质量,应该利用最佳收缩期的数据进行影像重组。     

320排CT冠状动脉成像平均心率对图像质量和辐射剂量的影响

目的:探讨不同心率条件下320排容积CT冠状动脉血管成像的图像质量和辐射剂量.方法:将259例临床怀疑或确诊的冠状动脉疾病的患者(含35例心律失常患者)分为3组;A组79例,心率≤65次/分;B组120例,65＜心率＜80次/分;C组60例,心率≥80次/分.扫描完成后选用最佳的重建时相,对冠状动脉进行容积再现(VR)...     

中等心率下64层螺旋CT 前瞻性心电门控冠状动脉成像的可行性研究

目的 采用回顾性心电门控模拟前瞻性心电门控冠状动脉CT 成像(CCTA),探讨前瞻性心电门控CCTA 在中等心率病人中的可行性.方法 本研究共纳入63 例病人[心率(HR)为65～75 次/min,心率变异性(HRv)＜5次/min,钙化积分＜400 分]行回顾性心电门控CCTA,扫描结束后以R-R 间期60%的相位为中心,按400 ms 占据曝光平均心率R-R 间期的比例以5%的间隔重建期相,以冠状动脉节段为单位,对所有重建的图像进行评分(5 分制:5分为优,1 分为差),以统计描述可用于诊断的冠状动脉节段数目所占比例评价前瞻性心电门控CCTA 在中等心率病人中的应用价值.结果 共有822 个冠状动脉节段参与评分,平均得分4.15±0.72,可用于诊断的冠状动脉节段数目比例为97.76%.结论 中等心率下前瞻性心电门控技术可通过预设60%采集期相,重叠时间设置为200 ms 可以重建出满足诊断的图像,且理论上可以大幅降低辐射剂量.     

基于动态容积 CT 前瞻性心电门控对快心率冠状动脉 CTA 的观察

目的：探讨心率>70次/min 的患者动态容积 CT 前瞻性心电门控技术的可行性。方法收集118例心率>70次/min患者的一般资料。所有患者行320容积扫描,前瞻性心电触发扫描模式,R 波后250~400 ms 多扇区采集,管电压100 kVp,自动管电流调节,对比剂采用碘克沙醇(370 mg I/mL)。记录所有患者的辐射剂量。将冠状动脉分为15个节段,由2名影像科医师测量冠状动脉 CT 值、图像评分。对结果进行统计学分析。结果各组间性别、年龄、体质量无显著性差异。心律整齐,心率>70次/min 者满足诊断率83.05%。心率>70次/min 组、心率>75次/min、心率>85次/min 组的图像主观评分分别为(4.23±0.72)分,(3.54±1.22)分,(1.87±0.74)分。各组间评分差异无统计学意义(F=5.125,P =0.0503)。辐射剂量随心率增加。结论动态容积 CT 采用前瞻性心电触发扫描模式,对心率>70次/min 患者行冠状动脉 CT 血管成像(CTA)检查可以得到满足临床诊断要求的图像质量。     

中等心率下64层螺旋CT前瞻性心电门控冠状动脉成像的可行性研究

目的采用回顾性心电门控模拟前瞻性心电门控冠状动脉CT成像（CCTA）,探讨前瞻性心电门控CCTA在中等心率病人中的可行性。方法本研究共纳入63例病人[心率（HR）为65～75次/min,心率变异性（HRv）〈5次/min,钙化积分〈400分]行回顾性心电门控CCTA,扫描结束后以R-R间期60%的相位为中心,按400ms占据曝光平均心率R-R间期的比例以5%的间隔重建期相,以冠状动脉节段为单位,对所有重建的图像进行评分（5分制：5分为优,1分为差）,以统计描述可用于诊断的冠状动脉节段数目所占比例评价前瞻性心电门控CCTA在中等心率病人中的应用价值。结果共有822个冠状动脉节段参与评分,平均得分4.15±0.72,可用于诊断的冠状动脉节段数目比例为97.76%。结论中等心率下前瞻性心电门控技术可通过预设60%采集期相,重叠时间设置为200ms可以重建出满足诊断的图像,且理论上可以大幅降低辐射剂量。     

ECG-gated reconstructed multi-detector row CT coronary angiography: effect of varying trigger delay on image quality

PURPOSE: To evaluate the effectiveness of electrocardiographically (ECG)-gated retrospective image reconstruction for multi-detector row computed tomographic (CT) coronary angiography in reducing cardiac motion artifacts and to evaluate the influence of heart rate on cardiac image quality. MATERIALS AND METHODS: Sixty-five patients with different heart rates underwent coronary CT angiography. Raw helical CT data and ECG tracings were combined to retrospectively reconstruct at the defined consecutive z position with a temporal resolution of 250 msec per section. The starting points of the reconstruction were chosen between 30% and 80% of the R-R intervals. The relationships between heart rate, trigger delay, and image quality were analyzed. RESULTS: Optimal image quality was achieved with a 50% trigger delay for the right coronary artery and 60% for the left circumflex coronary artery. Optimal image quality for the left anterior descending coronary artery was equally obtained at 50% and 60% triggering. A significant negative correlation was observed between heart rate and image quality (P <.05). The best image quality was achieved when the heart rate was less than 74.5 beats per minute. CONCLUSION: To achieve high image quality, the heart rate should be sufficiently slow. Selection of appropriate trigger delays and a decreasing heart rate are effective to reduce cardiac motion artifacts.     

64层螺旋CT心脏冠状动脉检查质量控制和扫描参数优化研究

目的 分析影响64层螺旋CT冠状动脉成像质量的各种因素，对扫描方法进行质量控制和优化。方法 对78例怀疑冠心病或冠心病复查患者进行64层螺旋CT冠状动脉检查，回顾性分析成像质量，探讨心率替代（override）功能的应用价值，分组分析扇区选择与心率对图像质量的影响以及心率与对比剂增强效果的相关性，优化扫描参数。结果 （1）心率替代功能的合理使用可以提高CT冠状动脉的成像质量；（2）心率70次／min以下的单扇区重组图像质量可以满足要求；70-79次／min之间的心率，选择双扇区重组图像的评分要高于单扇区；（3）预测对比剂总量70m1组的平均心率为60．7次／min，65．7％（23／35）的患者增强药量稍显不足；总量为60ml组的平均心率为71．1次／min，52．9％（18／34）的患者增强效果良好。结论 根据心率选择心率替代功能的使用，适当的扇区扫描模式和对比剂总量可以提高图像质量和冠状动脉检查的可靠性。     

320排CT冠状动脉成像心率(律)对图像质量和辐射剂量的影响

目的:探讨不同心率(律)的条件下,320排容积CT冠状动脉血管成像的图像质量和辐射剂量。方法:将259例临床怀疑或确诊冠状动脉疾病的患者分为两组:窦性心律组(S组)220例;心律失常组(N组)39例。其中S组分为:A组79例,心率<65bpm;B组102例,65≤心率<80bpm;C组39例,心率≥80bpm。扫描完成后选用最佳的时相,对冠状动脉进行容积重组(VR)、多平面重组(MPR)、曲面重组(CPR)。按照4分法将图像质量分类并统计分析,比较各组冠状动脉血管段的优良率、可评价性;记录各组的辐射剂量,比较辐射剂量的差异。结果:S组与N组之间冠状动脉血管段优良率和可评价性的差异均无统计学意义。所有病例共有9段冠状动脉不可评价。所有病例平均辐射剂量为(9.49±6.54)mSv;S组和N组平均辐射剂量分别为(8.45±5.7)mSv、(15.36±7.79)mSv,两组之间辐射剂量差异具有统计学意义(t=-5.29,P=0.000)。窦性心律各组辐射剂量差异具有统计学意义(2=126.43,P=0.000)。结论:320排CT能较好适应心率(律)变化,保证诊断图像质量,对于心率<65bpm以下的窦性心律患者辐射剂量降低显著。     

Multi-detector row CT coronary angiography: influence of reconstruction technique and heart rate on image quality

PURPOSE: To prospectively evaluate to what extent image quality in 16-detector row computed tomographic (CT) coronary angiography is a function of the heart rate and the image reconstruction technique used. MATERIALS AND METHODS: A total of 70 patients (49 men, 21 women; mean age, 59.1 years +/- 5.8 [standard deviation]) consecutively underwent multi-detector row CT coronary angiography; 49 patients additionally underwent coronary angiography. Image reconstruction was based on both relative and absolute timing. A total of 20 equidistant relative and absolute image reconstructed intervals were assessed by applying a four-step grading scale. Cluster and discrimination analysis, Spearman correlation analysis, and Wilcoxon and chi2 tests were used for statistical analysis. Institutional review board approval and written informed consent were obtained. RESULTS: Though significantly (P < .001) better image quality was observed for image reconstruction based on absolute timing and in patients with lower heart rates, influence on diagnostic accuracy was not significant. Irrespective of the reconstruction technique used, best image quality was observed in patients with a low heart rate for middiastolic reconstruction intervals (starting points: 61% of R-R interval [range, 40%-75%] and 599.3 msec after R [range, 450-840 msec]) and in patients with a high heart rate for end-systolic or early-diastolic intervals (starting points: 27.3% of R-R interval [range, 10%-45%] and 202.3 msec after R [range, 82-336 msec]). With regard to the vessel section and reconstruction technique, cutoff heart rates of the intervals were 64.0-68.5 beats per minute. Patients with stenoses of more than 50% were identified with 86% sensitivity and specificity, and there was no significant difference between relative and absolute timing (P = .99). CONCLUSION: In multi-detector row CT coronary angiography, image quality depends on the choice of a suited reconstruction interval. In patients with high heart rates, the best image quality can be obtained with end-systolic and early-diastolic intervals; in patients with low heart rates, the best results are achieved with middiastolic intervals.     

Safety, efficacy, and indications of beta-adrenergic receptor blockade to reduce heart rate prior to coronary CT angiography

For selected indications, coronary computed tomographic (CT) angiography is an established clinical technology for evaluation in patients suspected of having or known to have coronary artery disease. In coronary CT angiography, image quality is highly dependent on heart rate, with heart rate reduction to less than 60 beats per minute being important for both image quality and radiation dose reduction, especially when single-source CT scanners are used. β-Blockers are the first-line option for short-term reduction of heart rate prior to coronary CT angiography. In recent years, multiple β-blocker administration protocols with oral and/or intravenous application have been proposed. This review article provides an overview of the indications, efficacy, and safety of β-blockade protocols prior to coronary CT angiography with respect to different scanner techniques. Moreover, implications for radiation exposure and left ventricular function analysis are discussed.     

双源CT冠状动脉成像的图像质量及重组时相与心率的关系

目的 探讨双源CT冠状动脉成像的图像质量和重组时相与心率的关系.方法 对95例临床可疑冠心病患者进行双源CT增强扫描,检查前均不使用β受体阻滞剂控制心率.按扫描时心率分为3组:低心率组(≤70 次/min)26例,中心率组(71～90 次/min)37例,高心率组(t≥91 次/min)32例.利用回顾性心电门控重建出10%～100% R-R时相的图像,分析不同R-R时相冠状动脉的图像质量情况及其与心率的关系.结果 低、中、高心率3组图像质量评分分别为(1.08±0.27)、(1.32±0.58)、(1.47±0.61)分,低心率和中心率组图像质量评分差异无统计学意义(P＞0.05),低心率组图像质量评分显著优于高心率组(P＜0.05),中心率组和高心率组图像质量评分差异无统计学意义(P＞0.05).只有1.4%(19/1386)的冠状动脉节段不可评价.74例患者(77.9%)可在单一重组时相获得冠状动脉各段最佳图像质量.低心率组23例(88.5%)最佳重组时相在舒张中晚期;高心率组27例(84.4%)的最佳重组时相前移至舒张早期和收缩末期.结论 双源CT能够在相当宽的心率范围内提供优良的图像质量;多数患者可在单一时相获得各支冠状动脉最佳质量图像,随着心率的增快最佳重组时相从舒张中晚期前移至舒张早期和收缩末期.     

256层CT心电前置门控及回顾门控冠状动脉成像质量及辐射剂量比较

目的 比较256层CT前置门控冠状动脉CTA与回顾门控检查方法的成像质量及辐射剂量,探讨256层CT前置门控冠状动脉扫描方法的临床应用价值及局限性.方法 回顾分析177例冠状动脉256层CTA检查患者,其中前置门控86例,回顾门控91例.将冠状动脉主要分支分为9个节段评价,采用4分法评价图像质量,≥3分为可评价节段.采用t检验比较两种方法组可评价节段的百分比、患者的有效辐射剂量及图像噪声.结果 前置门控组86例中98.8%节段(765/774)为可评价节段.回顾门控组91例中99.6%节段(816/819)可评价.2组图像质量差异有统计学意义(t=2.51,P=0.01).心率<75次/min时,前置门控与回顾门控组的可评价节段分别为99.8%(647/648),99.7%(718/720),图像质量的差异无统计学意义(t=1.90,P>0.05).≥75次/min时,2组的可评价节段分别为93.6%(118/126)和99.0%(98/99).2组的可评价率差异有统计学意义(t=3.57,P<0.05).前置门控组及回顾门控组的有效辐射剂量分别为(4.4±0.5)和(10.3±1.5)mSv(t=33.4,P<0.00),前置门控扫描的剂量明显小于回顾门控扫描,下降幅度达60.0%.结论 256层CT前置门控冠状动脉扫描方法较回顾门控方法剂量显著降低,两种扫描方法得到的图像质量均较好.在低心率组图像质量两种方法相近,而高心率组前置门控较回顾门控法有差距.     

心率和心率变异对双源CT冠状动脉成像质量的影响

目的:评价心率和心率变异对双源CT(DSCT)冠状动脉成像质量的影响.方法:分析2007年7月～11月间163例临床怀疑或确诊冠心病患者的DSCT冠状动脉成像检查资料,探讨最佳时相重建时心率和心率变异对双源CT冠状动脉成像质量的影响.结果:163例患者增强扫描时平均心率为(69.3±14.6)次、min(42～124次/min),平均心率变异为(7.9±4.5)次/min(1～25 次/min),最佳时相重建时,LAD图像质最与心率间无相关性,RCA、LCX和总体图像质量与心率间存在相关性(P<0.05);各支冠状动脉图像质量和总体图像质量与心率变异间无相关性.结论:DSCT冠状动脉成像能在较人的心率和心率变异范围内完成对冠状动脉的观察,高心率对图像质量仍有一定影响,但足以满足诊断.     

Noninvasive coronary angiography using 64-slice spiral computed tomography in an unselected patient collective: effect of heart rate, heart rate variability and coronary calcifications on image quality and diagnostic accuracy

OBJECTIVE: The aim of this study was to assess the impact of heart rate, heart rate variability and calcification on image quality and diagnostic accuracy in an unselected patient collective. SUBJECTS AND METHODS: One hundred and two consecutive patients with known or suspected coronary artery disease underwent both 64-MSCT and invasive coronary angiography. Image quality (IQ) was assessed by independent observers using a 4-point scale from excellent (1) to non-diagnostic (4). Accuracy of MSCT regarding detection or exclusion of significant stenosis (>50%) was evaluated on a per segment basis in a modified AHA 13-segment model. Effects of heart rate, heart rate variability, calcification and body mass index (BMI) on IQ and accuracy were evaluated by multivariate regression. IQ and accuracy were further analysed in subgroups of significant predictor variables and simple regression performed to calculate thresholds for adequate IQ. RESULTS: Mean heart rate was 68.2+/-13.3 bpm, mean heart rate variability 11.5+/-16.0 beats per CT-examination (bpct) and median Agatston score 226.5. Average IQ score was 2+/-0.6 whilst diagnostic quality was obtained in 89% of segments. Overall sensitivity, specificity, PPV or NPV was 91.2%, 99.2%, 95.3% or 98.3%. According to multivariate regression, overall IQ was significantly related to heart rate and calcification (P=0.0038; P<0.0001). The effect of heart rate variability was limited to IQ of RCA segments (P=0.018); BMI was not related to IQ (P=0.52). Calcification was the only predictor variable with significant effect on the number of non-diagnostic segments (P<0.0001). In a multivariate regression, calcification was also the single factor with impact on diagnostic accuracy (P=0.0049). CONCLUSION: Whilst heart rate, heart rate variability and calcification all show an inverse correlation to IQ, severe calcium burden remains the single factor with translation of such effect into decrease of diagnostic accuracy.     

Efficacy of pre-scan beta-blockade and impact of heart rate on image quality in patients undergoing coronary multidetector computed tomography angiography

OBJECTIVE: While beta-blockers are routinely administered to patients prior to coronary computed tomography angiography (CTA), their effectiveness is unknown. We therefore assessed the efficacy of beta-blockade with regards to heart rate (HR) control and image quality in an unselected patient cohort. METHODS: We studied 150 consecutive patients (104 men/46 female; mean age, 56+/-13 years) referred for coronary CTA. Intravenous metoprolol (5-20mg) was administered to patients with a HR >65 beats per minute (bpm). The goal HR was defined as an average HR <65 bpm without a single measurement above 68 bpm. RESULTS: Overall, 45% (68/150) of patients met the HR criteria for beta-blocker administration of which 76% (52/68) received metoprolol (mean dose 12+/-10mg). Of the 52 patients who received beta-blocker versus the 98 who did not, 18 (35%) versus 62 (64%) patients achieved the goal HR, respectively. All patients who achieved the target HR had an evaluable CTA while five patients who did not achieve the target HR had at least one non-evaluable coronary artery due to motion artifact. There was also a significant reduction in any motion artifact among those who achieved the goal HR as compared to those who did not (p=0.001). Logistic regression revealed an increase in the odds of stair step artifact of 11.6% (95% CI: 2.4% decrease, 27.5% increase) per 1 bpm increase in the standard deviation of scan HR. CONCLUSION: Overall, efficacy of beta-blocker administration to reach target HR is limited. Improvements in CT scanner temporal resolution are mandatory to achieve consistently high image quality independent of HR and beta-blocker administration.