Noninvasive coronary angiography by contrast-enhanced electron beam computed tomography

Electron beam computed tomography (EBCT) is a cross-sectional imaging method with high temporal and spatial resolution. So far, it has mainly been applied for the detection of coronary artery calcifications which permit the very sensitive detection of coronary atherosclerosis even in the very early stages. However, after intravenous injection of a contrast agent, EBCT also permits the direct visualization of the coronary artery lumen. For these investigations, a volume data set is acquired that consists of 40 axial cross-sections of the heart (3 mm slice thickness). To evaluate the coronary arteries as to the presence of stenoses and occlusions, various forms of postprocessing, including shaded surface display, maximum intensity projection, and multiplanar reconstruction, are applied. The sensitivities and specificities for the detection of coronary artery stenoses and occlusions are about 90%. Best results are obtained for coronary artery bypass grafts, the left main coronary artery, and the left anterior descending coronary artery, while reduced image quality impairs the results for the right coronary artery and the left circumflex coronary artery.     

In vivo assessment of three dimensional coronary anatomy using electron beam computed tomography after intravenous contrast administration

Intravenous coronary angiography with electron beam computed tomography (EBCT) allows for the non-invasive visualisation of coronary arteries. With dedicated computer hardware and software, three dimensional renderings of the coronary arteries can be constructed, starting from the individual transaxial tomograms. This article describes image acquisition, postprocessing techniques, and the results of clinical studies. EBCT coronary angiography is a promising coronary artery imaging technique. Currently it is a reasonably robust technique for the visualisation and assessment of the left main and left anterior descending coronary artery. The right and circumflex coronary arteries can be visualised less consistently. Improvements in image acquisition and postprocessing techniques are expected to improve visualisation and diagnostic accuracy of the technique.


Keywords: electron beam computed tomography; coronary angiography; coronary anatomy; volume rendering     

Comparison of vessel diameters in electron beam tomography and quantitative coronary angiography

Electron beam tomography (EBT) has been shown to permit non-invasive imaging of the coronary arteries after intravenous injection of contrast agent and 3-dimensional reconstruction. We compared the vessel diameters in EBT reconstructions to quantitative coronary angiography (QCA). 10 patients were investigated by EBT and QCA. 3-dimensional EBT reconstructions (shaded surface display) were performed after acquisition of 40 axial cross-sections of the heart with 3 mm slice thickness (1 mm overlap) which were obtained triggered to the ECG in breathhold following intravenous injection of 120–160 ml of contrast agent. A fixed lower reconstruction threshold of 80 HU was used to selectively visualize the contrast-enhanced coronary artery lumen. At 60 sites in the coronary artery system, the vessel diameters measured in the EBT reconstructions were compared to the diameters found in quantitative analysis of the patients' coronary angiograms. The correlation coefficient of the vessel diameters in EBT and QCA was 0.83. Mean vessel diameters were not significantly different in EBT and QCA (3.06±0.93 vs. 2.97±0.94 mm). However, very small vessel diameters tended to be underestimated in the EBT reconstructions, which was due to the partial volume effect. If only vessel diameters measured in the left main or left anterior descending coronary artery were compared to QCA, the correlation increased to 0.87, since these vessel segments are less prone to artifacts in the EBT investigation. Vessel diameters in EBT and QCA correlate reasonably well. Due to partial volume effects, the diameter of very small vessels and stenotic segments tends to be underestimated by EBT.     

Non-invasive assessment of coronary Palmaz-Schatz stents by contrast enhanced electron beam computed tomography

The aim of the study was the evaluation of electron beam computedtomography as a non-invasive method to localize coronary stentsand to document patency in stented vessel segments. METHODS: Twenty-two patients (16m/6f, 58 ± 7·8 years) withcoronary Palmaz-Schatz stents were examined. Contrast enhancedelectron beam computed tomography using an Evolution scanner(Siemens) and coronary angiography were carried out within 7days of each other. Stent localization was performed using thesingle-slice mode of the electron beam computed tomography scanner.Patency of the coronary target segment was assessed using themulti slice mode after peripheral venous injection of a 40 mlbolus of contrast medium (Ultravist 370). Qualitative imageanalysis of a cine loop of 10 consecutive frames and quantitativeanalysis of densitometric curves in a region of interest distalto the stented vessel segment were performed. RESULTS: All stented vessel segments were identified. In 20 patients(91%), qualitative assessment of contrast enhancement patternsenabled stent patency to be evaluated. In 18 patients (90%),contrast medium was visualized distal to the stent. Quantitativecoronary angiography confirmed that the stented vessel segmentswere not stenosed. Densitometric curves obtained in 16 of these18 patients yielded contrast enhancement distal to the stentedvessel segment of 63 ± 6% compared to the aorta. In onepatient, qualitative and quantitative analysis showed prolongedcontrast enhancement of reduced density, which hinted at a stenosisrelated to the stented vessel segment. Coronary angio graphyrevealed subtotal occlusion of the stented vessel directly distalto the stent. In another patient, no contrast visualizationof the vessel distal to the stent was achieved. Coronary angiographyrevealed complete stent occlusion in this case. CONCLUSION: Electron beam computed tomography can reliably localize coronarystents and may become a useful tool for providing informationon stented vessel segment patency. (Eur Heart J 1996; 17: 1546–1553)     

Dual-phase contrast-enhancement multislice computed tomography imaging for the assessment of elderly patients with acute myocardial infarction after primary percutaneous coronary intervention

Background Evaluation of acute myocardial infarction after reperfusion by dual phase contrast-enhancement multislice computed tomography (MSCT) was implicated in porcine model. There have been few attempts to use this diagnostic modality for the early assessment of coronary reperfusion in patients with ST-elevation myocardial infarction (STEMI), especially after primary percutaneous coronary intervention (PCI). In elderly patients with STEMI, the safety issues remain unknown. Methods Dual phase contrast-enhancement MSCT examinations were performed in 11 elderly patients (≥60 years old) with STEMI within one week after primary PCI. The presence, location and enhancement pattern on MSCT were evaluated. MSCT findings were compared with the catheter angiographic results and area under the curve of creatine kinase (CK) release. Serum creatinine level was recorded before and after MSCT scan. Results MSCT scans were successfully performed in all the patients. Early myocardial perfusion defect (early defect, ED) was detected in all of the 11 patients (100%) in the early phase of the contrast bolus (subendocardial ED in 10 patients and transmural in 1 patient). Mean CT attenuation value of ED was significantly different from CT attenuation value of remote myocardium (46±17 HU vs 104 ± 17 HU; P < 0.01). Location of ED area correlated well with infarction related artery territory on catheter angiography in all of the 11 patients (100%). On delayed phase of MSCT scan, different enhancement patterns were observed: isolated subendocardial late enhancement (LE) in 6 patients, subendocardial residual perfusion defect (RD) and subepicardial LE in 1 patient, subendocardial RD in 4 patients. Infarct volume assessed by MSCT correlated well with area under the curve CK release (R=0.72, P < 0.01). Serum creatinine level after MSCT scan showed no difference with that before MSCT scan. Conclusion Dual phase MSCT could be safely implicated in elderly patients with STEMI. Variable abnormal myocardial enhancement patterns were seen on dual phase MSCT in these patients with STEMI after primary PCI. Assessment of myocardial attenuation on MSCT gives additional information of the location and extent of infarction after reperfusion.     

冠状动脉正常的急性Q波性心肌梗死单中心回顾性分析

目的 回顾性分析冠状动脉正常的急性Q波性心肌梗死患者的临床特点.方法 选取中山大学孙逸仙纪念医院确诊为急性心肌梗死,合并心电图病理性Q波形成,并经冠状动脉造影证实冠状动脉正常的患者17例,分析其临床特点.结果 本研究中,4例患者有自发性冠状动脉痉挛,表现为冠状动脉造影时严重狭窄但冠状动脉内给予硝酸甘油后狭窄消失.1例女性患者既往有下肢动脉栓塞病史,经血液系统进一步检查证实为蛋白C缺乏症.1例患者为粒细胞增多症,3例患者为血小板增多症.另有1例患者有肺癌病史,考虑可能与肺癌相关的高凝状态有关.急性Q波性心肌梗死但罪犯冠状动脉正常的患者占同期急性心肌梗死患者比例为1.85％（17/918）.此类患者平均年龄为44.2岁,男性为主,占88.2％（15/17）,吸烟比例高达82.4％（14/17）,其中吸烟患者中男性达92.9％（13/14）,与非冠状动脉正常的急性Q波性心肌梗死患者比较,差异有统计学意义（P＜0.01）.急性Q波性心肌梗死但罪犯冠状动脉正常的患者左心室射血分数显著高于冠状动脉造影异常组（54.4％±9.6％ vs.45.8％±8.8％,P＜0.01）.另外,造影正常组所有患者住院期间均未发生主要心血管事件,而造影异常组主要心血管事件发生率为6.7％（60/901）.结论 急性心肌梗死但冠状动脉正常患者以男性为主,多有吸烟史,同时合并有血液系统疾病者较多见,但大部分心功能状态良好,住院期间未见严重主要心血管事件.     

Normal coronary arteries are rare in young patients with acute myocardial infarction.

OBJECTIVE: To delineate the angiographic extent of coronary atherosclerosis in young patients (<45 years) with acute myocardial infarction (MI). BACKGROUND: Prior studies suggest 20% of young patients with acute MI have normal coronary arteries. However, most such studies defined "normal" as absence of stenoses >50% luminal diameter, ignoring the presence of nonflow limiting disease that may harbor culprit plaques. METHODS: We retrospectively analyzed 131 patients <45 years old with ST-segment elevation MI undergoing emergency catheterization. Angiograms were analyzed for the presence and extent of disease, including lesion "complexity" indicative of plaque instability. "Normal" vessels were defined as absence of any disease. RESULTS: Mean patient age was 40 +/- 7 years. The infarct related artery and an obvious complex culprit lesion was identified in all (100%) cases (left anterior descending 44%, right coronary 38%, and circumflex 18%). Single vessel disease involving the culprit vessel only was identified in 60% of cases, whereas additional disease was found in 40% of others (two-vessel in 29% and three-vessel disease in 11% of patients). CONCLUSION: These findings demonstrate that young patients with acute MI typically manifest an identifiable complex culprit atherosclerotic coronary lesion. Furthermore, they often have multivessel atherosclerosis.     

Coronary angiography by computed tomography: coronary imaging evolves

Rapid technological advances have facilitated high-resolution noninvasive coronary angiography using multislice computed tomography. Appropriateness guidelines recently have been published in the Journal of the American College of Cardiology and endorsed by several imaging specialty societies. Clinical studies are now available supporting the use of this method in selected diagnostic situations, particularly when the exclusion of coronary artery disease is of paramount clinical concern.     

Incidence and clinical relevance of coronary calcification detected by electron beam computed tomography in heart transplant recipients.

BACKGROUND: Patients treated by cardiac transplantation who survive beyond one year are at significant risk from fatal coronary artery disease. The development of coronary artery calcification in these patients is discussed and methods available to detect it are reviewed. OBJECTIVES: To assess the clinical importance of coronary artery calcium in heart transplant recipients. METHODS: In a cohort of 102 cardiac transplant recipients, electron beam computed tomography was used to measure calcium in the coronary arterial wall 63 days to 9.1 years (median 4.6 years) after transplantation. The results were compared with angiographic findings and with conventional coronary disease risk factors. The patients were followed for a mean of 2.12 years (1.2-4.02 years) to assess the relationship between these findings and future cardiac events. RESULTS: Forty-one (40.2%) had a stenosis of > 24% in one or more major coronary artery at angiography. Forty-six (45%) had a coronary calcium score > 0. The absence of calcium had a negative predictive value with respect to angiographic disease in any vessels of 87.5%. Logistic regression revealed that dyslipidaemia, systemic hypertension and organ ischaemic time were significant predictors of calcification. At follow-up, both an abnormal coronary angiogram and coronary calcium were found to be the only significant predictors of late events. Multivariate analysis suggested that the detection of coronary calcium did not offer any additional predictive information over that provided by the angiogram itself. CONCLUSION: Electron beam computed tomography is well suited to the assessment of calcium in the coronary arteries of heart transplant recipients, although the mechanisms of this calcification remain poorly understood. Calcium is detected more frequently than would be suggested by studies using intravascular ultrasound. It is associated with the presence of angiographic disease, and with some conventional risk factors for coronary disease. At follow-up the presence of coronary calcium was associated with an adverse clinical outcome, as it is in conventional ischaemic heart disease.     

Validation of minimally invasive measurement of myocardial perfusion using electron beam computed tomography and application in human volunteers

OBJECTIVES: To measure myocardial perfusion using an estimate of intramyocardial vascular volume obtained by electron beam computed tomography (EBCT) in an animal model; to assess the feasibility and validity of measuring regional myocardial perfusion in human volunteers using the techniques developed and validated in the animal studies. METHODS: Measurements of myocardial perfusion with EBCT employing intravenous contrast injections were compared with radioactive microsphere measurements (flow 57 to 346 ml/100 g/min) in seven closed chest dogs. Fourteen human volunteers then underwent EBCT scans using intravenous contrast injections. RESULTS: Mean (SEM) global intramyocardial vascular volume by EBCT was 7.6 (1.1)%. The correlation between global EBCT (y) and microsphere (x) perfusion was y = 0.59x + 15.56 (r = 0.86) before, and y = 0.72x + 6. 06 (r = 0.88) after correcting for intramyocardial vascular volume. Regional perfusion correlation was y = 0.75x + 23.84 (r = 0.82). Corresponding improvements in agreement between the two techniques were also seen using Bland-Altman plots. In the human subjects, mean resting global myocardial flow was 98 (6) ml/100 g/min, with homogeneous flow across all regions. In 10 of these subjects, perfusion was studied during coronary vasodilatation using intravenous adenosine. Global flow increased from 93 (5) ml/100 g/min at rest to 250 (19) ml/100 g/min during adenosine (p < 0.001), with an average perfusion reserve ratio of 2.8 (0.2). Similar changes in regional perfusion were observed and were uniform throughout all regions, with a mean regional perfusion reserve ratio of 2.8 (0.3). CONCLUSIONS: Accounting for intramyocardial vascular volume improves the accuracy of EBCT measurements of myocardial perfusion when using intravenous contrast injections. The feasibility of providing accurate measurements of global and regional myocardial perfusion and perfusion reserve in people using this minimally invasive technique has also been demonstrated.     

Electron beam computed tomography: screening for coronary artery disease.

The need to detect coronary atherosclerosis early in its course has been well recognized by clinicians and epidemiologists for decades. The ability to identify populations with a greater prevalence of coronary disease prior to manifestation of illness would greatly reduce cardiac morbidity and mortality. Electron beam computed tomography (EBCT) uniquely combines the characteristics of speed and excellent density resolution that have led to a rebirth of interest in detecting coronary calcium as a means of screening asymptomatic populations for coronary atherosclerosis. Electron beam computed tomography is noninvasive and widely applicable. It can both detect and quantitate the presence of coronary atherosclerosis. A positive test has diagnostic and prognostic significance, predicting future cardiac events and the extent of atherosclerosis, including the probability of obstructive coronary artery disease (CAD). Multiple studies demonstrate a 6- to 35-fold increased risk of developing a cardiac event with elevated calcium scores. A negative test is highly predictive for excluding obstructive CAD. The cost ranges from $300 to $400, similar to that of an exercise treadmill test. Moreover, scanning for coronary calcium does not require injection of contrast medium, requiring no patient preparation or exercise; therefore, a CT technician can perform the study without supervision. The entire procedure takes < 10 min to perform. These features make EBCT a potential screening test for occult CAD in symptomatic and asymptomatic persons.     

Acute myocardial infarction in patients with normal coronary arteries after acute ethanol intoxication

Three cases are presented where acute myocardial infarction occurred in young individuals after an episode of heavy alcohol intake. Subsequent coronary arteriograms demonstrated normal coronary arteries. Several mechanisms by which acute ethanol intoxication might precipitate myocardial infarction are discussed. To our knowledge, no similar cases have been reported.     

Correlation of coronary angiography with "tombstoning" electrocardiographic pattern in patients after acute myocardial infarction

BACKGROUND: It has been suggested that a specific pattern of electrocardiographic (ECG) changes following acute myocardial infarction (AMI), the so-called "tombstoning," predicts a poorer outcome, although the cause and associations of such changes are not known. To address the possible cause and implications, we correlated angiographic findings with tombstoning in patients following AMI. METHODS: The study investigated 124 patients with AMI, whose ECGs were taken within 24 h of onset of symptoms and who subsequently underwent angiography. In this population, 24 (19%) patients had a definite tombstoning pattern on their admission ECG. RESULTS: Compared with non-tombstoning ECGs, the significant differences in the tombstoning group are as follows: (1) All patients, including those with inferior infarction, had either total or partial occlusion of the left anterior descending (LAD) artery (100 vs. 44%, p < 0.0001); (2) LAD occlusions were significantly more severe and mostly proximal (100% occlusion: 50 vs. 20.5%, p = 0.02; <50% occlusion: 0 vs. 15.9% p = 0.039; proximal occlusion: 92 vs. 65%, p = 0.017); (3) patients with tombstoning ECGs had a significantly greater incidence of occlusion of all three coronary arteries (54.1 vs. 22%, p = 0.001); (4) tombstoning ECGs were more strongly associated with anterior than with inferior infarction (83.3 vs. 33%, p < 0.0001). CONCLUSIONS: The patients with a tombstoning pattern on the admission ECG, who underwent angiography, were associated with occlusion of a high-grade stenosis of the proximal LAD artery (usually with involvement of more than one artery) and were predominantly seen in association with anterior infarction.     

冠状动脉钙化与急性心肌梗死的关系简

目的 探讨冠状动脉钙化与急性心肌梗死之间的关系.方法 22 537例患者中,男13 204例,女9 333例,年龄（58.53±9.48）岁,共有急性心肌梗死患者2 254例.依据冠状动脉造影术中能否发现冠状动脉钙化分为钙化组（A组）和无钙化组（B组）,统计两组间心肌梗死发病率的区别,并探讨其原因.结果 钙化组心肌梗死患病率明显高于无钙化组,差异有统计意义（18.16％vs.8.84％,P＜0.001）;钙化组较无钙化组男性多见（62.46％ vs.58.04％,P＜0.001）、年龄偏大[（64.61±7.92）岁vs.（57.67±9.37）岁,P＜0.001];糖尿病（25.64％ vs.15.28％,P＜0.001）、原发性高血压（高血压）发病率高（74.00％vs.57.13％,P＜0.001）;易发生血管病变（93.70％ vs.7.32％,P＜0.001）,且以多支血管病变为主.即使在心肌梗死患者中,钙化组血管病变的发生率及多支血管病变所占比例也超过非钙化组,差异有统计意义（99.61％vs.94.32％,P＜0.05;91.18％ vs.66.23％,P＜0.05）.两组均以ST段抬高型急性心肌梗死为主,两组心肌梗死部位比较,差异无统计学意义（P＞0.05）.结论 冠状动脉钙化患者,男性多见、年龄偏大;糖尿病、高血压发病率高;易发生血管病变,容易导致心肌梗死.     

Coronary computed tomography angiography and its increasing application in day to day cardiology practice

Coronary artery disease (CAD) is the leading single cause of death in Australia affecting around 1.4 million people. Coronary computed tomography angiography has an established role in the assessment of patients with low to intermediate pretest probability for CAD who have chest pain and is typically used with the aim to rule out significant coronary artery stenosis. Use was initially limited because of concerns over radiation exposure, a Medicare rebate restricted to specialist referrals and an absence of data supporting its use as an alternative to functional testing in patients with chest pain. Recent advances in scanner technology and image sequencing, along with data from randomised control trials, have addressed these issues and indicate that coronary computed tomography angiography will play a greater role in the assessment of CAD in the coming years.     

双源计算机断层扫描成像在冠状动脉小血管支架内再狭窄的应用价值

目的探讨双源计算机断层扫描冠状动脉造影术(dual source computed tomography coronary angiography,DSCT-CA)在冠状动脉小血管支架内再狭窄的应用价值。方法对76例(男59例,女17例)有胸闷、胸痛的患者在术后6～12个月行经皮冠状动脉造影后行DSCT-CA检查。根据心率及造影结果将患者分成不同的组别:心率≤70次/min组[n=48,扫描时心率(58±5)次/min]与心率﹥70次/min组[n=41,扫描时心率(78±9)次/min];简单病变组(单个支架,n=54)与复杂病变组(重叠支架及分叉支架,n=35);右冠状动脉组(n=33)、左回旋支组(n=43)和左前降支组(n=13),并比较分析DSCT-CA对各组诊断的敏感性、特异性及阳性预测值、阴性预测值。结果76例患者共植入89个支架,其中31.4%(28/89)的支架经血管造影证实有再狭窄。DSCT-CA对支架内再狭窄的敏感性、特异性及阳性预测值、阴性预测值分别为89%、87%、76%和95%。DSCT-CA对心率≤70次/min组与心率﹥70次/min组的诊断价值比较,差异无统计学意义(P>0.05)。DSCT-CA对冠状动脉三主支的诊断价值比较,差异也无统计学意义(P>0.05)。DSCT-CA诊断复杂病变组的敏感性、阳性预测值、特异性,阴性预测值均低于简单病变组,差异有统计学意义(83%vs.94%,P<0.05;63%vs.88%,P<0.05;74%vs.95%,P<0.05;89%vs.97%,P<0.05)。简单病变组组内分析结果显示,其敏感性和特异性比较,差异无统计学意义(94%vs.95%,P>0.05);阳性预测值低于阴性预测值,差异有统计学意义(88%vs.97%,P<0.05)。4年的质控分析结果显示,DSCT-CA检测小血管支架内再狭窄率呈逐年上升趋势,2006年及2007年再狭窄率均在平均水平以下,2009年超出了平均水平的一倍。结论DSCT-CA可作为小血管支架术后再狭窄的筛选手段,阴性者可排外支架内再狭窄,阳性者需进一步行冠状动脉造影以明确诊断。     

Radiation dose difference between state of the art myocardial perfusion scintigraphy and computed tomography coronary angiography in patients undergoing evaluation for suspected coronary artery disease

Minimisation of radiation exposure with cardiac imaging reduces the potential of secondary side effects. Radiation exposure from myocardial perfusion scintigraphy and computed tomography coronary angiography (CTCA) was compared. Overall doses were low with both modalities. Doses were lower in the CTCA group, but by only a small difference of 1.1 mSv. Radiation exposure should not be the primary consideration when choosing between these two modalities.