|Year : 2015 | Volume
| Issue : 4 | Page : 113-119
Multislice CT coronary angiography is an additional tool for provisional diagnosis of acute chest pain with neither ECG nor echocardiography significant findings in emergency room
Hanan K Kassem1, Naglaa L Dabees2, Ayman A El-Sheikh1, Mohamed S Hegab3, Rasha M Dawoud MD 2, Hend M Mansour4
1 Department of Cardiology, Faculty of Medicine, Tanta University, Tanta, Egypt
2 Department of Radiodiagnosis, Faculty of Medicine, Tanta University, Tanta, Egypt
3 Mahalla Cardiac Center, Mahallah, Egypt
4 Department of Emergency and Traumatology, Faculty of Medicine, Tanta University, Tanta, Egypt
|Date of Submission||19-May-2015|
|Date of Acceptance||29-Jul-2015|
|Date of Web Publication||30-Oct-2015|
Rasha M Dawoud
Department of Radiodiagnosis, Faculty of Medicine, Tanta University Hospital, Tanta University, Hassen Radwan Street, 31512, Tanta
Multislice coronary computed tomography (CT) angiography is used to diagnose coronary artery disease (CAD) with good spatial and temporal resolution.
The aim of this study was to assess the uses of thin-slice multidetector row CT in the diagnosis of different vascular coronary causes of chest pain.
Patients and methods
A total of 20 patients were examined with full history taking, resting 12-lead ECG, cardiac biomarkers, and echocardiography. Thereafter, on the basis of their clinical manifestations or suspected progression of past condition they were enrolled for 160-multislice CT angiography using Ultravist 370 as a contrast medium.
CT coronary angiography revealed the following: two cases were normal, two showed nonsignificant CAD, three showed significant CAD, 10 showed mild-to-moderate CAD, two showed anomalous coronary arteries, and one showed myocardial bridge.
CT angiography nowadays is considered the primary tool of diagnosis for different thoracic vascular disorders, being a safe, rapid method of diagnosis. Multislice coronary CT is a relatively new technique that gives physicians the advantage of screening emergency patients presenting with acute chest pain in a rapid and safe way for detection of their vascular diseases.
Keywords: computed tomography angiography, coronary artery disease, multidetector computed tomography
|How to cite this article:|
Kassem HK, Dabees NL, El-Sheikh AA, Hegab MS, Dawoud RM, Mansour HM. Multislice CT coronary angiography is an additional tool for provisional diagnosis of acute chest pain with neither ECG nor echocardiography significant findings in emergency room. Tanta Med J 2015;43:113-9
|How to cite this URL:|
Kassem HK, Dabees NL, El-Sheikh AA, Hegab MS, Dawoud RM, Mansour HM. Multislice CT coronary angiography is an additional tool for provisional diagnosis of acute chest pain with neither ECG nor echocardiography significant findings in emergency room. Tanta Med J [serial online] 2015 [cited 2020 Dec 1];43:113-9. Available from: http://www.tdj.eg.net/text.asp?2015/43/4/113/168724
| Introduction|| |
Triage of patients with acute, potentially life-threatening chest pain is one of the most important issues currently physicians are facing in the emergency department. Appropriate evaluation of these patients begins with a skilled assessment of the patients' presenting symptoms and a careful review of their history and physical examination, often followed by serial recording of ECGs and measurement of serum biochemical markers such as troponin and D-dimer. Stress testing, often accompanied by rest and stress myocardial perfusion imaging or echocardiography, and other diagnostic tests such as radionuclide lung scanning and invasive angiography may be required. A rapid, accurate, and cost-effective approach for the evaluation of emergency department patients with chest pain is needed  .
Challenges in evaluating the coronary arteries with computed tomography (CT) are the small size of the vessels and their location adjacent to the moving heart. The vessels are typically 2-4 mm in diameter and are parallel, oblique, or perpendicular to the axial plane in sections. In addition, they are adjacent to both the atria and the ventricles and therefore may be affected by cardiac motion in different phases of the cardiac cycle  .
The development of newer generations of multidetector computed tomographic (MDCT) scanners that are capable of not only performing high-quality noninvasive coronary angiography but also performing concurrent aortic and pulmonary angiography has led to the increased use of MDCT for the so-called 'triple-rule-out'. MDCT is used for the detection of three of the most common life-threatening causes of chest pain: coronary artery disease (CAD), acute aortic syndrome, and pulmonary emboli. Although triple-rule-out protocol can be very useful and potentially cost-effective when used appropriately, concern has risen as regards the overuse of this technology, which could expose patients to unnecessary radiation and iodinated contrast. The triple-rule-out protocol is most appropriate for patients who present with acute chest pain, but are judged as having low-to-intermediate increased risk for acute coronary syndrome, and whose chest pain symptoms might also be attributed to acute pathologic conditions of the aorta or pulmonary arteries  .
Continued technical improvements in acquisition speed and spatial resolution of CT images, and development of more efficient image reconstruction algorithms, which reduces patient exposure to radiation and contrast, may result in increased popularity of MDCT for triple-rule-out  .
| Patients and methods|| |
A total of 20 patients with acute chest pain and nondiagnostic resting ECG and echocardiography and normal cardiac biomarkers were enrolled for multidetector row CT angiography of the coronary arteries between February 2014 and February 2015. The mean age of the patients was 54 ± 10.09 years, ranging from 35 to 72 years. Ten (50%) patients were male and 10 (50%) patients were female.
Patients with acute chest pain and nondiagnostic resting ECG and echocardiography and normal cardiac biomarkers were included. Atypical chest pain is defined as chest pain fulfilling any two of the three criteria defining typical chest pain. The criteria were as follows:
- Constricting discomfort in the front of the chest, or in the neck, shoulders, jaw, or arms.
- Precipitation on physical exertion.
- Relief with rest or glycryl tri nitrates (GTN) within about 5 min.
Exclusion criteria were as follows: rapid irregular heart beat (different types of arrhythmias), previous by-pass surgery or stenting, contraindications to iodinated contrast material including known allergy and renal insufficiency (serum creatinine>1.4 mg/dl), contraindications to radiation exposure (i.e. pregnancy), respiratory impairment (inability to withhold breathing), and unstable clinical status or marked heart failure.
This study was approved by the ethics committee of our institution; informed consent was obtained from all patients after full explanation of the benefits and risks of the procedure.
All patients were subjected to the following:
- Full history taking.
- Full clinical evaluation with special emphasis on risk factors for CAD, resting 12-lead well standardized ECG, and laboratory investigations including cardiac biomarkers, tests for diabetes and hyperlipidemia, as well as echocardiography.
- MDCT coronary angiography.
- Patients were asked to fast 4-6 h before the examination. Medications were not to be discontinued.
- The patients should be well hydrated for renal protection and for ease of establishing venous access.
- Patients were advised to refrain from caffeine products for 12 h before examination, including coffee, tea, energy drinks, energy pills, diet pills, and soda drinks.
- The heart rate was evaluated before the examination. The examination was carried out if the heart rate was below 65 beats/min.
- Patients with heart rates above 65 beats/min were given cardioselective β-blocker, 100 mg of atenolol orally 1 h before the study, to obtain a stable low heart rate, provided the contraindications to β-blockers are excluded.
- Nitroglycerine was not administrated before the study because, despite its coronary-dilator effect that enhances visualization, the drug has the potentiality to increase the heart rate and also falsely increases the estimated diameter reduction in the stenotic lesions.
- The steps of the study were explained in detail to each patient. To evaluate the patient's ability of breath-holding, they were required to perform a normal inspiration and to continue to hold their breath without pushing (i.e. Valsalva maneuver). During this trial, the patient was observed for compliance and the ECG for significant changes.
A bolus of 70-80 ml of water-soluble nonionic contrast (Ultravist 370, Bayer Pharma A.G, Berlin, Germany) was injected through an 18-G cannula into an upper limb vein at a flow rate of 5-5.5 ml/s; it was injected in the right antecubital vein in all our cases to reduce left-sided artifacts. Thereafter, 40-50 ml of saline was injected at a flow rate of 4 ml/s using a programmed dual-head power injector pump (Mederad) to maintain good opacification of the coronary vessels with washout of contrast material from the superior vena cava (SVC) and the right side of the heart that may cause artifacts.
CT angiographic examinations were performed using the 160-dual source MDCT (Aquilion Prime 160; Toshiba Medical Systems, Ohtawara, Japan). The protocol used: kV = 120 mA = 500 mAs = 111 slice thickness = 1 mm.
Patients were positioned supine on the CT table, and ECG leads were fixed on the chest wall. All reconstructions were performed using the retrospective ECG gating. For this technique, an ECG must be recorded simultaneously throughout the duration of the scanning.
An anteroposterior and lateral scanogram views of the examined region was taken. It was used to position the imaging volume of the coronary arteries, which extends from the level of tracheal bifurcation down to about 1 cm below the diaphragm. The center of the field of view is 2 cm to the left of the dorsal spine on the anteroposterior scout and at the level of the hilum on the lateral scout.
An initial step of noncontrast CT examination of the heart was performed for all patients to detect and quantify coronary calcifications through the volume extended from below the carina to the apex of the heart. Total calcium scores of all patients were calculated with the dedicated software and expressed as Agatston scores.
The Agatston score is a commonly used scoring method that calculates the total amount of calcium on the basis of the number, areas, and peak Hounsfield units (HU) of the detected calcified lesions. Thereafter, automated determination of the starting time using the 'bolus-tracing technique' was carried out. It entails injection of the whole volume of the utilized contrast material as a one bolus at the predetermined rate. After a delay of about 10 s from the start of injection (time estimated for the contrast to reach the great vessels of the chest, being variable according to the site of the cannula, rate of injection, body build, and heart rate), a series of axial images at the level of the origin of the left main coronary artery is acquired with an interval of 1 s between subsequent images. The density within the descending aorta is monitored in each axial image on real-time basis while the region of interest carefully avoiding the atheromatous calcifications.
Time-attenuation curves were generated. When the density within the descending aorta exceeded 120 HU (i.e. the contrast started to arrive), the scanning was triggered with a delay of further 3 s (time needed for the table movement to the cranial start position while the patient is instructed to hold breathing). This time delay also allows for increase in the contrast concentration at the ascending aorta and coronary arteries.
During the helical scan, the ECG signal was recorded digitally. Patients were instructed to maintain an inspiratory breath-hold while the CT data and the ECG trace were acquired.
For most patients, the arteries were best visualized at 75 and 40% of the cardiac cycle. If these images were not satisfying, further phases of the cardiac cycle were used to visualize the different coronary segments.
In patients with some motion artifacts, four datasets were created during different time instants of the cardiac cycle (50, 60, 70, and 80% of the R-R-wave interval). The dataset containing the fewest motion artifacts (on the bases of cross-sectional images) was used for further creation of the reconstructed images and evaluation of the coronary artery.
The reconstructed axial images at different points of the cardiac cycles were sent to an offline workstation where detailed reconstruction was made to each dataset to obtain the data.
Visibility of the coronary artery segment was considered 'good' when there was a sharp delineation from the surrounding structures, a nearly artifact-free course of the segment, with less blurring even in its peripheral sections, and sufficient contrast detected between the vessel lumen and the wall. Visualization was considered 'adequate' in the presence of image-degrading artifact that did not interfere with evaluation with moderate confidence and was considered 'poor' in the presence of image-degrading artifacts when the evaluation is possible yet only with low confidence. The examined segment was considered 'nonassessable' when the image-degrading artifacts were severe enough to prevent differentiation between the significant stenosis and occlusion on one hand and the normal segment or mildly atherosclerotic lesions on the other hand.
As regards the composition of the plaque, a distinction was made between calcified and noncalcified plaques. Plaques with a mean attenuation of 130 HU or greater were graded as calcified, whereas plaques with a mean attenuation of less than 130 HU were graded as noncalcified. Calcified plaques were identified on nonenhanced scans, and noncalcified plaques were identified on contrast-enhanced scans.
Identification of coronary artery segments was based on the model suggested by the American Heart Association [Figure 1], which divided the coronary arterial system into 15 segments.
|Figure 1: Segmental anatomy of the right coronary artery (RCA) (lateral view) and the left coronary artery (right anterior oblique view) with left main trunk (LMT), left anterior descending (LAD), and left circumflex (LCX) according to the American Heart Association .|
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| Results|| |
Multidetector row CT angiography of the coronary arteries was performed for all patients without any complications as a result of having acute chest pain. Twenty patients were included in this study (10 male and 10 female; age range, 35-72 years; mean age, 54 ± 10.09 years). In this study, the most common age group was 60 years to less than 70 years, and the least common affected age group was 30 years to less than 40 years. As regards sex, 50% of patients were male and 50% were female [Table 1].
All patients had an initial negative ECG and were also negative for cardiac biomarkers; nonsignificant changes were seen on echocardiography. For 16 (80%) cases the cause of chest pain was found on CT; however, for four (20%) cases CT was negative and needed further investigation to detect the cause of chest pain.
As regards the prevalence of diabetes mellitus, we found that, 11 (55%) cases were diabetic and nine (45%) were nondiabetic. As regards the prevalence of hypertension, nine (45%) cases were hypertensive and 11 (55%) were not hypertensive. Seven (35%) cases were smokers and 13 (65%) were nonsmokers. As regards lipid profile, we found that, 12 (60%) cases had dyslipidemia and eight (40%) cases were not. As regards family history of CAD, we found that, four (20%) cases had positive family history and 16 (80%) cases had negative family history [Table 2].
As regards calcium score, it was found to be below 800 in all examined patients and thus no patient in our study was excluded on the basis of the calcium score value. Two (10%) cases were normal, two (10%) showed nonsignificant CAD, three (15%) showed significant CAD, 10 (50%) showed mild-to-moderate CAD, two (10%) showed anomalous coronary arteries [anomalous origin of the dominant right coronary artery (RCA) from the left coronary sinus by a separate ostium from the left main trunk, the proximal RCA segment runs as interarterial course], and one (5%) showed myocardial bridge.
Plaques were seen in 13 (65%) patients, eight (40%) of them had noncalcified and five (25%) had calcified plaques.
As regards the vessel affected we found that left anterior descending (LAD) was affected in 14 (70%) cases, left circumflex was affected in four (20%), and RCA was affected in four (20%) cases. As regards the number of vessels affected, six (30%) cases were free of affection, single vessel was affected in seven (35%), two vessels were affected in six (30%), and three vessels were affected in one (5%) [Figure 2] and [Table 3] and [Table 4].
|Table 4 A significant relation between the number of risk factors and the number of vessels affected |
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A 50-year-old female patient with known diabetes, not hypertensive, no dyslipidemia, and no family history of CAD presented with attacks of atypical chest pain. A 12-lead ECG and echocardiography showed nonsignificant changes; cardiac biomarkers were negative [Figure 3].
|Figure 3: Normal multidetector computed tomography coronary angiography. LAD, left anterior descending; LCX, left circumflex; RCA, right coronary artery|
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A 61-year-old female patient with known hypertension, dyslipidemia, not diabetic, and a negative family history of CAD presented with complains of atypical chest pain. A 12-lead ECG and echocardiography showed nonsignificant changes; cardiac biomarkers were negative.
Coronary CT angiography revealed proximal LAD long noncalcified lesion causing significant stenosis, atherosclerotic CAD [Figure 4].
|Figure 4: Atherosclerotic coronary artery disease; a noncalcified lesion in the proximal left anterior descending (LAD) causing significant stenosis. LMT, left main trunk|
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A 63-year-old male patient with known diabetes, no dyslipidemia, not hypertensive, and a negative family history of CAD presented with complains of atypical chest pain. A 12-lead ECG and echocardiography showed nonsignificant changes; cardiac biomarkers were negative.
Coronary CT angiography revealed atherosclerotic CAD, noncalcified lesions in the ostial and paraostial and mid-LAD segments causing moderate stenosis, and a mildly ectatic proximal left circumflex segment [Figure 5].
|Figure 5: Noncalcified lesions in ostial and paraostial and mid left anterior descending (LAD) segments causing moderate stenosis and a mildly ectatic proximal left circumflex (LCX) segment. LMT, left main trunk.|
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| Discussion|| |
Although selective conventional coronary angiography will remain vital for planning and guiding catheter-based and surgical treatment of significantly stenotic coronary lesions or occlusions, the comprehensive and serial assessment of asymptomatic or minimally symptomatic stages of CAD for preventive purposes will eventually need to rely on noninvasive imaging techniques. Cardiovascular imaging with tomographic modalities, including CT and MRI, has great potential for providing valuable information  .
Patients with a higher pretest likelihood of CAD (>70%; e.g. with typical angina, risk factors, and a positive stress test) should not undergo coronary CT angiography as the first-line modality, because more patients in this subgroup will require subsequent coronary angiography and because the negative predictive value of CT is reduced (making a negative CT result less reliable). In contrast, the positive predictive value is rather low in patients with a very low pretest likelihood of CAD (<20%; e.g. with nonanginal chest pain and a negative stress test) and the CT findings would lead to many unnecessary conventional coronary angiographies  .
Diagnostic accuracy of multislice CT in CAD has significantly improved with the development of scanning techniques, which are demonstrated by the emergence of 16-slice, 64-slice, and even more recently 256-slice and 320-slice CT scanners  .
There has been a sharp decline in cardiovascular disease mortality, which has been mainly attributed to substantial improvements in primary and secondary prevention and medical disease management. However, the fact remains that cardiovascular disease continues to be the most important health problem globally, particularly in the westernized world  .
In this study, the pre-examination heart rate was evaluated, and patients with rate above 65 beats/min were given cardioselective β-blocker orally 1 h before the study to obtain a stable low heart rate, provided that contraindication to β-blockers is excluded. This is in agreement with the findings of Pugliese et al.  , who reported that, if the heart rate is still above 75 beats/min, the examination should be postponed to another setting.
In the present study, which enrolled 20 patients, we found that, two (10%) cases were normal, two (10%) cases showed nonsignificant CAD, three (15%) cases showed significant CAD, 10 (50%) cases showed mild-to-moderate CAD, two (10%) cases showed anomalous coronary arteries, and one (5%) case showed myocardial bridge. Single-vessel disease was detected in seven (35%) patients, a two-vessel disease in six (30%), and a three-vessel disease in one (5%).
In a study carried out by Shabestari et al.  , which enrolled 65 participants giving a history of atypical chest pain, 42 (64.6%) had no CT-angiographically detectable coronary artery lesion, eight (12.3%) patients had nonsignificant lesions, and 15 (23.1%) had significant stenosis. Of the 15 patients with significant CAD, a single-vessel disease was shown in 12 (18.5%) patients, a two-vessel disease in two (3.1%), and a three-vessel disease was seen in one (1.6%)  .
| Conclusion|| |
Our results showed that noninvasive 160-slice CT coronary angiography is a reliable technique to detect coronary stenosis in patients presenting with acute chest pain and suggest that this noninvasive technique can now be considered an alternative to invasive diagnostic coronary angiography in such patients.
However, we should know the practical limitation of the CT protocol:
Financial support and sponsorship
- β-blockers, which are required for coronary computed tomography angiography, may not be safe in patients with pulmonary embolism;
- lack of experienced technologists and physician supervision;
- obesity and calcifications limit interpretation; and
- incidence of rapid heart rate, arrhythmias, renal dysfunction and contrast allergies.
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3], [Table 4]