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Hindi Research Article, Int J Cardiovasc Res Vol: 1 Issue: 5
Noninvasive Coronary Artery Calcium Scoring: Do We Always Need Invasive Computed Tomographic Angiography for Diagnostic Purposes?
| Mojgan Sametzadeh1, Habib Haybar1*, Mehran Saiahy1, Ahmad Ahmadzadeh3, Mohammad Davoodi1, Atefeh Yoosefi4, Ahmadreza Assareh2 and Seyed Mohammad Hasan Adel2,5 | |
| 1Radiology Group, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran | |
| 2Cardiovascular Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran | |
| 3Hematology Ward, Golestan Hospital, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran | |
| 4Internal Medicine Ward, Shiraz university of Medical Sciences, Shiraz, Iran | |
| 5Prevention of Metabolic Disorders Research Center, Research Institute for Endocrine Sciences, Shahid Beheshti University of Medical Sciences, Tehran, Iran | |
| Corresponding author : Habib Haybar Cardiovascular Research Center, Golestan Hospital, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran, P.O. Box: 173 Tel: 0098-611-3743019; Fax: 0098-611-3743019 E-mail: dr.habibhaybar@yahoo.com |
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| Received: November 19, 2012 Accepted: November 29, 2012 Published: December 07, 2012 | |
| Citation: Sametzadeh M, Haybar H, Saiahy M, Ahmadzadeh A, Davoodi M, et al. (2012) Noninvasive Coronary Artery Calcium Scoring: Do We Always Need Invasive Computed Tomographic Angiography for Diagnostic Purposes?. Int J Cardiovasc Res 1:5. doi:10.4172/2324-8602.1000111 |
Abstract
Noninvasive Coronary Artery Calcium Scoring: Do We Always Need Invasive Computed Tomographic Angiography for Diagnostic Purposes?
The coronary artery disease (CAD) epidemic has emerged in the developing countries during the past two to three decades. It, however, has attracted less comment and little public health response, even within these countries. At present, developing countries are not widely recognized to contribute a greater share to the global burden of CAD than the developed countries. The most common cause of CAD is atherosclerosis.
Keywords: Calcium score; Multi-slice computed tomography; Coronary artery stenosis; Coronary heart disease; CT angiography
Keywords |
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| Calcium score; Multi-slice computed tomography; Coronary artery stenosis; Coronary heart disease; CT angiography | |
Introduction |
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| The coronary artery disease (CAD) epidemic has emerged in the developing countries during the past two to three decades. It, however, has attracted less comment and little public health response, even within these countries. At present, developing countries are not widely recognized to contribute a greater share to the global burden of CAD than the developed countries [1]. The most common cause of CAD is atherosclerosis [2]. Atherosclerotic advanced plaques have a large amount of calcium. Quantitative measurement of coronary calcium as a marker of atherosclerotic coronary disease and predictors of the risk factor for ischemic heart disease during the past twenty years has been agreed and approved [3-5]. Method such as chest radiography, fluoroscopy, and conventional computed tomography (CT), are used for coronary calcification determination [6,7] but Electron beam computed tomographic coronary calcium scanning (EBCT) and multi-slice spiral computed tomography (MSCT) are used for quantitative measurements [8-13]. The most common method for grading the extent of coronary calcification is Agatston scoring, in which the total size and density of calcific deposit can be assessed [14]. Electrocardiography, echocardiography, review perfusion of myocardium by Technetium-99m stress-rest SPECT myocardial perfusion imaging (MPI), positron emission tomography (PET), CT scan, magnetic resonance imaging (MRI), CT Angiography (CTA) with contrast, and invasive angiography were among the methods used in the detection of significant coronary stenosis. Protests imaging coronary include significant stenosis of more than 50% diameter or more than 70% luminal surface of heart coronary vessels [3]. Despite recent advances, CT Angiography is still the most definitive instrument in diagnosis and evaluation of coronary vessels anatomy. Current generation multi-detector-row CT (MDCT) enables high-resolution, motion-free imaging of the heart within a single, short breath-hold [15]. | |
| We sought in the current study to examine the concordance of the calcium score with CT angiography in rating participants’ coronary artery stenosis severity. We also compared the diagnostic performances of the calcium score with those of the CT angiography as a gold standard for detection of stenosis. | |
Materials and Methods |
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| Study population | |
| Data were analyzed on 412 participants (222 males and 190 females) consecutively registered at Golestan and Emam Hospitals, Ahvaz, Iran. All participants had nonanginal symptoms and were referred for noninvasive CT angiographic study of coronary arteries. The enrollment started at April 2010 and terminated at October 2011. Participants were excluded if they self-reported history of coronary artery bypass graft and/or prior stent placement, allergic reaction to contrast agent were observed to have arrhythmia or renal failure (Cr >1.5 mg.ml-1), or if they were unable to hold their breath for at least 10 seconds. | |
| Measurements | |
| Demographic data was secured using a predetermined questionnaire. The measurements were performed using a 64-channel MSCT scanner (SOMATOM Sensation 64, Siemens Medical, Germany). | |
| Coronary CT protocol | |
| Heart rates were measured one hour before examination. Oral premedication included a beta-blocker, for calcium scoring (using a scanner with rotation times <370ms) was not necessary, but because of using CT Angiography for results comparison, the average heart rate was higher than 70 beats per minute (bit.min-1), they would receive an oral beta-blocker of 50-100 milligrams of Metoprolol (Alborzteb, Tehran, Iran), to obtain rates of 65 bit.mim-1 or less. We first ensured that the patient had no contraindications to beta-blocker, such as asthma, atrioventricular block, obstructive airway disease, low cardiac output states, or severe left ventricular dysfunction. Participants were instructed to abstain for 12 hours from all products containing caffeine. | |
| Images were obtained with synchronously Electrocardiography (ECG)-gated spiral scanning. Scanning was performed from tracheal carina down to the apex of the heart, using retrospective ECG-gated reconstruction temporal window settings at 60% of the ECG peak of consecutive R waves (R-R interval). Scanning parameters for calcium-scoring series were Collimation, 1.2 mm; table speed, 5.8 mm.rotation-1; slice width, 3 mm; pitch, 0.2; rotation time, 0.33 sec; 190 mAs, and 120 KV and for the contrast enhanced series (CTA) were as follows: Collimation, 64*0.6 mm; table speed, 3.8 mm/rotation; slice width, 0.6 mm; pitch, 0.2; rotation time, 0.33 sec; 770 mAs, and 120 KV. | |
| A bolus of 120-140 milliliter of a nonionic contrast medium (Ultravist 320 mgI.ml-1, Schering, Berlin, Germany) was administered via an 18-gauge cannula through an antecubital vein at a rate of 5 ml.s-1. Bolus-tracking (CARE Bolus) with continuous aortic monitoring was used to determine scanning start time. Scan data for continuous volume images of the entire heart, based on 3 mm slice-width and strongly overlapping increment could be acquired within 10-12 seconds. Three-dimensional reconstructions with about 0.6 mm slice width and submillimeter increment provided data of adequate quality for visualization of the coronary arteries. The estimated radiation dose for the calcium score protocol was 1.4 (0.6 mSv) and the estimated average radiation dose for the coronary angiography protocol was 18.1(5.9) mSv. | |
| Analysis of CT image | |
| Calcium score was calculated by Syngo software, on a Wizard workstation (Siemens Medical Solutions), Erlangen, Germany for the total coronary artery territory and for right coronary artery (RCA), left circumflex artery (LCx), left anterior descending artery (LAD) and left main coronary artery (LMCA), individually. We used Agatston calcium scoring method for the aforementioned major coronary arteries, both integrally and independently [14]. Coronary artery calcification was defined as the presence of at least 3 mm adjacent pixels with a CT-number of at least 130 Hounsfield Units (HU). In each slice, all calcifications along a coronary artery were manually confined as a region of interest and the volume of calcium deposit and the number of all marked calcified lesions were then automatically measured and recorded by the Calcium Score module of Syngo software. | |
| CTA images were reconstructed in the 3D and Vessel View modules of the Syngo software and evaluated with multiplanar reconstruction (MPR), curved-MPR, thin maximum intensity projection (MIP), and volume rendering technique (VRT) reformats. Two radiologists interpreted the images together and a general consensus was achieved in all cases. | |
| Definition of terms | |
| Nonanginal chest pain was defined as chest discomfort with only 1 of the characteristics of typical angina (retrosternal component, Brought on by stress or exercise, relieved promptly by rest or nitroglycerin). | |
| Applying Agatston score, participants were classified as normal (calcium score, 0), having non-significant coronary artery stenosis (calcium score, 5-10), or having significant coronary artery stenosis (calcium score, 10 or more). | |
| Using CTA participants were classified as normal (no stenosis), having non-significant coronary artery stenosis (<50% stenosis), or having significant coronary artery stenosis (≥ 50% stenosis). | |
| Statistical analysis | |
| Data are presented as either mean (SD) or frequency (%) for continuously- and categorically-distributed variables, respectively. Agreement between to calcium score and CT angiography in rating severity of stenosis was measured using Cohen’s Kappa. We also computed following diagnostic measures and their 95% confidence intervals (95% CIs) to compare calcium score with CT angiography as a gold standard: sensitivity, specificity, positive and negative likelihood, and positive and negative predictive value. | |
| It is certified that all applicable institutional and governmental regulations concerning the ethical use of human volunteers were followed during this research. Informed written consent was obtained from all participants and the Ethical Committee of Research Institute for Endocrine Sciences approved this study. The study protocol conforms to the ethical guidelines of the 1975 Declaration of Helsinki. | |
| The statistical significance level was set at a two-tailed type I error of 0.05. All statistical analyses were performed using STATA version 12 (STATA, College Station, Texas USA). | |
Results |
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| The mean age of the participants was 49.5 (28.5) years (age range 21 to 78 years). The calcium scoring and CT-Angiography examination was not interpretable in 4 participants. Reasons for non-interpretability were the presence of motion artifacts, increased noise due to high body mass index, and breathing. As such, we analyzed data on a total of 412 participants. | |
| Using calcium score 236 participants (57.3%) were classified as normal, 25 participants (6.0%) as having non-significant coronary artery stenosis, and 151 participants (36.7%) as having significant coronary artery stenosis. | |
| During MSCTA image acquisition, an average heart rate of 65(7) beats per minute was recorded. CT-angiography classified 252 participants (61.2%) as normal, 50 participants (12.1%) as having non-significant stenosis (<50% luminal narrowing), and 110 participants (26.7%) as having significant stenosis (≥ 50% luminal narrowing). | |
| Tables 1 and 2 show the cross-tabulation of calcium scoring against CTA scoring of coronary artery stenosis, as sex-pooled and sex-specific. In general there was a 89.6% agreement between calcium score and CTA (Cohen’s kappa = 0.752, P value <0.001). The corresponding figure was 90.9% (Cohen’s kappa = 0.783, P value =<0.001) and 88.1% (Cohen’s kappa = 0.715, P value <0.001), among men and women, respectively. | |
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Table 1: Cross-tabulation of degrees of coronary artery stenosis rated by calcium score agains computed tomographic angiography. |
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Table 2: Cross-tabulation of degrees of coronary artery stenosis rated by calcium score against computed tomographic angiography, by sex. |
| Calcium score achieved sensitivity of 0.90 (95% CIs: 0.84-0.94), specificity of 0.87 (95% CIs: 0.83-0.91), positive likelihood ratio of 7.09 (95% CIs: 5.11-9.84), negative likelihood ratio of 0.12 (95% CIs: 0.07-0.18), positive predictive value of 0.82 (95% CIs: 0.75-0.87), and negative predictive value of 0.93 (95% CIs: 0.89-0.96) for diagnosis of the significant CTA-detected coronary artery stenosis. | |
Discussion |
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| We documented an excellent agreement between calcium score and CTA in stratifying patient with different degrees of coronary artery stenosis. We also demonstrated that calcium score scores of 0-5 confer excellent diagnostic performances for significant coronary artery stenosis. | |
| Because calcium score scans are fast, offer low radiation dose, and predict cardiovascular events, they are frequently performed before MDCT angiography in the clinical setting. We observed no evidence to reject the hypothesis that low calcium score can safely rule out significant (>50%) coronary stenosis. This finding held across sexes. Thus calcium score, thus, can be suggested to be used as a gatekeeper for angiographic studies in nonanginal participants with suspected CAD. High sensitivity and negative predictive value would render calcium score a useful screening tool in this regard. Such a screening approach would help patient avoid iodinated contrast and increased ionizing radiation exposures, the complications of invasive angiography, high cost, and psychiatric stress. | |
| Two thirds of all coronary catheter examinations in the US are merely performed for verifying the presence and degree of coronary artery disease CAD [16] and have only diagnostic implication. Thus, a reliable, non-invasive tool for imaging of the coronary arteries and for early diagnosis of coronary artery disease is highly desirable [17]. Clinical usefulness of the CT coronary artery calcium scoring stems from the fact that calcium is an early marker of atherosclerosis and arterial calcification almost always represents atherosclerosis [18]. Similarly, several initial studies have demonstrated high negative predictive value of calcium scoring for exclusion of significant coronary artery disease in patients with acute chest pain [19-21] which has been approved in recent prospective studies [22]. | |
| Cademartiri et al. have shown that calcium scoring is more beneficial among asymptomatic persons as compared to symptomatic ones [23]. | |
| Our findings give support to the notion that he calcium score is usually measured in asymptomatic participants with intermediate risks for coronary artery events. It has been consistently shown that a low calcium score in this subgroup suggests a low risk of coronary events in 5 to 10 years [4,24,25]. | |
Strength and Limitations |
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| The strength of our study lies in its ability to examine sex-specific diagnostic properties of calcium scoring. Our findings, however, should be interpreted in the context of its limitations. We were not able to take the effects of established CAD risk factors into account. We, therefore, were not able to examine if calcium scoring can help improve diagnostic performances of risk algorithm currently used to predict CAD. Cross-sectional nature of the study does not allow us to make any interpretation on the long-term predictive performance of the calcium scoring for CAD event. | |
Conclusion |
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| We documented an excellent agreement between calcium score and CTA in stratifying patient with different degrees of coronary artery stenosis. We also demonstrated that calcium score of 0-5 confer excellent diagnostic performances for significant coronary artery stenosis. High sensitivity and negative predictive value would render calcium score a useful screening tool for CAD events. In the light of the fact that the calcium scoring scan is fast and not invasive, we suggest it to be used as primary screening tool for CAD events in order to avoid high cost, psychiatric stress iodinated contrast and increased ionizing radiation exposures, as well as other complications of invasive angiography. | |
Acknowledgment |
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| Our special thanks go to members of Golestan Hospital Clinical Development Research Center and Molook Salemzadeh for helping us in data collection. The authors would like to thank Caroline Kheradmand for her assistance in language-editing of the manuscript. | |
References |
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