2009, Cilt 22, Sayı 3, Sayfa(lar) 197-202
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INCIDENTAL DETECTION OF CORONARY ARTERY CALCIFICATIONS ON NON-CARDIAC THORACIC CT EXAMINATIONS
Kadriye Orta Kılıçkesmez1, Özgür Kılıçkesmez2, Neslihan Taşdelen2, Duygu Kara2, Yüksel Işık2, Arda Kayhan3, Bengi Gürses2, Nevzat Gürmen2
1İstanbul Üniversitesi Kardiyoloji Enstitüsü, Kardiyoloji, İstanbul, Türkiye
2Yeditepe Üniversitesi, Radyoloji, İstanbul, Türkiye
3Namık Kemal Üniversitesi, Radyoloji, Tekirdağ, Türkiye
Keywords: Multidetector computed tomography, Heart, Coronary calcification
Abstract
Objective A strong relationship have been demonstrated between the presence of occlusive coronary artery disease and coronary artery calcifications detected at autopsy, fluoroscopy, or computed tomography (CT). The aim of our study was to evaluate the frequency of incidental coronary artery calcifications during thoracic CT examinations and to correlate them with cardiac risk factors.

Materials and Methods: Thoracic CT scans obtained over a pereiod of6 months from 113 patients (72 male and 41 female) with a mean age of 62,7 (31-92 years) were retrospectively evaluated. The thoracic scans were performed using standard 9 mm consecutive slices from the apex to the base of the thorax, using a standard thoracic protocol, on a Siemens 16 channel multislice CT scanner. Coronary arteries were evaluated for calcifications.

Results: Thirty-seven patients (32.7%) had coronary calcifications.18 patients (15.9%) had one, 9 patients (7.9%) had two, 7 patients (6.2%) had three, and 3 patients (2.6%) had four with vessel calcifications. The frequency of coronary calcifications was correlated with hypertension, diabetes mellitus, hypercholesterolemia, nicotine abuse, and cardiomegaly. Diabetes mellitus, hypercholesterolemia, cardiomegaly and male gender were significantly associated with coronary calcifications (p<0.05).

Conclusion: With the advent of multislice faster CT scanners, coronary artery calcifications are more frequently and easily detected during non-cardiac thoracic CT examinations. This retrospective study showed an increased incidence of coronary calcifications in patients with cardiac risk factors. Among these factors diabetes mellitus, hypercholesterolemia, cardiomegaly and male gender were statistically significant.

  • Top
  • Abstract
  • Introduction
  • Methods
  • Results
  • Disscussion
  • References
  • Introduction
    The presence of coronary artery calcification is a significant indicator of atheromatous disease and it may indicate the presence of severe stenosis. While the absence of calcification does not correlate with the absence of coronary artery disease, an incidental finding of calcium has important prognostic implications. Most of the previous work documenting calcification has been observed in patients with a known history of heart disease undergoing further cardiac investigations1,2.

    Early diagnosis of atherosclerosis is therefore highly important in predicting and preventing myocardial infarction. Imaging modalities especially CT scans have been proved to be quite helpful1. The aim of this study was to evaluate the frequency of incidental coronary artery calcifications during thoracic CT examinations, and to correlate with cardiac risk factors.

  • Top
  • Abstract
  • Introduction
  • Methods
  • Results
  • Disscussion
  • References
  • Methods
    Thoracic CT scans obtained over a period of 6 months from 113 patients (72 male and 41 female) with a mean age of 62,7 (31-92 years) were retrospectively evaluated. The exclusion criteria were existing implanted coronary stents, a history of previous bypass surgery, or non-diagnostic scans with poor resolutions. Thoracic scans were performed using standard 9 mm consecutive slices from the apex to the base of the thorax, using a standard thoracic protocol, on a Siemens 16 channel multislice CT scanner. A standard sof tissue window was used (WL: 50, WW: 500) for the assessment of slices.

    The coronary arteries were evaluated for calcifications. The number and location of coronary calcifications were noted for each patient. The investigated cardiac risk factors were gender, hypertension, diabetes mellitus, hypercholesterolemia, and nicotine abuse. The diagnosis of cardiomegaly was achieved with the calculation of transverse heart ratio (>0,5) on thoracic x-rays.

    Medical records were reviewed and the data related to age, sex, smoking history, risk factors for vascular disease, and general medical condition were noted in a standardized form. Previous cardiac disease was determined on the basis of : electrocardiographic evidence of arrhytmias, ischemia or previous myocardial infarction. Prior infarctions were documented by evaluation of enzyme levels, history of angina or congestive heart failure treatment, and findings of any available studies of cardiac function such as cardiac echocardiography, exercise thallium myocardial perfusion imaging and exercise tolerance testing.

    Image interpretation
    CT scans were transferred to an independent Workstation (Leonardo console, software version 2.0; Siemens) for postprocessing, and the 3D multiplanar reconstruction (MPR) images were reconstructed in the coronal and sagittal planes in addition to the axial source slices. The left anterior descending (LAD), circumflex and right coronary arteries (RCA) were evaluated for presence of calcifications by two radiologists on the basis of the knowledge of the CT anatomy of the coronary arteries. in consensus. The readers were experienced in reading images of the coronary anatomy. The presence of coronary calcifications was evaluated with a contiguous-slice method. A calcified lesion was defined as a hyperdense area inside the artery with a Hounsfield unit (HU) of greater than 90 and that measured 0.5 mm2 or larger.

    Statistical Analysis
    All statistical analysis were performed using SPSS (Statistical Package for Social Sciences) for Windows 10.0. The number of calcifications, locations, and the risk factors of the patients were reported as the mean ± standard deviation. Student’s t test was performed to compare the subgroups with and without calcifications. A p value of less than 0.05 was considered to indicate a statistically significant difference.

  • Top
  • Abstract
  • Introduction
  • Methods
  • Results
  • Disscussion
  • References
  • Results
    A total of 113 thoracic CT scans were reviewed. The scans were performed with various clinical indications. The most common indication was for identification of primary or secondary lung carcinomas, followed by airway disease evaluation.

    Thirty-seven patients (32.7%) had coronary calcifications. Of the 37, 18 patients (15.9%) had one 9 patients (7.9%) had two, 7 patients (6.2%) had three, and 3 patients (2.6%) had four vessel calcifications (left main coronary, circumflex, LAD and RCA).

    The incidence of calcifications were significantly higher in males (p<0.05), as well as in patients with diabetes mellitus (12.3%), hypercholesterolemia (16.8%) and cardiomegaly (20.3%) (p<0.05). Although nicotine abuse, and hypertension are associated with increased risk of calcification, these were not statistically significant. (Table-I).


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    Table I: Association of cardiac risk factors with coronary calcifications.


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    Figure 1: Axial thorax CT image at the level of heart demonstrates left main coronary and circumflex artery calcifications.


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    Figure 2: Coronal 3D MPR CT image of the thorax at the level of heart demonstrates left main, anterior descending and circumflex coronary artery calcifications.

  • Top
  • Abstract
  • Introduction
  • Methods
  • Results
  • Disscussion
  • References
  • Discussion
    Autopsy studies have shown that there is a close link between coronary artery calcification and the extent of vascular stenosis with a subsequent risk of myocardial infarction. A variety of imaging modalities has been used for detecting coronary artery calcifications of which, plain chest radiography and fluoroscopy have the lowest sensitivity. CT imaging is superior to fluoroscopy for detecting coronary calcifications1.

    Ultrafast CT has high-resolution contrast, a rapid image acquisition, and allows elimination of image blurring caused by heart movement. Due to these features, ultrafast CT has a high sensitivity for detecting calcium in the coronary arteries3. In different series, the sensitivity and specificity of the examination ranged from 88 to 100% and 43 to 100%, respectively2,4,5.

    Arterial calcification occurs in the intima of the blood vessels, as a part of atherosclerosis. In general population, coronary artery calcification correlates with the atherosclerotic plaque burden and with coronary vessel stenosis, and has consistently been shown to be predictive for future cardiac events6-9.

    Coronary segments with a luminal obstruction greater than 50% are likely to have some calcification that is detectable with electron-beam CT. In a trial, it was shown that, a 0 calcium score had a 100% predictive value in the exclusion of angiographic evidence of obstructive epicardial coronary lesions. The higher the calcium score, the more likely the presence of angiographic obstructive disease10.

    Results of autopsy studies indicate that coronary artery calcification is invariably associated with the presence of atherosclerotic plaque11. In a previous study performed with 450 consecutive patients, Callaway et al found atherosclerotic plaques in 26% of male and 15.6% of female scans. The incidence increased to 48% from 41.6% when they have determined a threshold of 40 years for age12.

    Coronary calcification is strongly associated with the prognosis. Indeed, the extent of coronary atherosclerosis (total calcium score) is the most powerful predictor of subsequent or recurrent cardiac events. This was true in the former years when calcium was detected with fluoroscopy and conventional CT13.

    Janowitz et al., analyzed the evolution of the amount of calcium in atherosclerotic plaques by ultrafast CT in patients with and without coronary artery disease3. Ninety-eight percent of the calcium deposits identified on the initial examination were confirmed in consequent imagings, and there was a significant increase in the calcification volume and in the total calcified area of the atherosclerotic plaque in the evolution. Patients with coronary artery disease have a large amount of new calcium deposits, which are not found in asymptomatic patients. In patients with no evidence of calcification, both in the first approach and later, the prevalence of ischemic heart disease is extremely low.

    In a study searching the presumptive detection of coronary stenosis on the basis of existing calcification by means of CT, higher sensitivities have been found in the calcified arteries (78% for LAD, 63% for the circumflex and 16% for RCA). Specificities were 78%, 80% and 100%, and positive predictive values (PPV) were 88%, 83% and 100%, respectively. The high PPV suggested that significant coronary artery disease was likely to be present when coronary calcification was seen on CT14. In a study performed by Shirazi et al,, of the total 100 patients (62 males), 69 had coronary artery obstruction (>50% stenosis was detected by angiography). Angiography was normal in the rest. For the diagnosis of coronary artery disease, a spiral CT scan had a sensitivity of 94% and a specificity of 61%. PPV and negative predictive value (NPV) were 84% and 79%, respectively1.

    In their series performed with double-helix CT, Shemesh et al., stated that calcification was significantly more prevalant in patients with coronary artery obstructive disease (>83%) than in patients with normal coronary arteries (27%) or in healthy control subjects (34%, p<0.1). The researchers found a high sensitivity (91%), however, the specificity was low (52%) due to calcification in non-obstructive lesions15. When CT and angiographic findings were compared, CT was found to have 84% accuracy with PPV and NPVof 89% and 59%, respectively15.

    In contrast, some investigators claim that the technique is useless16. Detrano et al., in their series performed with 1196 asymptomatic high-coronary-risk subjects that underwent risk-factor assessment and cardiac CT, showed that CT calcium score did not add significant incremental information to risk factors in clinical screening. The researchers claimed that neither risk-factor assessment nor the calcium detected with CT was an accurate event predictor in high-risk asymptomatic adults16.

    Our study had some limitations. Our sample size was small and a relatively old CT technology was used. Moreover, there was no gold standard angiographic demonstration of stenotic effects of the calcium deposits.

    In conclusion, coronary calcifications were easily discernible with CT. Our study showed that calcified deposits were more frequently encountered with increasing age and male gender. In addition, to the increased association of coronary calcification with the male gender, a relationship to diabetes mellitus, hypercholesterolemia and cardiomegaly was detected.

    Acknowledgement:
    There was no financial support for this study.

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  • Abstract
  • Introduction
  • Methods
  • Results
  • Discussion
  • References
  • References

    1) Shirazi AS, Nasehi N, Sametzadah M, Saberi H, Shabani MA. Spiral CT scan for detecting coronary artery stenosis. Iran. J Radiol 2005; 3:11-15.

    2) Feldman C, Vitola D, Schiavo N. Detection of coronary artery disease based on the calcification index obtained by helical computed tomography. Arq Bras Cardiol 2000;75:471-480.

    3) Janowitz WR, Agatston S, Kaplan G, Viamonte M. Differences in prevalence and extent of coronary artery calcium detected by ultrafast computed tomography in asymptomatic men and women. Am J Cardiol 1993; 72: 247-254.

    4) Tanenbaum SR, Kondos GT, Veselick KE, Prendergast MR, Brundage BH, Choomka EV. Detection of calcific deposits in coronary arteries by ultrafast computed tomography and correlation with angiography. Am J Cardiol 1989; 63: 870-871.

    5) Wong ND, Abrahamson D, Tobis JM, Eisenberg H, Detrano RC. Detection of coronary artery calcium by ultrafast computed tomography and its relation to clinical evidence of coronary artery disease. Am J Cardiol 1994; 73: 223-227.

    6) Wexler L, Brundage B, Crouse J, et al. Coronary artery calcification: Pathophysiology, epidemiology, imaging methods, and clinical implications. A statement for health professionals from the American Heart Association. Writing Group. Circulation 1996; 94:1175–1192.

    7) Keelan PC, Bielak LF, Ashai K, et al. Long-term prognostic value of coronary calcification detected by electron-beam computed tomography in patients undergoing coronary angiography. Circulation 2001; 104:412– 417.

    8) Budoff MJ. Prognostic value of coronary artery calcification. JCOM 2001; 8:42–48.

    9) Greenland P, LaBree L, Azen SP, et al. Coronary Artery Calcium Score combined with Framingham Score for risk prediction in asymptomatic individuals. JAMA 2003; 291:210–215.

    10) Rumberger JA, Brundage BH, Rader DJ. Electron beam computed tomographic coronary calcium scanning: a review and guidelines for use in asymptomatic persons. Mayo Clin Proc 1999;74:243-252.

    11) McNamara JJ, Molot MA, Stremple JF, Cutting RT. Coronary artery disease in combat casualties in Vietnam. JAMA 1971; 216: 1185-1187.

    12) Callaway MP, Richards P, Goddard P, Rees M. The incidence of coronary artery calcification on standard thoracic CT scans. Br J Radiol 1997; 70: 572-574.

    13) Selby JB, Morris PB. Coronary Artery Calcification – CT. url:http://emedicine.medscape.com/article/352189-overview

    14) Timins ME, Pinsk R, Sider L, Bear G. The functional significance of calcification of coronary arteries as detected on CT. J Thorac Imaging 1991;7:79-82.

    15) Shemesh J, Apter S, Rozenman J, et al. Calcification of coronary arteries: detection and quantification with double-helix CT. Radiology 1995;197:779-783.

    16) Detrano RC, Wong ND, Doherty TM, et al. Coronary calcium does not accurately predict near-term future coronary events in high-risk adults. Circulation. 1999 May 25;99:2633-2638.

  • Top
  • Abstract
  • Introduction
  • Methods
  • Results
  • Discussion
  • References
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