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Multi-slice CT and Coronary Artery Disease
- Arpan K Banerjee (21 May 2003)
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Motivational interviewing or EBCT to raise compliance?
- Bo Christensen, Sune Rubak (12 June 2003)
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Coronary Artery Calcification Scoring
- Mark CK Hamilton, Chris J Occleshaw (17 June 2003)
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Arpan K Banerjee, Consultant Radiologist Birmingham Heartlands Hospital, B9 5SS
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Dear Sir I read the editorial entitled "Finding the age of the Patient's heart" with interest.[1] Anand et al discuss the role of electron beam computed tomography in detecting early coronary atherosclerosis. Their discussion did not mention the role of multislice computed tomography in detecting stenoses and imaging of non stenotic plaques. Multislice CT using 4 detectors still has significant improved resolution in the Z plane compared with electron beam CT angiography in which only ECG triggered 3mm slices can be obtained. MDCT enables 1mm slices and sub millimetre image increments to provide a 3 dimensional data set in a single breath hold for high resolution CT volume imagaging. [2,3] There are several studies now present using non invasive MDCT angiography to assess stenotic lesions in the coronary arteries with sensitivities above 70% and specificities of above 80%. [3,4] Limitations of this technique include calcified vessels which themselves make assessment of the coronary arteries more difficult. In addition the heart rate above 80 beats per minute can make visualisation difficult. These may be less of a problem with the new 16- channel multi-detector CT technology which has recently been introduced into clinical practice.[5] Although electron beam CT can be used to assess calcification and plaques in the coronary arteries, I feel that the newer technoogy of a multi-slice CT scan, which is now becoming more widely available, will result in a better non invasive screening tool for coronary artery disease. Yours sincerely Dr Arpan K Banerjee
REFERENCES 1. Anand DV, Lipkin D, Lahiri A. Finding the age of the patient's heart. BMJ 2003 326 1045-1046 2. Herzog C, Ay M, Engelmann K et al. Visualisierungs-modalitaten in der Multidetektor CT-Koronarangiographie des Herzen: Korrelation von axialer, multiplanarer, dreidimension-aler und virtuell endoskopischer Bildgebung mit der invasiven Diagnostik. Fortschr Rontgenstr 2001; 173: 341-59 3. Kopp AF, Schroder S, Kuttner A et al. Coronary arteries: retrospectively ECG-gated multi-detector row CT angiography with selective optimization of the image reconstruction window. Radiology 2001; 221: 683-8 4.Kopp AF, Schroder S, Kuttner A et al. Non-invasive coronary angiography with high resolution multidetector-row computed tomography: results in 102 patients. Eur Heart J 2002; 23: 73-84 5. Flohr T, Bruder H, Becker CR et al. Isotropic sub-millimeter volume scanning of the heart with ECG-gated multislice spiral CT: First experience. Eur Radiol 2002; 12: S217 Competing interests: None declared |
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Bo Christensen, Associate Professor, PhD, M.D., G.P Department of general Practice, University of Aarhus. Vennelyst Boulevard 6, DK-8000 Aarhus C, Denma, Sune Rubak
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Dear Sir In the editorial "Finding the age of the Patient's heart" Anand et al discuss the role of electron beam computed tomography (EBCT) to identify patients with an increased risk for coronary heart disease by detecting early coronary atherosclerosis, but also EBCT as a possibility to improve compliance with treatment of lipid lowering drugs, which is a major issue[1].” Could EBCT bridge these gaps effectively?” Anand asks. It is a major problem that patients do not benefit from evidence based treatment because of poor compliance. However, is it necessary to use technology such as EBCT to raise the compliance? The motivational interviewing is evolved from experiences in the treatment of problem drinkers. The basic experiences were developed by Miller and Rollnick (1991) into a coherent theory and detailed description of clinical procedures[2] . Miller and Rollnick defined motivational interviewing “as a directive, client-centred counselling style for eliciting behaviour change by helping clients to explore and resolve ambivalence”. Motivational interviewing is a particular way to help clients recognize and do something about their present or potential problems. Motivational interviewing is particularly useful with clients who are reluctant to change behaviours or ambivalent about changing. The strategies of motivational interviewing are more persuasive than coercive, and more supportive than argumentative. The overall goal is to increase the client’s intrinsic motivation, so that changes arise from within rather than being imposed from without[2]. Motivational interviewing has been investigated in relation to a broad area of problem behaviours and diseases with positive effects which are also shown in relation to overweight, hyperlipidemia and lack of physical activity [3,4]. We hope there will be more focus on motivational interviewing in the future than on the use of cost full technology in order to raise compliance. Yours sincerely Bo Christensen References 1.Anand DV, Lipkin D, Lahiri A. Finding the age of the patient's heart. BMJ 2003;326:1045-6. 2.Miller WR, Rollnick S. Motivational interviewing, preparing people to change addictive behavior. New York: The Guildford Press, 72 Spring Str., NY 10012, www.guildford.com, 2002. 3.Beresford SA, Curry SJ, Kristal AR, Lazovich D, Feng Z, Wagner EH. A dietary intervention in primary care practice: the Eating Patterns Study. Am.J.Public Health 1997;87:610-6. 4.Harland J, White M, Drinkwater C, Chinn D, Farr L, Howel D. The Newcastle exercise project: a randomised controlled trial of methods to promote physical activity in primary care. BMJ 1999;319:828-32. Competing interests: None declared |
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Mark CK Hamilton, Fellow in Cardiac Radiology Department of Cardiology, Green Lane Hospital, Greenlane West, Auckland 3, New Zealand, Chris J Occleshaw
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EBCT and Coronary Calcification Editor - We read the editorial by Anand et al with interest.1 Electron beam computed tomography (EBCT) is a fascinating technology. However the use of coronary artery calcification (CAC) scoring is highly controversial. The presence of calcification in a coronary artery does not indicate the presence of an obstructive lesion or the position of any such lesion that may exist. As the authors state patients with symptoms of coronary ischaemia, supported by evidence of myocardial ischaemia on a treadmill test or stress imaging study, require imaging of the coronary artery lumen. This is to ascertain the number, distribution and severity of obstructive coronary lesions present, prior to revascularisation by PTCA or coronary bypass surgery as appropriate. At the present time, the only technique able to perform such luminal imaging is an invasive coronary angiogram, although rapid developments in multislice CT (MSCT) technology in recent years may make CT coronary angiography of an adequate standard possible in certain patient groups in the near future. The paper by Raggi et al quoted by the authors suggesting that EBCT is more cost effective than a stress test is flawed in that amongst other problems it ignored the cost of purchasing the scanner (several million pounds). 2 Furthermore the quoted study of cost effectiveness was performed in North America and does not necessarily apply to countries with different cost structures. 3 In view of the limitations of CAC scoring described above, it is hard to see what diagnostic or therapeutic advantage there is for the symptomatic patient in having the amount of calcification in their coronary arteries measured. There is one study examining the use of CAC scoring in patients with atypical chest pain presenting to hospital, which demonstrated that the absence of calcium in the coronary arteries was associated with a very low risk of an acute coronary event, and thus allowed for immediate discharge. 4 This data was obtained before the widespread use of serum troponin measurements, and thus may not be relevant now. The use of CAC scoring in the screening of asymptomatic individuals for the presence of coronary artery disease is worth more discussion. The prevention of coronary artery disease, and treatment of existing disease, includes a number of lifestyle changes and appropriate medical therapies. These include cessation of smoking, the attainment of adequate exercise and appropriate dietary habits, plus management of diabetes, hypercholesterolaemia, hypertension and obesity. We are aware of no evidence that CAC scoring alters any of the above treatment aims, or that the guidelines for appropriate management of such conditions require knowledge of the patient's CAC score. In addition, there is no evidence that assessing the effectiveness of such treatments requires the measurement of coronary artery calcification. However we do acknowledge that a picture is worth a thousand words, and that compliance (and hopefully outcome) may be improved in those patients who are shown a picture of abnormality in their own coronary arteries. This is yet to be demonstrated. The appropriate use of any screening technique requires a number of conditions to be met, as laid out by the World Health Organisation. 5 The authors have overlooked one great problem with CAC scoring which is that there are a large number of false positive results, especially in older males, in whom some degree of coronary calcification is almost invariable in western societies – as shown in Agatston’s original paper describing the technique. 6 The majority of such individuals will never have symptomatic coronary disease. The use of CAC scoring risks such individuals being referred for a number of further investigations, including invasive coronary angiography, for no good reason. This is an inappropriate use of scarce healthcare resources, and not without some risk to the patient (there remains a small but significant morbidity and mortality with coronary angiography). In their excellent review of EBCT, Thomson and Hachamovitch state that; “there are no well conducted studies that clearly demonstrate the incremental value of calcium scoring over traditional assessments of risk factors, and the clinical role of EBCT is yet to be established in terms of screening for disease or risk assessment.” 7 They authors state that a CAC score with EBCT involves a radiation dose equivalent to only 2 chest radiographs. The majority of CAC scoring is likely to be performed with MSCT due to the widespread availability of these scanners (EBCT scanners are far more expensive and have limitations in other imaging use: as far as we are aware there are none in Australasia). A standard PA CXR involves an effective radiation dose to the patient of 0.02 - 0.04 mSv 8,9 An audit by an independent radiation physicist of 2 modern CT scanners performing CAC scores in Auckland in 2001 measured an effective dose between 1.5 and 2.2 mSv. 10 We accept that there is reduced dose for EBCT compared to MSCT, but find the implied effective dose of 0.04 - 0.08 mSv for an EBCT study unlikely. Unfortunately, the authors fail to give any measure of dose, or details of radiographic factors and technique, so their claim cannot be scrutinised. A single dose of 2 mSv to an individual is a very small risk, but a screening programme would require large numbers of the population to be exposed to such a dose on repeated occasions, and thus the population risk grows in importance. It is impossible to justify such a risk when to date there has been no clearly demonstrable benefit. Mammography is an important precedent for the use of a screening test involving the use of radiation in the general population. This became available in most western countries after numerous studies established rigorous quality standards, produced recommendations for the appropriate age of subjects to be screened, the interval between screenings, and demonstrated effectiveness in both detecting disease and in reducing mortality. 11,12,13 They also examined the costs in terms of the healthcare resources required. None of this information is established for CAC scoring, and will not be for some time yet, due to the lack of published results from any large trials involving the thousands of subjects required for a number of years. In Australia (but not New Zealand), this lack of information has not prevented CAC scoring becoming widely available over the last decade in both cardiology and radiology private practices, many of which are now owned by multinational companies. There was a great deal of initial enthusiasm for the technique amongst referring clinicians and the public, who were encouraged by widespread direct advertising in all forms of media. Unfortunately unrealistic claims were made by some; an example being that one screening episode was enough to exclude coronary artery disease for life. It would be most unfortunate if this were to be repeated in the UK because of the undoubted commercial benefits possible, both from performing the examination itself, and from the possibility of self- referral for further investigations of those individuals with a high CAC score. We note that as yet no major academic cardiology organisations recommend CAC scoring, and indeed that the AHA/ACC Consensus document on the technique came out strongly against its use, suggesting that it is no more effective than other existing techniques. 14 We also note that whereas screening mammography is available in many western countries as part of a publicly funded health service, no country provides CAC scoring, despite the far greater prevalence of coronary artery disease compared to breast cancer. We believe that there is as yet no justification for the use of CAC scoring as a screening technique for the presence of asymptomatic coronary artery disease in the general population, except as part of a large multicentre trial, approved by the relevant ethical committees. We do welcome further investigation of its value, and await the results of those trials currently under way in Europe and the USA with considerable interest. M C K Hamilton MRCP(UK), FRCR. Cardiac Radiologist C J Occleshaw MRCP(UK), FRCR. Cardiac Radiologist Dept. of Cardiology, Green Lane Hospital, Greenlane West, Auckland 3, New Zealand 1. Anand DV, Lipkin D, Lahiri A. Finding the age of the patient’s heart. Electron beam computed tomography detects early coronary atherosclerosis. BMJ 2003;326:1045-6 2. Raggi P, Callister TQ, Cooil B et al. Evaluation of chest pain in patients with low to intermediate pretest probability of coronary artery disease by electron beam computed tomography. Am J Cardiol 2000;85:283-288 3. Rumberger JA, Behrenbeck T, Breen JF, Sheedy PF 2nd. Coronary calcification by electron beam computed tomography and obstructive coronary artery disease: a model for costs and effectiveness of diagnosis as compared with conventional cardiac testing methods. J Am Coll Cardiol 1999;33:453-62. 4. Georgiou D, Budoff MJ, Kaufer E et al. Screening patients with chest pain in the emergency department using electron beam tomography: a follow up study. J Am Coll Cardiol. 2001;38:105-110 5. Wilson JMG, Jungner YG. Principles and practice of screening for disease. Public Health Papers No. 34. Geneva, World Health Organisation 1968. 6. Agatston AA, Janowitz WR, Hildner FJ et al. Quantification of coronary artery calcium using ultrafast computed tomography. J Am Coll Cardiol 1990;15:827-32 7. Thomson LEJ and Hachamovitch R. Coronary artery calcium scoring using electron beam computed tomography: where does this test fit into clinical practice? Rev Cardiovasc Med. 2002;X(X):XX-XX 8. Food and Drug Administration. www.fda.gov/cdrh/ct/risks.html 9. Code of practice for the use of x-rays in medical diagnosis. National Radiation Laboratory C5 1994. Ministry of Health, New Zealand 10. F.Thompson, personal communication. 11. Tabár L, Fagerberg CJG, Gad A, Baldetorp L, Holmberg LH, Gröntoft O, et al. Reduction in mortality from breast cancer after mass screening with mammography. Randomised trial from the Breast Cancer Screening Working Group of the Swedish National Board of Health and Welfare. Lancet 1985; i: 829-832. 12. Department of Health and Social Security. Breast cancer screening. Report to the Health Ministers of England, Wales, Scotland & Northern Ireland by a working group chaired by Professor Sir Patrick Forrest. London: HMSO, 1986. 13. Blamey RW, Day NE, Young JR et al. The frequency of breast cancer screening: results from the UKCCCR randomised trial. European Journal of Cancer 38 (2002) 1458-1464 14. O’Rourke RA, Brundage BH, Froelicher VF et al. American College of Cardiology/American Heart Association expert consensus document on electron beam computed tomography for the diagnosis and prognosis of coronary artery disease. Circulation.2000;102:126-40 Competing interests: None declared |
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