EDITORIAL

CT angiography of the coronary arteries

NE KLØW

Department of Cardiovascular Radiology, Ulleval University Hospital, Oslo, Norway

Non-invasive coronary imaging using spiral CT has

the potential to replace conventional coronary an-

giography. However, with the fast evolving technol-

ogy the enthusiasm may be well ahead of the present

documentation. ‘‘Requiring little more than an

injection of x-ray contrast through an IV placed in

the arm, the CT angiography allows physicians to

view even the smallest of arteries of heart’’ (1).

The technique

Multislice (MSCT) or multi detector (MDCT) CT

scanners may be used to assess the coronary lumen

and the coronary plaques including calculation of

the amount of calcium. Most of the documentation

of the performance has been from the 4-slice and the

16-slice scanners. Simultaneous acquisition of sev-

eral slices per gantry rotation can be obtained using

multislice scanners hence the total scan time can

be reduced. By having a shorter scan time the

patient may be able to hold their breath during the

whole scanning. The scan time for 4-slice scanner is

35�/40 s and approximately 20 s for 16-slice scanner.

The motion of the heart and the fact that the heart

movement varies during the cardiac cycle requires

ECG synchronization, usually retrospective gating.

Recently, 64-slice scanners have been available, with

faster rotation and improvement of the software to

process the images (2).

Compared to conventional coronary angiography

there are some concerns. The radiation exposure

with MDCT is higher than that of invasive angio-

graphy. The effective radiation dose during conven-

tional coronary angiography varies between 3 and

10 mSv, with 4-slice MDCT it is 6�/13 mSv, with

16-slice 8�/11 mSv and with 64-slice 7�/11 mSv. It is

expected that radiation exposure will come down

with improved protocols and radiation-saving scan-

ning (2,3). The volume of full strength contrast

medium is high, approximately 100 ml. The ne-

phrotoxicity may add further risk to the patients with

reduced kidney function, in particular if the patient

is sent for angioplasty within a few days.

The performance

Both the image interpretability and the diagnostic

performance are related to the scanners, protocols of

included patients, severity of coronary disease,

calcium score and previous stents, use of beta-

receptor blockers, scan protocols and data analysis.

In 4-slice scanners approximately 25% of segments

had to be excluded from analysis because of poor

image quality, and in 16-slice, close to 10%. Using

16-slice MDCT reported sensitivity to detect 50%

diameter reduction was 82�/100% and specificity

84�/100%. Recent publications of 64-slice scanners

indicate further improvement in both interpretability

and diagnostic performance (4�/6). In vitro studies of

stents have shown that the visualization of stent

lumen was superior with 64-slice compared to 16-

slice (7). Also, patients with atrial fibrillation may be

examined (8).

Clinical indication

There are still problems with new scanners regarding

patients with arrhythmias, high calcium score and

previous stents. Patients with arrhythmias and stents

may, however, be excluded on beforehand. If an

initial calcium score is done first, the scanning of the

coronary lumen may be cancelled when the score is

high. There are no established algorithms for using

the MDCT. Potential indications are early detection

Correspondence: Ne Kløw, Hjerte-karradiologisk avdeling, Ulleval Universitetssykehus, N-0407 Oslo. E-mail: n.e.klow@medisin.uio.no

Scandinavian Cardiovascular Journal. 2006; 40: 69�/70

(Received 2 March 2006; accepted 2 March 2006)

ISSN 1401-7431 print/ISSN 1651-2006 online # 2006 Taylor & Francis

DOI: 10.1080/14017430600669882

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of stenosis in patients from high-risk families, in

those with atypical chest pain, refractory chest pain

with doubtful coronary origin, and non-conclusive

stress test. MDCT may replace coronary angiogra-

phy in patients with aortic disease and prior to major

non-cardiac surgery. Considering the fast develop-

ment of the machines and improvement of the image

analysis programs, it is important that independent

groups evaluate their programs early when this new

modality is taken into use in clinical practice.

In this issue Rødevand et al. (9) have evaluated

16-detector MSCT in 157 elective patients with

suspected coronary artery disease. In 56 patients

(36%) the study was non-assessable for evaluation,

in most patients because of the MSCT. In the 101

patients with interpretable MSCT angiograms an-

other 21% of the segments could not be assessed.

The authors concluded ‘‘Limited diagnostic accu-

racy, non-interpretable scans and radiation exposure

restrict the usefulness of coronary MSCT in a

community hospital setting.’’ Bartnes et al. (10)

prospectively compared 16-detector MDCT and

conventional angiography of coronary artery bypass

grafts. Forty five patients were included within three

years after bypass surgery. In 38 (24%) of 156 grafts

the MDCT angiograms were not assessable. Evalu-

ating patency, significant stenosis and occlusion of

each graft, the MDCT wrongly classified seven (6%)

of 117 assessable grafts. The authors concluded ‘‘At

present, 16-slice MDCT cannot replace selective

angiography for assessment of coronary bypass graft

patency’’. Findings and conclusions are important,

and are a strong signal to evaluate the results before

MDCT is applied as a general diagnostic tool of

coronary artery disease.

In conclusion, at this point 64-slice CT scanners

have the potential to replace conventional coronary

angiography in many patients. Further improvement

of diagnostic performance is, however, required and

expected. Major concerns are high radiation dose to

the patients, high contrast medium load in patients

with reduced kidney function, and low diagnostic

performance in calcified arteries, after stenting and

in patients with arrhythmias. Which patients should

primarily be scheduled for MDCT, is not known yet.

References

1. Aurora Health Care, Wisconsin. http://www.aurorahealthcare.

org/services/radiology/64-slice.asp.

2. de Feyter PJ, Krestin GP. Computed tomography of the

coronary arteries. London: Taylor and Francis; 2005.

3. Stein PD, Beemath A, Kayali F, Skaf E, Sanchez J, Olson

RE. Multidetector computed tomography for the diagnosis of

coronary artery disease: A systematic review. Am J Med.

2006;/119:/203�/16.

4. Leschka S, Alkadhi H, Plass A, Desbiolles L, Grunenfelder J,

Marincek B, et al. Accuracy of MSCT coronary angiography

with 64-slice technology: First experience. Eur Heart J. 2005;/

26:/1482�/7.

5. Mollet NR, Cademartiri F, van Mieghem CA, Runza G,

McFadden EP, Baks T, et al. High-resolution spiral computed

tomography coronary angiography in patients referred for

diagnostic conventional coronary angiography. Circulation.

2005;/112:/2318�/23.

6. Pugliese F, Mollet NR, Runza G, van Mieghem C, Meijboom

WB. Malagutti P, et al. Diagnostic accuracy of non-invasive

64-slice CT coronary angiography in patients with stable

angina pectoris. Eur Radiol. 2006;/16:/575�/82.

7. Maintz D, Seifarth H, Raupach R, Flohr T, Rink M, Sommer

T, et al. 64-slice multidetector coronary CT angiography:

In vitro evaluation of 68 different stents. Eur Radiol. 2005;/7:/

1�/9.

8. Sato T, Anno H, Kondo T, Harigaya H, Inoue K, Kakizawa S,

et al. Applicability of ECG-gated multislice helical ct to

patients with atrial fibrillation. Circ J. 2005;/69:/1068�/73.

9. Rødevand O, Høgalmen G, Gudim LP, Indrebø T, Mølstad P,

Vandvik PO. Limited usefulness of non-invasive coronary

angiography with 16-detector multislice computer tomo-

graphy at a community hospital. Scand Cardiovasc J. 2006;

(in press).

10. Bartnes K, Sildnes T, Iqbal A, Dahl-Eriksen Ø, Trovik T,

Steigen TK, et al. Coronary bypass graft patency cannot be

determined by multidetector spiral computed tomography.

Scand Cardiovasc J. 2006; (in press).

70 N. Kløw

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