Multislice Computed Tomography in Acute Coronary Syndromes




High-quality, noninvasive coronary imaging requires high spatial resolution and a high acquisition speed because of the small size, tortuous course, and continuous motion of the coronary arteries. Computed tomography (CT) has emerged as the most effective technique to visualize the coronary arteries noninvasively. Electron beam computed tomography (EBCT), which was introduced in the mid-1980s, is a high-speed CT scanner designed for cardiac imaging. Although mostly used for the detection and quantification of coronary calcium, EBCT also allows contrast-enhanced coronary angiography. Since the early 2000s, multislice computed tomography (MSCT) scanners with cardiac imaging capabilities have been developed. MSCT scanners can be used to detect and quantify coronary calcium, but were primarily developed to image the coronary arteries. Current state-of-the-art scanners are equipped with 64 or more detector rows. Dual-source scanners are available that allow even faster acquisition of images. In this chapter, we will discuss the value of coronary calcium scoring and total coronary plaque burden as assessed by CT, and the role of CT coronary angiography in the evaluation of patients presenting with acute coronary syndromes.


Prediction of Adverse Cardiovascular Events


Computed Tomography Coronary Calcium Scoring


Coronary calcium is easily identified by CT because the roentgenographic attenuation of calcium is much higher compared with that of the surrounding tissues ( Fig. 16-1 ). Histologic studies have shown that a CT tissue density of greater than or equal to 130 HU is highly correlated with calcified coronary plaques. The presence of coronary calcium is evidence of the presence of coronary atherosclerosis. The extent of coronary calcium correlates with the overall atherosclerotic plaque burden (i.e., presence of calcific and noncalcific atherosclerosis), although the calcific plaques constitute only 20% of the total coronary plaque burden. A large amount of coronary calcium is associated with an increased likelihood of vulnerable plaque present somewhere in the coronary tree, but does not identify the site of a specific vulnerable plaque. Absence of coronary calcium does not exclude coronary atherosclerosis, including the presence of a high-risk plaque, but its presence is very unlikely.








FIGURE 16–1


A, a small calcific plaque in LAD; B, extensive calcific plaque in left main LAD and LCx; C, no presence of calcium. High-density calcific plaques visible as bright dots ( arrows ). LAD, left anterior descending artery; LCx, left cireumflex coronary artery.


The amount of coronary calcium can be quantified in different ways. The most widely used method is the Agatston calcium score, based on the peak CT density (>130 HU) and the area of the calcific plaque (≥1 mm 2 ). For each calcified lesion, the area is multiplied by a factor determined by the peak CT density: 1 for a peak density of 130 to 199 HU, 2 for 200 to 299 HU, 3 for 300 to 399 HU, and 4 for 400 HU or more. By adding up the individual plaque scores, the total Agatston score can be determined. Several large-scale long-term follow-up studies have assessed the value of calcium scoring to predict cardiovascular events in high-risk asymptomatic populations ( Table 16-1 ). A coronary calcium score of 0 is associated with a very low risk (<0.4% annual risk) of the occurrence of an adverse cardiovascular event and there is a strong direct relationship between the magnitude of the calcium score and the occurrence of adverse events ( Tables 16-2 and 16-3 ).



TABLE 16–1

Computed Tomography Calcium Score Prediction of Cardiovascular Events


































































































Study (Year) No. of Patients Age (yr) Follow-up (yr) Completeness Follow-Up (%) Predictive Calcium Score Prevalence NP * Comparative Group Calcium Score (Prevalence) End Point (NP) RR
Shaw et al (2003) 10,377 53 ± 0.1 5 100 >40 935 ≤10 (5946) All-cause mortality (249) 6.2
Greenland et al (2004) 1312 66 ± 8 7 88 >300 221 0 (316) Cardiac death/MI (84) 3.9
Arad et al (2005) 4613 59 ± 6 4.3 94 ≥100 1136 <100 (3477) Cardiac death or MI (119) 9.2
Taylor et al (2005) 1627 43 ± 3 3 99 >0 364 0 (1363) Death or MI UA (9) 11.8
Vliegenthart et al (2005) 1795 71 ± 6 3.3 99 >1000 196 0-100 (905) Death/MI (40) 8.1
LaMonte et al (2005) 6835 (men) 54 ± 10 3.5 70 >250 1380 0 (2692) Cardiac death or MI (81) idem 8.7
3911 (women) >113 376 0 (2780) 6.3
Budoff et al (2007) 25,253 56 ± 11 6.8 100 >10 14,207 0 (11,046) All-cause mortality 1.7

RR, relative risk; UA, unstable angina.

* Number of patients with predictive calcium score.


Number of patients in this group with defined calcium score as comparison.


Calculated per 1000 person-years.



TABLE 16–2

Prognostic Value of Coronary Calcium Score for All-Cause Mortality *








































Calcium Score No. of Patients (%) All-Cause Death (%) RRR RRR (Adjusted Risk Factors) *
≤10 5946 (57) 1.0 (62)
11-100 2044 (20) 2.6 (53) 2.5 1.7
101-400 1432 (14) 3.8 (54) 3.6 1.8
401-1000 623 (6.0) 6.3 (39) 6.2 2.6
>1000 332 (3.2) 12.3 (41) 12.3 4.0

RRR, relative risk ratio.

Data from Shaw LJ, Raggi P, Schisterman E et al: Prognostic value of cardiac risk factors and coronary artery calcium screening for all-cause mortality. Radiology 2003;228:826-833.

* 10,377 asymptomatic individuals; total deaths = 2.4% ( N = 249).



TABLE 16–3

Coronary Calcification Predictive of Long-Term Prognosis *







































Calcium Score No. of Patients (%) RRR RRR
(Adjusted Age + Risk Factors)
0 11,046 (44)
1-10 3567 (14) 2.6 1.5
11-100 5033 (20) 6.7 3.6
101-400 3177 (13) 13 3.9
401-1000 1469 (6) 23 6.2
> 1000 965 (4) 38 9.4

RRR, relative risk ratio.

Data from Budoff MJ, Shaw LJ, Liu ST, et al: Long-term prognosis associated with coronary calcification: Observations from a registry of 25,253 patients. J Am Coll Cardiol 2007;49:1860-1870.

* 25,253 asymptomatic individuals; all-cause death, 2% ( N = 510).



A meta-analysis of the prognostic value of coronary calcium was recently performed ( Tables 16-4 and 16-5 ). Overall, the relative risk ratio of having calcium compared with the absence of calcium was 4.3 (95% confidence interval [CI], 3.5 to 5.2) and the relative risk ratios revealed a close relationship with higher calcium scores associated with higher event rates and higher relative risk ratios.



TABLE 16–4

Results of Meta-Analyses of Prognostic Value of Coronary Calcium Score




























Parameter Results
Total no. of patients 27,622
Follow-up (yr) 3-5
CHD death or MI 395
High- vs. low-risk events
364/19,039 events CS > 0
49/11,815 events CS = 0
Relative risk ratio 4.3 (95% CI, 3.5-5.2)

CHD, coronary heart disease; CS, calculated score.

Data from Greenland P, Bonow RO, Brundage BH, et al; Society of Atherosclerosis Imaging and Prevention; Society of Cardiovascular Computed Tomography: ACCF/AHA 2007 clinical expert consensus document on coronary artery calcium scoring by computed tomography in global cardiovascular risk assessment and in evaluation of patients with chest pain: A report of the American College of Cardiology Foundation Clinical Expert Consensus Task Force (ACCF/AHA Writing Committee to Update the 2000 Expert Consensus Document on Electron Beam Computed Tomography) developed in collaboration with the Society of Atherosclerosis Imaging and Prevention and the Society of Cardiovascular Computed Tomography. J Am Coll Cardiol 2007;49:378-402.

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Jan 22, 2019 | Posted by in CARDIOLOGY | Comments Off on Multislice Computed Tomography in Acute Coronary Syndromes

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