Impact of Coronary Calcium Score on the Prevalence of Coronary Artery Stenosis on Dual Source CT Coronary Angiography in Caucasian Patients with an Intermediate Risk

Purpose

To investigate the prevalence of significant coronary artery stenosis on coronary computed tomography angiography (cCTA) in symptomatic Caucasian patients with an intermediate risk score at different levels of coronary artery calcification (CAC).

Method

In total, 383 consecutive symptomatic Caucasian patients (147 females, 60 ± 13 years) with an intermediate risk score underwent nonenhanced CT for CAC scoring immediately before contrast-enhanced cCTA on a dual-source CT scanner. Additionally clinically indicated invasive coronary angiography (ICA) was performed in 90 patients. The prevalence of significant coronary artery stenosis (>50%) on cCTA and ICA was correlated at different CAC score levels.

Results

Of 121 patients with a zero CAC score, none had significant coronary artery stenosis on cCTA or ICA. Coronary CTA diagnosed in 54 of 70 patients with high CAC score (>400), a significant stenosis. Subsequent ICA confirmed significant stenosis in 30 of 32 patients. Sensitivity and a negative predictive value of CAC score ruling out significant stenosis on cCTA were 100% and 100%, respectively, using cutoff value of zero and specificity and positive predictive value to predict significant stenosis on cCTA were 79% and 51%, respectively, using a cutoff value of >400.

Conclusion

Significant coronary artery stenosis is extremely unlikely, with an estimated risk of 4 in 1000 patients in symptomatic Caucasian patients with an intermediate risk score and negative CAC score. To reduce radiation exposure, radiation-free tests should be considered for differential diagnosis of chest pain in these patients.

Patients who present at the emergency department complaining of acute chest pain place a substantial economic burden on the health care system. In 2004 alone, more than 6 million of such visits occurred in the United States, with an estimated 30% resulting in hospitalization for suspected acute coronary syndrome (ACS) . However, only a small percentage of those admitted to the hospital for acute chest pain is eventually diagnosed with ACS .

A large body of literature has shown that coronary computed tomography angiography (cCTA) has a high sensitivity to rule out coronary artery stenosis in patients with acute chest pain . Thus, cCTA may be a valuable discriminatory tool for clinical management of these patients. However, a major issue with cCTA is the associated radiation exposure. Recently, several studies have evaluated the radiation exposure associated with cCTA and have reported large variations, with effective doses of up to 30 mSv . Concerns about cCTA radiation exposure have regenerated interest in coronary artery calcium (CAC) measurements because the nonenhanced CT needed for coronary calcium scoring is typically associated with a much lower radiation dose than contrast-enhanced cCTA. The presence of calcium in the coronary arteries is a well-known and pathognomonic marker for atherosclerotic disease . Screening of the asymptomatic population for detection of early-stage coronary artery disease is one of the most promising applications of CAC scoring. Repeat CAC measurements with CT (CAC-CT) can successfully track the progression of atherosclerosis in different clinical settings .

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Materials and methods

Study Population

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Table 1

Patient Characteristics, Findings, and Outcomes

Men 236 (62%) Women 147 (38%) Mean age male 58 ± 13 (range 34–87) Mean age female 62 ± 13 (range 33–85) Nicotine abuse 207 (54%) Hypertension 226 (59%) Diabetes mellitus 91 (24%) Dyslipidemia 115 (30%) BMI 23.7 ± 4.5 (range 17.2–31.5) Family history of cardiovascular disease 88 (23%) Typical angina pectoris 310 (81%) Atypical angina pectoris 73 (17%) Median Agatston score 19.9 (range 0–5602) cCTA diameter stenosis <50% 268 (70%) cCTA diameter stenosis ≥50% 114 (30%) ICA diameter stenosis <70% 60 (52%) ICA diameter stenosis ≥70% 55 (48%) Percutaneous coronary intervention 49 (89%) Bypass surgery 6 (11%)

BMI, body mass index; cCTA, coronary computed tomography angiography; ICA, invasive coronary angiography.

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CT Scanning Protocol

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CT Analysis

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Statistical Analysis

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Results

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Diagnostic Accuracy of Coronary Stenosis for Different CAC Score Cutoff Points

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Table 2

Diagnostic Performance of CAC-CT for the Prediction of Significant Stenosis on cCTA

CAC Score Levels_n_ TP TN FP FN Accuracy % Sensitivity % Specificity % PPV % NPV % >0 383 114 121 148 0 61.4 100 (96–100) 45 (39–51) 43.5 (38–50) 100 (96–100) >10 383 108 178 91 6 74.7 94.7 (88–98) 66.2 (60–72) 54.3 (47–61) 96.7 (93–99) >100 383 93 229 40 21 84.1 81.6 (73–88) 85.1 (80–89) 69.9 (61–77) 91.6 (87–95) >400 383 54 253 16 60 80.2 47.4 (38–57) 94.1 (90–97) 77.1 (65–86) 80.8 (76–85)

CAC, coronary artery calcification; cCTA, coronary computed tomography angiography; FN, false negative; FP, false positive; NPV, negative predictive value; TP, true positive; TN, true negative; PPV, positive predictive value.

Numbers in parentheses represent 95 % confidence interval values.

Table 3

Diagnostic Performance of CAC-CT for the Prediction of Significant Stenosis on cCTA that has been Confirmed by Cardiac Catheterization

CAC Score Levels_n_ TP TN FP FN Accuracy % Sensitivity % Specificity % PPV % NPV % All 90 49 37 3 1 95.6 98 (88–100) 92.5 (79–98) 94.2 (83–99) 97.4 (84–100) 0 10 0 10 0 0 100 - 100 - - 0.1–10 6 1 5 0 0 100 100 (5–100) 100 (46–100) 100 (5–100) 100 (46–100) 10.1–100 15 7 7 1 0 93.3 100 (56–100) 87.5 (47–99) 87.5 (47–99) 100 (56–100) 100.1–400 20 13 7 0 0 100 100 (72–100) 100 (56–100) 100 (72–100) 100 (56–100) >400 39 28 8 2 1 92.3 96.6 (80–100) 80 (44–97) 93.3 (77–99) 88.9 (51–99)

FN, false negative; FP, false positive; NPV, negative predictive value; PPV, positive predictive value; TN, true negative; TP, true positive.

Numbers in parentheses represent 95 % confidence interval values.

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Discussion

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Table 4

Compendium of Studies Involving Coronary Artery Calcium Score by 64-slice Computed Tomography in Patients with a Coronary Artery Calcium Score of Zero

Study (Ref.) Year Patients with 0 CAC Score Obstructive Disease Race Country Manufacturer and System Symptomatic Patients Risk Group Kim et al 2012 1114 48 — Korea Siemens, Somatom Sensation 64 Symptomatic Mixed (14% low, 75% intermediate, and 11% high risk) Ueda et al 2012 260 8 — Japan Siemens, Somatom Sensation 64 Symptomatic (49%) — Yoon et al 2012 92 14 100% Asian Korea Philips, Brilliance 64 Symptomatic Mixed (low, intermediate, and high risk) Alqarqaz et al 2011 333 6 49% white United States GE, Lightspeed Volume Symptomatic Mixed (81% low, 19% intermediate to high risk) Villines et al 2011 5128 179 — Canada, Germany, Italy, Korea, Switzerland, United States — Symptomatic Pretest probability of obstructive CAD: 32% ∗ Uretsky et al 2011 1119 20 — United States GE, Lightspeed Volume Symptomatic — Ergün et al 2010 883 43 — Turkey Toshiba, Aquilion 64 Symptomatic (75%) Mixed (low, intermediate, and high risk) Truong et al 2010 72 14 United States — — — Laudon et al 2010 133 0 — United States GE, Lightspeed Volume Symptomatic Low or intermediate risk Sosnowski et al 2009 166 3 — Poland Toshiba, Aquilion 64 Symptomatic Intermediate risk Akram et al 2009 49 4 — United States Siemens, Somatom Sensation 64 Symptomatic — Sawar et al 2009 183 2 — — — Symptomatic — Kelly et al 2008 325 12 Most patients white United States Siemens, Somatom Sensation 64/GE, LightSpeed VCT Asymptomatic (53%) — Choi et al 2008 825 10 100% Asian Korea Philips, Brilliance 64 Asymptomatic Mixed (55% low, 34% intermediate, and 10% high risk)

—, not stated; GE, general electric; CAC, coronary artery calcium.

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