Effect of Electrocardiogram Triggering on Reproducibility of Coronary Artery Calcium Scoring

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Abstract
To test the hypothesis that computed tomographic (CT) scanning during early rather than middle diastole can significantly reduce the interscan variability of coronary artery calcium (CAC) scores.Five hundred thirty-eight patients were initially enrolled; 282 of them were found to have CAC at electron-beam CT and underwent repeat scanning to measure interscan variability with different electrocardiogram (ECG) triggers. Eight patients were excluded owing to respiratory motion; thus, 274 asymptomatic patients were examined. Patients were randomly assigned to different ECG trigger interval groups: 40% (group 1), 50% (group 2), 60% (group 3), and 80% (group 4). Patients in whom more than one-third of sections had greater than 10% ECG trigger variability were classified in the untriggered group (group 5). Interscan variation was compared among all five groups.Interscan variabilities in CAC groups 1-5 were 11.5%, 15.3%, 20.3%, 17.4%, and 33.1%, respectively, for total calcium area, and 15.0%, 23.3%, 25.6%, 24.0%, and 42.4%, respectively, for total calcium score. CAC score variability was reduced by 34%; and calcium area variability, by 38% in group 1, as compared with the reduced variabilities in group 4 (P <.01 for both measures). Breath holding was adequate in 812 cases, and ECG triggering was correct in 790 of cases.Study results strongly support the use of an ECG trigger of 40% rather than 80% of the R-R interval in electron-beam CT calcium studies.