Effect of electrocardiogram triggering on reproducibility of coronary artery calcium scoring

PURPOSE: To test the hypothesis that computed tomographic (CT) scanning dur ing early rather than middle diastole can significantly reduce the intersca n variability of coronary artery calcium (CAC) scores. MATERIALS AND METHODS: Five hundred thirty-eight patients were initially en rolled; 282 of them were found to have CAC at electron-beam CT and underwen t repeat scanning to measure interscan variability with different electroca rdiogram (ECG) triggers. Eight patients were excluded owing to respiratory motion; thus, 274 asymptomatic patients were examined. Patients were random ly assigned to different ECG trigger interval groups: 40% (group 1), 50% (g roup 2), 60% (group 3), and 80% (group 4). Patients in whom more than one-t hird of sections had greater than 10% ECG trigger variability were classifi ed in the untriggered group (group 5). Interscan variation was compared amo ng all five groups. RESULTS: 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 gro up 1, as compared with the reduced variabilities in group 4 (P < .01 for bo th measures). Breath holding was adequate in 812 cases, and ECG triggering was correct in 790 of cases. CONCLUSION: 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.