A phantom study of the effect of heart rate, coronary artery displacement and vessel trajectory on coronary artery calcium score: Potential for risk misclassification

BackgroundAccurate coronary artery calcium scoring improves risk stratification in some strata of the population.ObjectiveWe evaluated individual and combined effects of reader experience, heart rate, vessel displacement, and trajectory on computed tomography (CT) Agatston score, calcium volume, and calcium mass in a cardiac phantom model.MethodsA cardiac motion phantom was scanned with a 64-slice CT scanner with artificial electrocardiogram gating with combinations of the following: heart rates 60, 80, and 100 beat/min; vessel displacement of 1.25 and 2.5 cm; and multiple vessel trajectories of craniocaudal, right-left, anteroposterior, right coronary artery (RCA), left anterior descending, and left circumflex (LCX). Calcium quantification was done by 2 different readers with the use of 3 methods: Agatston, calcium volume, and calcium mass.ResultsHeart rate, coronary displacement, and trajectory had significant effects on all 3 techniques, with a general decrease in score as the heart rate increased. A vessel displacement of 2.5 cm decreased the Agatston score by 16% (P < 0.0001) and LCX motion decreased the score by 17% (P < 0.0001). Combined effects often resulted in larger differences; for example, a heart rate of 60 beat/min, vessel displacement of 1.25 cm, and RCA motion resulted in an Agatston score of 907, whereas with a heart rate of 100 beat/min, vessel displacement of 2.5 cm, and LCX motion the score was 604.ConclusionThe calcium score is affected by heart rate, vessel displacement, and trajectory.