Objective: The aim of this study was to assess DSCT for evaluation of coronary artery disease in an unselected patient population. Impact of heart rate, heart rate variability and calcification on image quality and diagnostic accuracy were, thereby, considered.
Subjects and Methods: 100 consecutive patients with known or suspected CAD underwent DSCT and invasive coronary angiography. Image quality (IQ) was assessed using a 4-point scale (1: excellent; 4: non-diagnostic). Accuracy of DSCT in detection or exclusion of significant stenosis (>50%) was evaluated on a per-segment and per-patient level. Effects of heart rate, heart rate variability and calcification on IQ and accuracy were analyzed by multivariate regression and between subgroups of predictor variables. Simple regression was performed to calculate thresholds for adequate IQ.
Results: Average heart rate was 64.9± 13.2 bpm, mean variability 23.6± 36.2 beats per CT-examination and mean Agatston score 786.5± 965.9. Diagnostic image quality was obtained in 90.2% of segments. Sensitivity, specificity, positive and negative predictive values for the presence of significant stenosis was: by segment 91.1%, 92.0%, 75.4% and 97.5%; by patient 100%, 81.5%, 93.6% and 100%. According to multivariate regression, IQ was significantly related to heart rate variability and calcification (P=0.025; P<0.0001); number of non-diagnostic segments was significantly affected by calcification only. Also, in a multivariate regression, calcification was the single factor with significant impact on diagnostic accuracy (P=0.0003).
Conclusion: Whilst DSCT achieves heart rate independent image quality, the latter remains prone to heart rate variability and calcification. In an unselected patient collective, calcium burden proves to be the single determinant of diagnostic accuracy.
320-detector row CT coronary angiography: effects of heart rate and heart rate variability on image quality, diagnostic accuracy and radiation exposure
