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KCE Reports 82 Multislice CT in Coronary Heart Disease 35
in some studies to a similar diagnostic accuracy in patients with heart rates above and
below 70/min. 33, 106 Consequently, it has been suggested to omit pre-medication for
heart rate control with dual-source 64-SCT. As will be discussed later, higher heart
rates may allow good quality images to be obtained by using dual-source CT, but this
advantage disappears when radiation limiting protocols are implemented, for which
lower heart rates still remain necessary.
Table 9: Use of pre-test beta-blockers in recent 64-SCT trials in native
coronary arteries.
Study single/dual beta-blocker before CT
Alkadhi dual none; 30,6% were on permanent beta blocker treatment
Hausleiter single if heart rate > 60/min (in 68,7%)
Herzog single if heart rate > 65/min
Leber dual none; 23% were on permanent beta blocker treatment
Ropers dual none; 34% were on permanent beta blocker treatment
Meijboom (gender) single
if heart rate >65/min; in 73% of women
if heart rate >65/min; in 70% of men
Shabestari single if heart rate > 70/min; in 89%
Shapiro single if heart rate > 60/min
Weustink dual none; 71% were on permanant beta-blocker treatment
Single: standard 64-SCT; dual: dual-source 64-SCT. Cfr. Table 7 and text for references.
High calcium load represents the main contributor to stenosis overestimation and falsepositive
ratings with MSCT. In 64-SCT studies, a significant deterioration in specificity in
patients with a high calcium score has been found, which clearly affects PPV. By
including unevaluable segments, in one study PPV decreased from 96% to 60%. 78 In dualsource
MSCT, a similar decrease in specificity on a per-patient analysis was
documented. In patients with an Agatston score of ≤194, specificity was 77.8 while it
was 92.7 in those with a score of ≤194. 33 In a dual-source study by Brodoefel, image
quality was significantly degraded in the presence of Agatston scores >400: whereas test
specificity was 99% in patients with a score ≤100, it was 84% in those with a score
>400. 106 The presence of calcium in the coronary arteries may be a major limitation for
extrapolating the diagnostic performance of MSCT in trials to real-world populations.
The Rotterdam Coronary Calcification Study is a population-based study in which all
inhabitants of a suburb of Rotterdam, aged 55 years or over, were invited to take part.
The median Agatston calcium score (and interquartile range) was 312 (62-970) in men
and 55 (5-261) in women. 107 This finding suggests that in unselected and elderly
populations, the number of non-evaluable patients may be higher than in published trials.
This is illustrated by the high number of inconclusive MSCTs in the outcome trials
discussed earlier, which may be explained by a less strict selection of patients. In one
trial, 67 25% of patients required further testing, owing to intermediate severity lesions
or non-diagnostic MSCTs. In the other, 20 out of 103 patients had suboptimal scans. 80
A deterioration of diagnostic accuracy, has been reported in obese patients. 88 This
restriction is confirmed in dual-source 64-SCT. A comparable decrease in specificity and
positive predictive value was found in both the segment- and patient-based analysis with
higher BMI. While specificity was 89.4% in a patient-based analysis in a subgroup of
patients with a BMI ≤ 26 kg/m², it was 84.1% in those with a BMI >26.0 kg/m². 33 In
addition, the rate of non-evaluable segments was higher in overweight and obese
patients. This deterioration of diagnostic accuracy might be explained by scattering and
absorption of radiation in obese patients resulting in poorer image quality due to an
increase in image noise. 33