Mr Ioannis V Vassiliadis,
Coronary calcium, a surrogate marker for the presence and amount of coronary atherosclerotic plaque, can be detected and quantified by non-contrast CT, but its usefulness remains controversial.
In the first part of the session entitled Coronary calcium scoring is useless, Prof J.Airaksinen (Turku,Fi) as protagonist, argued that CTA is not useful as a screening test in asymptomatic patients based on the assumption that early treatment will improve outcomes. A beneficial contribution of coronary calcium assessment to risk stratification can most likely be expected in individuals who seem to be at intermediate risk for coronary events (1,2-2% annual risk). No prospective trials have investigated the predictive value of non-calcified plaque in large group of individuals. Accordingly, it does not yet represent a clinical application in asymptomatic individuals for the purpose of risk stratification. Prof. L.J.Shaw (Atlanta,US), taking an opposite view on the same issue, made it clear that coronary calcium makes it possible to stratify asymptomatic individuals concerning their future cardiovascular risk with a predictive power that is stronger than multiple biomarkers and superior to the traditional cardiovascular risk factors (Framigham risk index). Published data support the hypothesis that high calcium scoring can modify predicted risk obtained from the above risk indexes alone, especially among patients in the intermediate category, in whom clinical decision making is most uncertain (MESA Trial- Heinz Nixdorf Recall Study etc.)
The second part of this session was devoted to coronary computed tomography (CTA) per se, which has emerged as a safe, noninvasive, patient-friendly diagnostic modality to detect the presence of coronary atherosclerosis, questioning if CTA angiography is useless. Prof. W.Wijns (Aalst,BE), presented data supporting the uselessness of CTA. He concluded that MD-CTA does not qualify as a proper screening test by at least 5 out of 7 criteria; that in the presence of non-obstructive plaque (“healthy carriers” of the disease), only about half of the detected plaque is associated with abnormal functional perfusion test; that the incremental prognostic value of MD-CTA above Calcium Scoring is unknown and finally, that there is no prospective trial-based evidence that adding MD-CTA to risk scoring based (ESC HeartScore) has any impact on outcome, while the downsides in terms of risk and cost are all too obvious. Apart from the above, he mentioned that CT angiography has several limitations. It is limited to the anatomic visualization of stenoses and does not provide information as to the functional relevance of a lesion. The precise grading of the severity of a coronary stenosis is hampered in calcified obstructions because of the blooming effect which overestimates the severity of stenosis. Prof. P.J.DeFeyter presented the same issue from an opposite point of view. He stressed that CTA is based on robust technology that is still improving in terms of temporal and spatial resolution, with low contrast and radiation exposure. It proved to be a safe means of detecting high risk asymptomatic subjects while atherosclerotic disease is still in the preclinical stage. Its negative predictive value has uniformly been found to be high, indicating that the technique may be most suitable as a non-invasive tool to rule out the presence of obstructive coronary lesions in a non-selected population with an intermediate pre-test likelihood of disease in several clinical scenarios such as in patients with atypical chest pain, patients with equivocal stress test results, patients with acute chest pain in the absence of ECG changes or enzyme elevations, or patients before non-coronary cardiac surgery.
The issue of the clinical application of CTA and calcium scoring in high risk asymptomatic individuals, despite all the thoughtful and comprehensive presentation above, still remains controversial. It remains for clinical trials to show the incremental value of the findings of CTA in addition to the Framingham or ESC risk scores, and to evaluate the effectiveness and cost-effectiveness of various work-up algorithms in a randomized fashion to see which yield the best outcomes and lowest costs.
Coronary computed tomography to identify high-risk asymptomatic subjects
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