Clinical Trial DesignMulticenter Evaluation of Coronary Dual-Source CT Angiography in Patients with Intermediate Risk of Coronary Artery Stenoses (MEDIC): Study design and rationale
Introduction
Multidetector row CT (MDCT) allows visualization of the coronary arteries and detection of coronary artery stenoses. Two meta-analyses of trials performed by 64-slice CT reported sensitivities for detection of coronary artery stenoses in patients referred for a first diagnostic coronary angiogram to range from 73% to 99%, with specificities between 93% and 97%.1, 2 Although numerous single-center trials have evaluated the performance of 64-slice coronary CT angiography (CTA), so far only 3 multicenter trials with cohort sizes from 230 to 360 patients have been published in peer-reviewed journals.3, 4, 5
Dual-source CT (DSCT) allows imaging of the coronary arteries with better temporal resolution compared with 64-slice CT and may therefore be better suited to identify coronary artery stenoses in patients with elevated heart rates. In smaller trials performed without systematic use of β-blockers, sensitivities of 90% to 96% and specificities of 92% to 98% were reported for the detection of coronary artery stenoses on a per-segment level.6, 7, 8, 9, 10 The maximum number of patients included in these trials was 170, and no large trial that assesses the accuracy of DSCT for the detection of coronary artery stenoses has so far been performed.
According to an American Heart Association scientific statement, the use of coronary CTA is most likely considered clinically beneficial in patients who are at intermediate risk for having coronary artery stenoses: Especially in the context of ruling out stenosis in patients with low to intermediate pretest likelihood of disease, CT coronary angiography may develop into a clinically useful tool. CT coronary angiography is reasonable for the assessment of obstructive disease in symptomatic patients (Class IIa, Level of Evidence: B, p. 1763).11 Another recent statement on noninvasive imaging of the coronary artery reads as follows: The potential benefit of noninvasive coronary angiography is likely to be greatest and is reasonable for symptomatic patients who are at intermediate risk for coronary artery disease after initial risk stratification, including patients with equivocal stress-test results (Class IIa, level of evidence B, p. 598). Diagnostic accuracy favors coronary CTA over MRA [magnetic resonance angiography] for these patients (Class I, level of evidence B, p. 598).12
A sufficiently large clinical trial is therefore needed to confirm the diagnostic accuracy of DSCT coronary angiography in a multicenter setting and to confirm the clinical utility of coronary CTA, specifically in patients with intermediate pretest likelihood of coronary artery stenosis.
Section snippets
Overall study design and population
The Multicenter Evaluation of Coronary Dual-Source CT Angiography in Patients with Intermediate Risk of Coronary Artery Stenoses (MEDIC) trial is a prospective, multicenter, international trial to evaluate the diagnostic performance of DSCT for the detection of coronary artery stenoses. The study includes 8 sites in Germany, India, Mexico, the United States, and Denmark (Table 1). All sites participating in the trial are academic medical centers apart from the CARE Hospital in India. Patient
Results
The aim of the MEDIC trial is to identify the accuracy of DSCT to detect coronary artery stenosis (diameter reduction >50% and >70% on a per-segment, per-vessel, and per-patient level) compared with invasive coronary angiography as the reference standard and the influence of relevant factors such as body weight, heart rate, and coronary calcifications on accuracy measures. All outcome measures are listed in Table 6.
Discussion
The use of coronary CTA to detect or exclude coronary artery stenoses in patients with suspected coronary disease has been increasing over the past years and is currently part of the clinical workup in specific patient populations. The diagnostic accuracy of coronary CTA to rule out or detect coronary artery disease has been reported in numerous single center trials that used different CT scanner technologies.1, 2 So far, only 3 trials have assessed the performance of 64-slice CT in a
Conclusion
The results of the MEDIC trial aim to deliver information about the diagnostic accuracy and performance of DSCT for detection of significant coronary stenosis in patients with intermediate pretest likelihood of coronary artery disease. The exclusion and inclusion criteria were designed to identify a clinically relevant patient cohort with suspected coronary artery disease. The multicenter and international nature of the study affords for broad generalization of the study results.
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Conflict of interest: Stephan Achenbach: Research Grants, Siemens/Bayer/Abbott Vascular. Mohamed Marwan: Speaker honoraria for Edwards and Siemens. Suhny Abbara: Royalties: Elsevier, Amirsys, Consulting: Radiology Consulting Group (FDA trial reads), Research Funding: NIH. Jörg Hausleiter: Speaker honoraria for Abbott Vascular and Edwards.