Introduction: Functional testing by stress myocardial perfusion imaging (MPI) and anatomical imaging by coronary computed tomography angiography (CCTA) are often used interchangeably in the initial evaluation of patients suspected to have coronary artery disease (CAD) potentially leading to heart attacks. In patients with an intermediate likelihood of having CAD, the results of functional testing with MPI provide important diagnostic and prognostic information. This information is usually sufficient to determine the need for invasive coronary angiography and coronary artery revascularization. Coronary CTA provides accurate anatomical information regarding the extent and severity of CAD, but often needs objective demonstration of blood flow impairment by further testing before management decisions can be made. Data from randomized controlled trials comparing stress MPI and CCTA as initial tests in patients with intermediate likelihood of CAD have only recently become available, and current practice guidelines do not strongly prefer one modality of testing over the other.
Methods: This international, multi-centric, randomized controlled trial was designed to evaluate the effect of initial testing with stress MPI or CCTA on the use of further downstream testing in patients with suspected CAD. We also compared the costs of the two strategies and the effective radiation dose to patients. One hundred and fifty-one patients were randomized to the MPI arm and 152 to the CCTA arm, and 95% underwent testing as allocated (289/303). All data were entered at participating sites into editable PDF forms with built-in quality checks. The forms were transmitted electronically to the data management centre at the Indian Institute of Public Health-Delhi, where the data were exported into statistical analysis software using a customized form management system. Forty-one of 143 (29%) patients had an abnormal stress MPI and one patient had an inconclusive result. Of those with abnormal MPI results, 14 (10%) had reversible perfusion defects involving >10% of the left ventricle myocardium, while those remaining had less severe defects. An abnormal initial CCTA was reported in 79/141 (56%) patients. Of these, 25 (18%) had at least one lesion with ≥70% diameter stenosis, and 21 (18%) had intermediate lesions (50%-69% diameter stenosis). The median calcium score was 6.7 units with 75% of the patients having a score <97.
Results: This study showed that in the initial evaluation of patients with suspected CAD, a strategy of functional testing with stress-rest MPI compared to CCTA, may result in less downstream testing and less costs, but with a small increase in radiation exposure for patients. These results must be taken into consideration when choosing the initial test for the evaluation of patients with suspected CAD.
Researchers from Brazil, the Czech Republic, India, Italy, Mexico, Slovenia and Turkey participated in this CRP. The study protocol was approved by the ethics committees at all participating sites and all patients provided written informed consent.
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