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Clinical use of Myocardial SPECT Imaging and CT Angiography in Coronary Artery Disease
Closed for proposals
Project Type
Project Code
E13038CRP
1772Approved Date
Status
Start Date
Expected End Date
Completed Date
12 October 2016Description
The diagnostic and prognostic value of Myocardial Perfusion Imaging (MPI) in Coronary Artery Disease (CAD) is very well established. Nuclear techniques not only provide perfusion and functional data which aid the management decision, it also provides non-perfusion data (e.g. lung to heart ratio -LHR, transient ischemic dilation (TID) of the left ventricle -, right ventricular uptake, myocardial stunning) which can also aid in decision making. Although MPI has many advantages, it has its limitation in that it cannot detect early stage coronary disease, and may miss detection of multi-vessel disease resulting in balanced ischemia. Cardiac Computed Tomography has been vigorously promoted in the detection of coronary disease. The use of coronary calcium score (CCS) for the early detection of atherosclerotic disease has been well established, and it can provide powerful prognostic information, leading to modification in management of CAD, which would not otherwise have been achieved if early disease remained undetected. Presently, cardiac CTA has enough resolution to allow for accurate detection of epicardial coronary stenoses in a majority of cases, although the degree of obstruction is difficult to determine and there is limited correlation with quantitative invasive angiography. The negative predictive value of the technique, however, is very high.To the best of our knowledge, information about the effectiveness of cardiac imaging is not currently available in most low/middle income nations and thus, the proposed study is expected to have a major impact on guidelines and patient management, especially in countries where a significant increase in risk factors for CAD is anticipated over the next decade. The results of this investigation will have a high chance of establishing the limitations for CAD diagnosis by each technique and the possibility to overcome these limitations by the second imaging technique and of establishing the relative merits of each technique for early detection of CAD.
Objectives
The primary objective is to compare the efficacy and costs of an initial strategy of stress-rest MPI to a strategy of initial coronary CTA in the management of asymptomatic or mildly symptomatic patients who are at intermediate risk of coronary events (death or nonfatal MI) by the Framingham criteria.
Specific objectives
Among patients who undergo both tests,
- To correlate calcium score and the degree of stenosis on CTA with the amount of ischemia on MPI.
- To correlate non-perfusion parameters with ischemia and anatomic findings.
- To assess topographic correlation of ischemia and anatomic disease.
To disseminate, transfer and increase awareness of novel imaging technology utilization to developing countries and to standardize protocols for such studies.
To establish the limitations for CAD diagnosis by each technique, the relative merits and the value of each technique for early detection of CAD, for risk stratification and prognosis in CAD.
Impact
Coronary artery disease is highly prevalent throughout the world. It will improve the appropriate use of radiation techniques in assessment of coronary artery disease. Several recent statements have suggested that both stress-rest MPI-SPECT and coronary CTA are appropriate for the initial evaluation of symptomatic patients who have an intermediate likelihood of CAD and are unclear about their respective roles in the initial evaluation of asymptomatic patients at intermediate or high risk of CHD events. this study will clarify the appropriate use. The results of our study are consistent with those from previous observational and randomized studies. In a systematic review, Nielsen and colleagues identified 6 observational studies and one small randomized trial which compared initial functional and anatomical evaluation and reported on downstream test utilization. Combining these results in a meta-analysis, these authors showed that a strategy of initial coronary CTA resulted in greater use of further downstream testing and coronary angiography compared to initial testing with either MPI or exercise ECG (24.4% vs. 18.5%; OR 1.38, 95% CI 1.33-1.43; p=0.0001). The tendency for patients evaluated initially by CCTA to increase the likelihood of downstream coronary angiography (and revascularization) has also been observed in the context of low risk patients with acute chest pain. However, a more recent randomized trial comparing exercise ECG with CCTA in patients with stable chest pain showed a greater use of downstream non-invasive testing in the exercise ECG arm. This was attributable to the large number of inconclusive exercise ECG results (66/245, 27%). The diagnostic performance of exercise ECG is inferior to stress MPI and is perhaps not the modality of choice in a comparative evaluation between anatomical and functional testing
Relevance
This CRP will support MS in the establishment and use of appropriate diagnostic radiation techniques for the evaluation of patients with coronary artery disease which is highly prevalent throughout the world. 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, but with a small increase in radiation exposure to patients. These results must be taken into consideration when choosing the initial test for the evaluation of patients with suspected CAD