Dual Energy Computed Tomography for Ischemia Determination Compared to "Gold Standard" Non-Invasive and Invasive Techniques

Coronary artery disease is the leading cause of morbidity and mortality in the United States. At present, professional guidelines endorse the use of an array of non-invasive tests for patients with suspected coronary artery disease, which are limited to one of two approaches: 1) physiologic demonstration of ischemia by functional stress testing or 2) anatomic visualization of stenosis by coronary computed tomographic angiography.

Stress test for physiologic assessment of coronary disease is performed most commonly with the prognostic value unsurpassed by other non-invasive tests, with risk of cardiac events escalating exponentially with increasing inducible hypoperfusion. However, despite its high reported performance, the "real world" accuracy of stress test is less sanguine and demonstrates generally poor discrimination of specific vessels that accommodate coronary lesions that cause ischemia. These findings have encouraged the adoption of other stress tests, such as positron emission tomography, which offers reliable attenuation correction, increased count sensitivity, lower radiation dose and enhanced diagnostic performance. Positron emission tomography also enables measures of absolute myocardial blood flow.

Coronary computed tomographic angiography is an alternative test that evaluates coronary disease by direct anatomic visualization of stenoses in a manner similar to cardiac catheterization. Similarly, when employing invasive fractional flow reserve to identify ischemia, high-grade stenoses observed by computed tomography are causal of ischemia less than half of the time.

Multicenter randomized trial data examining invasive methods have demonstrated that a combined anatomic-physiologic approach by catheterization with fractional flow reserve improves identification of patients who may benefit from revascularization, by restricting revascularization to those with high-grade stenoses that specifically cause ischemia. Nevertheless, the combination of catheterization with fractional flow reserve is invasive, is not widely adopted in clinical practice, and is costly.

Computed tomography perfusion is a novel non-invasive technique that can evaluate the physiologic significance of coronary disease, and is performed by adding a single image acquisition to computed tomography in the same setting. The combination of computed tomography perfusion to computed tomography may represent an ideal "one-stop shop" that may allow for both anatomic and physiologic evaluation of coronary disease, serve as a more effective gatekeeper to cardiac catheterization, and better identify patients that would benefit from revascularization.