Computed tomography in the concurrent assessment of coronary morphology and myocardial perfusion

Rapid advancement in multidetector computed tomography (MDCT) technology has allowed rapid acquisition and assessment of coronary anatomy with high spatial resolution establishing itself as a compelling alternative to invasive coronary angiography (ICA). Coronary MDCT angiography (CTA) is the preferred imaging modality in patients with low- to intermediate-risk probability of coronary artery disease (CAD) given its high sensitivity and negative predictive value in assessment of CAD. However, anatomic imaging does not necessarily implicate that the detected stenosis causes downstream myocardial ischemia, a potential therapeutic target using revascularization procedures. Thus, clinical practice guidelines strongly recommend ischemia assessment prior to elective revascularization procedure. The revascularization in patients with concurrent ischemia has been shown to reduce mortality and symptomatic angina. Initial evidence emerges from the Coronary Artery Surgery Study (CASS) registry which reported that patients with multivessel CAD had improved survival with surgical revascularization in the presence of severe ischemia on exercise stress testing, whereas medical therapy was a better approach in patients without significant ischemia. In the nuclear substudy of the COURAGE trial, coronary interventions resulted in a reduction in myocardial ischemia burden compared to optimal medical therapy arm, and the reduction of ischemia was associated with mitigation in anginal symptoms and translated into improved prognosis of the patients. The FAME (Fractional Flow Reserve vs. Angiography for Guiding PCI in Patients with Multivessel Coronary Artery Disease) trial demonstrated that fractional flow reserve (FFR)-guided intervention to determine the functional severity of a coronary stenosis resulted in about one-third reduction in mortality and rate of coronary events (myocardial infarctions) compared to anatomic evaluation of stenosis alone.