Computed Tomography to Replace Invasive Coronary Angiography?

o diagnose obstructive coronary artery disease (CAD) and consequently determine appropriate treatment is not a trivial task. Invasive coronary angiography (ICA) is considered the reference standard, particularly when combined with hemodynamic interrogation by fractional flow reserve (FFR) in the presence of an intermediate coronary lesion (ie, 30%-90% diameter stenosis). This effective invasive procedure, however, carries inherent risks of potential serious complications and is accompanied by considerable costs, relatively high radiation exposure, and patient discomfort. During the last decade, noninvasive computed tomographic coronary angiography (CCTA) has emerged as a viable alternative to its invasive counterpart. Moreover, as the yield of ICA to detect CAD is low, CCTA has become a gatekeeper to the catheterization laboratory as a negative CCTA of sufficient quality virtually rules out obstructive CAD and significantly reduces unnecessary invasive procedures. 1 Nonetheless, CCTA is considered a screening tool for ICA rather than its replacement owing to poorer image quality because of lower spatial and temporal resolution, motion and blooming artifacts, as well as the dependency on a low and stable heart rate for adequate image acquisition. The low specificity and high false-positive rate of CCTA has been the Achilles heel of this technique and justly mandates further diagnostic approaches in case of a positive scan. In an effort to increase the specificity, myocardial perfusion imaging has been suggested after an ambiguous or positive CCTA. 2 This strategy, however, has proven to add little-to-no value over CCTA alone to diagnose CAD and merely increases specificity at the cost of sensitivity without significantly improving total diagnostic accuracy and may thus be considered even unsalutary for clinical decision-making. 3 Shifting away from these hybrid or sequential imaging strategies now focuses new attention toward optimizing CCTA as a solitude test to provide similar diagnostic information as ICA and potentially replace it as a diagnostic tool for CAD.