I t may seem intuitively obvious to even the most casual observer that the tighter a coronary stenosis is the more ischemia is produced, and the more likely it is that stenosis will lead to a future adverse cardiac event. The natural history of atherosclerotic lesions is related to both structure (luminal anatomic and plaque morphologic features) and function (i.e., the pathophysiology) of the diseased atherosclerotic vessel (1). Longitudinal studies of patients using nuclear stress testing have clearly linked global ischemia with worse outcomes and a larger benefit from revascularization. Conversely, minimal ischemia carries a favorable, reassuring prognosis (2). In contrast to nuclear stress testing, the link between angiographic stenosis severity and outcomes is more tenuous, due to interobserver variability and the limits of the 2-dimensional coronary angiogram in representing the 3-dimensional structure of a coronary stenosis and its impact on coronary blood flow. The weak relationship between ischemic test results (and outcomes) with the angiographic image, also known as a visual (anatomic)-functional (physiologic) mismatch, confounds the clinician and can lead to inappropriate treatment.