Invasive assessment of coronary flow reserve

Coronary angiography is a well-established invasive method of defining coronary anatomy and forms the basis for most decisions between medical therapy, surgery, and percutaneous revascularization in patients with coronary artery disease. Angiography is limited, however, in that it solely provides anatomic information. Although this may be more than adequate when the angiogram reveals an obvious high-grade stenosis or completely normal vessels, very often the angiogram reveals lesions of unclear significance. Uncertainty may arise from poor image quality resulting from the patient’s body habitus or the presence of overlapping vessel segments, arterial tortuosity, eccentric lesions, or diffuse atherosclerosis disease or when the stenosis is of intermediate severity (40%-70% narrowing). In these common scenarios, adjunctive diagnostic testing is crucial to assist the operator in determining the physiologic significance of these lesions and guiding further therapy.