Functional Approach for Coronary Artery Disease: Filling the Gap Between Evidence and Practice

The presence of myocardial ischemia is the most important prognostic factor in patients with coronary artery disease, and ischemia-directed revascularization has been a standard of care. Fractional flow reserve (FFR) is an invasive method used to detect the functionally significant epicardial coronary stenosis, and FFR-guided revascularization strategy has been proven to be superior to angiography-guided strategy. Recently, a hyperemia-free index, instantaneous wave free ratio (iFR), was developed and showed its non-inferiority for clinical outcomes compared with FFR-guided strategy. While evidence supporting the benefit of pressure wire assessment exists, there remain several unresolved issues, such as the mechanism of discordance between resting and hyperemic physiologic indices, clinical outcomes of patient/lesions with discordant results among the physiologic indices, role of physiologic indices beyond per-vessel decision tool, and the role of microvascular dysfunction in patient prognosis. The current article will review the recent studies performed to address these questions.

Physiologic approach for coronary intervention

When invasively assessing coronary artery disease, the primary goal should be to determine whether the disease is causing a patient's symptoms and whether it is likely to cause future cardiac events. The presence of myocardial ischemia is our best gauge of whether a lesion is responsible for symptoms and likely to result in a future cardiac event. In the catheterization laboratory, fractional flow reserve (FFR) measured with a coronary pressure wire is the reference standard for identifying ischemia-producing lesions. Its spatial resolution is unsurpassed with it not only being vessel-specific, but also lesion-specific. There is now a wealth of data supporting the accuracy of measuring FFR to identify ischemia-producing lesions. FFR-guided percutaneous coronary intervention of these lesions results in improved outcomes and saves resources. Non-hemodynamically significant lesions can be safely managed medically with a low rate of subsequent cardiac events.