Pathophysiological factors contributing to fractional flow reserve and instantaneous wave-free ratio discordance

The diagnostic accuracy and clinical benefits of instantaneous wave-free ratio (iFR) compared to fractional flow reserve (FFR) have been well-established in the literature. Despite the advantages of non-hyperemic pressure indices, approximately 20% of iFR and FFR measurements are discordant. Efforts have been made to establish the mechanisms as well as identify causative factors that lead to such a discordance. Recent studies have identified many factors of discordance including sex differences, age differences, bradycardia, coronary artery stenosis location, elevated left ventricular end-diastolic pressure, and diastolic dysfunction. Additionally, discordance secondary to coronary artery microcirculation dysfunction, as seen in diabetics and patients on hemodialysis, has sparked interest amongst experts. As more interventional cardiologists are utilizing iFR independent of FFR to guide percutaneous coronary intervention an emphasis has been placed on identifying factors leading to discordance. The aim of this review is to outline recent studies that have identified factors of FFR and iFR discordance.

Automated summary

The diagnostic accuracy and clinical benefits of instantaneous wave-free ratio (iFR) compared to fractional flow reserve (FFR) have been well-established. However, approximately 20% of measurements using iFR and FFR are found to be discordant. Recent studies have identified factors such as sex differences, age differences, bradycardia, and coronary artery stenosis location that contribute to this discordance. Additionally, dysfunction in the coronary artery microcirculation, particularly in diabetics and patients on hemodialysis, has been found to be a significant factor of discordance.