Effect of Elevated Left Ventricular End Diastolic Pressure on Instantaneous Wave-Free Ratio and Fractional Flow Reserve Discordance

BACKGROUND: Instantaneous wave-free ratio (iFR)-guided physiological assessment has been shown to be non-inferior to fractional flow reserve (FFR)-guided assessment for deciding best treatment strategy for angiographically intermediate stenosis. The diagnostic accuracy of iFR compared to FFR reported in various studies is around 80%. Many factors can lead to iFR/FFR discordance, though underlying physiological mechanism of discordance and its associated factors have not been fully evaluated. The effect of left ventricle end diastolic pressure (LVEDP) on iFR/FFR discordance is unknown and needs further evaluation. METHODS: We performed a single center, non-randomized, both retrospective and prospective study. A total of 65 patients with intermediate coronary stenosis undergoing physiological assessment were included in the study. Patients were assigned to two groups (normal LVEDP and high LVEDP group) based on LVEDP cutoff of 15 mm Hg. iFR and FFR were measured for each patient and iFR/FFR results were compared between the two groups. RESULTS: A significantly large number of patients in elevated LVEDP group had iFR/FFR discordance compared to normal LVEDP group (42.8% vs. 6.7%, P = 0.001). More patients with acute coronary syndrome (ACS) had discordance compared to stale coronary artery disease (CAD) patients (53% vs. 15%, P = 0.003). CONCLUSIONS: Elevated LVEDP can affect iFR and FFR measurements and can lead to discordance. Further studies are required to determine effect of elevated LVEDP on iFR/FFR discordance and whether such discordance is clinically relevant. “Normal range” iFR results should be cautiously interpreted in patients with elevated LVEDP, especially those with ACS.