iFR/FFR/IVUS Discordance and Clinical Implications: Results From the Prospective Left Main Physiology Registry

Objectives. This study aimed to assess discordance between results of instantaneous wave -free ratio (iFR), fractional flow reserve (FFR), and intravascular ultrasound (IVUS) in intermediate left main coronary (LM) lesions, and its impact on clinical decision making and outcome. Methods. We enrolled 250 patients with a 40%-80% LM stenosis in a prospective, multicenter registry. These patients underwent both iFR and FFR measurements. Of these, 86 underwent IVUS and assessment of the minimal lumen area (MLA), with a 6 mm2 cutoff for significance. Results. Isolated LM disease was recognized in 95 patients (38.0%), while 155 patients (62.0%) had both LM disease and downstream disease. In 53.2% of iFR+ and 56.7% of FFR+ LM lesions, the measurement was positive in only one daughter vessel. iFR/FFR discordance occurred in 25.0% of patients with isolated LM disease and 36.2% of patients with concomitant downstream disease (P=.049). In patients with isolated LM disease, discordance was significantly more common in the left anterior descending artery and younger age was an independent predictor of iFR-/FFR+ discordance. iFR/MLA and FFR/MLA discordance occurred in 37.0% and 29.4%, respectively. Within 1 year of follow-up, major cardiac adverse events (MACE) occurred in 8.5% and 9.7% (P=.763) of patients whose LM lesion was deferred or revascularized, respectively. Discordance was not an independent predictor of MACE. Conclusions. Current methods of estimating LM lesion significance often yield discrepant findings, complicating therapeutic decision -making.