Table 2.

Main strengths and weaknesses of FFR and iFR in LM revascularization decision making.

	Strengths	Weaknesses
FFR	(1) Strong long-term evidence from RCTs and meta-analyses in non-LM lesions (2) Evidence from observational studies and meta-analysis in >500 LM patients	(1) Nonuniform threshold in LM studies (2) Limited evidence for MR if FFR in grey zone (3) Influence of major daughter branch or distal disease (4) Influence of microcirculatory response to a hyperemic stimulus
iFR	(1) Strong medium-term evidence from RCTs in non-LM patients (2) Less influence expected of major daughter branch or distal disease	(1) Limited evidence from 1 observational study in LM patients

LM: left main; FFR: fractional flow reserve; iFR: instantaneous wave-free ratio; RCT: randomized controlled trial; MR: myocardial revascularization.