Borderline Coronary Physiology: Outcomes of Patients with Negative Instantaneous Wave-Free Ratio

Background: Instantaneous wave-free ratio (iFR) is used to guide decision-making in percutaneous coronary intervention (PCI). A ratio of ≤0.89 is reported as indicating haemodynamic significance. Earlier iFR studies have suggested a grey zone of significance of 0.86–0.93. This study reported outcomes of patients with a single interrogated lesion deemed to be non-significant by iFR. Method: A total of 324 lesions were assessed by iFR. Eighty-nine patients had one lesion assessed as non-haemodynamically significant by iFR and left untreated. Adverse outcomes – defined as ongoing angina, myocardial infarction, revascularisation, and death – in this cohort were compared. Results: Forty-seven (53%) lesions were in the left anterior descending (LAD) (mean, 0.93; SD, 0.03); 14 (16%) were in the left circumflex (LCx) (mean, 0.99; SD, 0.03); and 28 (31%) were in the right coronary artery (RCA) (mean, 0.96; SD, 0.03). At follow-up, 17% of the LAD group reported angina, 6% had myocardial infarction (MI), and 2% had undergone further revascularisation; 7% of the RCA group reported angina; none in the LCx group reported events. If 0.93 ‘grey zone’ cut-off was used for LAD lesions, 62.5% of patients with angina at follow-up, and 100% of those with further MI may have been treated with PCI. However, this would come at the cost of 20 patients being treated by PCI who were already destined to be asymptomatic at follow-up. Conclusion: This observational study noted an increased proportion of patients with non-significant LAD lesions reporting ongoing angina at follow-up as compared with LCx or RCA. A large proportion of these may have avoided adverse outcomes if a higher cut-off value was used. More work is required to determine if this trend indicates the need for different cut-off values or ‘grey zones’ for different vessels.