The safety of physiology-based coronary revascularisation has been supported by evidence for years now. DEFER (1998-2001) was one of the first related studies. However, major changes in device and medical treatment safety and efficacy have taken place since then. This could affect clinical results, particularly as regards acute coronary syndromes (ACS). Several studies have cast doubts as to the safety of deferring lesions using fractional flow reserve (FFR). Transient microcirculatory dysfunction in both culprit and non-culprit vessels, and reduced hyperaemic responses have been proposed as mechanisms that could change outcomes for ACS patients.

Patients were randomized (1:1) to undergo FFR or instantaneous free-wave ratio (iFR) in each clinical presentation (chronic stable angina or ACS).

This study included 4529 patients, 2130 of which received deferred treatment based on FFR or iFR results. Among these, there were 1675 patients with chronic stable angina (CSA) (iFR: 885; FFR: 790) and 440 with ACS (iFR: 222; FFR: 218).

Upon global assessment of all patients, the primary endpoint turned out to be similar (iFR, 6.47% vs. FFR, 6.41%; hazard ratio [HR]: 1.03; 95% confidence interval [CI]: 0.81, 1.31; p = 0.81). The same happened upon assessment of patients for which revascularization was deferred based on the functional study (iFR, 4.12%, vs. FFR, 4.05%; HR: 1.05; 95% CI: 0.69, 1.60; p = 0.82).

In the analysis according to clinical presentation, patients admitted with ACS had worse outcomes than those with CSA (5.9% vs. 3.6%; HR: 0.62; 95% CI: 1.53 to 0.99; p = 0.04). Such a difference could be explained by failure in the assessment of acute patients through FFR (FFR: ACS, 6.4%, vs. CSA, 3.4%; HR: 0.52; 95% CI: 0.27 to 1.00; p < 0.05). iFR, which does not require hyperemia, showed no significant differences upon assessment of both patient groups (ACS, 5.4%, vs. CSA, 3.8%; HR: 0.74; 95% CI: 0.38 to 1.43; p = 0.37).

Patients who underwent revascularization and did not present deferring lesions had similar outcomes (ACS, 8.7%, vs. CSA, 8.5%; HR: 0.91; 95% CI: 0.67 to 1.24; p = 0.55).

Conclusion

iFR guided functional revascularization in this patient cohort more frequently. Adverse events were few and similar throughout the year, but patients with acute coronary syndrome as assessed by FFR (presenting deferred lesions) experienced more events than those who underwent iFR.

Dr. Javier Escaned

Original title: Safety of Coronary Revascularization Deferral Based on iFR and FFR Measurements in Stable Angina and Acute Coronary Syndromes: A Pooled Patient-Level Analysis of DEFINE FLAIR and IFR SWEDEHEART.

Presenter: Javier Escaned.

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