Introduction: Primary percutaneous intervention (PPCI) of non-culprit vessels in ST-segment elevation myocardial infarction (STEMI) patients is associated with improved clinical outcome. Fractional flow reserve (FFR) can guide revascularization of these non-culprit lesions. Recently instantaneous wave free ratio (iFR) was introduced as an adenosine-free alternative to FFR in patients with stable coronary artery disease and non-STEMI. In the acute setting of STEMI, coronary hemodynamics are altered, potentially influencing both FFR and iFR.
Hypothesis: We hypothesize that FFR increases and iFR decreases from the index procedure to follow-up in patients with STEMI.
Methods: We included 43 STEMI patients with an additional non-culprit coronary lesion. Following successful PPCI, resting and hyperaemic intracoronary pressure measurements were performed. These measurements were repeated at 1-month follow-up. FFR and iFR were calculated for both time-points.
Results: FFR significantly decreased (0.89±0.07 versus 0.87±0.08, p=0.003) and iFR significantly increased between baseline and follow-up (0.94±0.07 versus 0.95±0.05, p=0.025). Bland-Altman analysis showed a bias of 0.024 (FFR) and -0.021 (iFR). There was a significant correlation between FFR and iFR at baseline (ρ=0.612) and during follow-up (ρ=0.666)(p<0.001 for both). Discordance between baseline and follow-up was 23.3% in FFR compared to 11.6% in iFR, using established cut-off values (p=0.125).
Conclusions: In patients with STEMI, FFR is slightly higher in the acute setting as compared to follow-up, whereas iFR is slightly lower. This could potentially influence decisions regarding revascularization at the index event as compared to follow-up. Discordance between baseline and follow-up values were found in both FFR and iFR.