Assessment of fractional flow reserve and instantaneous wave-free ratio dynamics in patients with st-segment elevation myocardial infarction and its dependence on the presence of microvascular obstruction in the infarct zone

Objective. To analyze the dynamics of coronary physiology indices — fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) — in the infarct-related artery (IRA) and non-infarct-related artery (non-IRA) during the first 24 hours of ST-segment elevation myocardial infarction (STEMI) and in the early postinfarction period, and to assess their dependence on the presence of microvascular obstruction (MVO) in the infarct zone as determined by contrast-enhanced cardiac magnetic resonance imaging (MRI). Materials and methods. FFR and iFR were measured in the IRA and non-IRA after primary percutaneous coronary intervention (pPCI) on the IRA in patients with STEMI and at least one 50–85% stenosis in a non-IRA. Papaverine was used to induce hyperemia for FFR assessment. Cardiac MRI was performed on days 3–5 to evaluate the presence and extent of MVO in the infarct zone. Repeated coronary angiography with FFR and iFR measurement was performed at 30–45 days; based on the results, non-IRA stenting was performed when FFR ≤ 0.80 and/or iFR ≤ 0.89. To achieve the study objective, the dynamics of coronary physiology indices in the IRA and non-IRA were assessed in the overall cohort and in subgroups with and without MVO on MRI. Statistical analysis included the Wilcoxon signed-rank test, the Mann–Whitney U test, and Spearman's correlation. Results. Thirty-two patients were enrolled. MVO was detected in 13 patients (40.6%). No statistically significant changes in FFR or iFR between the index procedure and repeated assessment were found in either the IRA or the non-IRA (p=0.856 and 0.597 for FFR, p=0.092 and 0.511 for iFR, in the IRA and non-IRA, respectively). The presence of MVO with an extent of 2.47% [0.66%; 5.06%] was not associated with significant differences in FFR or iFR dynamics (p=0.488 (FFR), p=0.089 (iFR) in the IRA; p=0.460 (FFR) and 0.144 (iFR) in the non-IRA). MVO extent of 2.47% [0.66%; 5.06%] did not correlate with changes in FFR or iFR in either the IRA or the non-IRA (the most pronounced trend was observed for ΔiFR in the IRA: ρ=−0.529, p=0.063). Categorical classification stability was 92.0% for FFR and 86.0% for iFR. Conclusion. In hemodynamically stable patients with STEMI and intermediate nonIRA stenoses, FFR and iFR values in both the non-IRA and the IRA after pPCI remain stable during the first 24 hours of MI and in the early postinfarction period. Coronary physiology indices (FFR, iFR) can be used for decision-making regarding non-IRA PCI during the index procedure. In patients with STEMI with a median ejection fraction of 52.5% [49.75%; 58.25%] and MVO extent of 2.47% [0.66%; 5.06%], the presence of MVO did not distort the reproducibility of FFR and iFR measurements in the non-IRA and IRA after pPCI.