Validation of angiography-based FFR in non-culprit vessels of patients presenting with STEMI

Fractional flow reserve (FFR) for non-culprit lesions (NCLs) in patients with ST-elevation myocardial infarction (STEMI) can be influenced by temporary changes in microvascular resistance. Angiography-derived vessel fractional flow reserve (vFFR) has been tested as a less-invasive alternative.

The FAST STEMI II study aimed to assess the diagnostic performance of acute-setting vFFR vs. FFR for intermediate NCLs in STEMI patients.

FAST STEMI II is a prospective two-center cohort study including STEMI patients with ≥ 1 intermediate NCL (50-90% diameter stenosis). Patients with cardiogenic shock, prior revascularization of the non-culprit vessel, or aorta-ostial lesions were excluded. Following primary percutaneous coronary intervention (PCI), vFFR, FFR, resting full-cycle ratio (RFR), coronary flow reserve (CFR), and index of microcirculatory resistance (IMR) measurements of the NCL were performed.

A total of 111 patients were included. Median [25th-75th percentile] vFFR and FFR were 0.83 [0.74-0.88] and 0.83 [0.80-0.90], respectively. vFFR had a moderate to good discriminative ability to predict FFR ≤ 0.80 (AUC: 0.78; 95% CI: 0.68-0.89; p < 0.001) with a moderate correlation (r = 0.54; p < 0.001). Diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of vFFR to predict FFR ≤ 0.80 were 72%, 76%, 70%, 53%, and 87%, respectively. Microvascular dysfunction (CFR < 2.0 and IMR ≥ 25) was observed in 33 (31%) patients. In patients with microvascular dysfunction, median vFFR and FFR values were 0.76 [0.71-0.86] and 0.85 [0.77-0.90], respectively (p = 0.002).

We found moderate correlation between vFFR and FFR in NCLs of patients undergoing primary PCI. Discordance between vFFR and FFR was associated with the presence of microvascular dysfunction. The study was conducted in accordance with Good Clinical Practice and the Declaration of Helsinki and was registered at 22-jun-2023 on clinicaltrials.gov under the identifier NCT05698719.