Agreement between nonculprit stenosis follow-up iFR and FFR after STEMI (iSTEMI substudy)

Area of Science:

• Cardiology
• Interventional Cardiology
• Physiology

Background:

• ST-segment elevation myocardial infarction (STEMI) requires prompt management of culprit lesions.
• Nonculprit coronary stenoses may require functional assessment, but their evaluation after STEMI is less defined.
• Instantaneous wave-free ratio (iFR) and fractional flow reserve (FFR) are physiological indices used to assess stenosis severity.

Purpose of the Study:

• To evaluate the agreement between iFR and FFR for functional assessment of nonculprit coronary stenoses.
• To determine if the time interval after STEMI influences the agreement between iFR and FFR.

Main Methods:

• iFR and FFR were measured in 112 STEMI patients with 146 nonculprit stenoses at staged follow-up.
• Patients were analyzed based on the time interval between STEMI and follow-up assessment (<5 days vs. ≥5 days).
• Agreement rates and discrepancies between iFR and FFR classifications were compared between the two time groups.

Main Results:

• Overall agreement between iFR and FFR was 77% within 5 days and 86% after 5 days post-STEMI (p=0.19).
• Disagreements showed a higher proportion of hemodynamically significant iFR with non-significant FFR in the early (<5 days) group (63%) compared to the later (≥5 days) group (20%) (p=0.04).
• Classification agreement was comparable to that observed in stable patients.

Conclusions:

• The time interval between STEMI and follow-up evaluation impacts the agreement between iFR and FFR for nonculprit stenoses.
• Functional assessment of nonculprit lesions using iFR and FFR may require consideration of the timing relative to the index STEMI event.
• Agreement between iFR and FFR improves beyond 5 days post-STEMI.