iFR in Nonculprit Lesions: Measurement Timing May Change History

During primary angioplasty, it is not uncommon to see several other lesions in coronary arteries. Current guidelines advise against the treatment of these lesions in the same primary angioplasty procedure, although there is evidence supporting such a course of action that may warrant changes in these recommendations.

The functional assessment of these nonculprit lesions may help the desicion-making process on the need for revascularization, although it is unclear whether this evaluation might be affected by an acute clinical setting.

Read also: “Patients and Healthcare Providers Benefit from Less Symptoms and Lower Costs with FFR”.

The aim of this study was to answer the question above, i.e., to compare fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) measurements obtained in an acute setting, with FFR and iFR measured at a staged follow-up.

Immediately after successful primary angioplasty of culprit infarction-related vessels, nonculprit stenoses were evaluated with iFR and left without revascularization. Follow-up evaluation with iFR was performed at a later stage; iFR < 0.90 was considered significant.

Read also: “Non-Invasive FFR: CT Evolves from Anatomical to Functional”.

This study included 120 patients with 157 nonculprit lesions. The mean acute iFR for all lesions was 0.89 and the follow-up iFR at an average 15 days after the event was 0.91. Classification agreement was 78% between acute and follow-up iFR.

With follow-up within 5 days after the acute event, almost no difference was observed between acute and follow-up iFR measurements, and classification agreement was about 90%.

Read also: “Routine FFR in Patients with Acute Coronary Syndrome?”

In patients for whom measurements were taken over 15 days apart, follow-up iFR continued increasing and, in consequence, classification agreement was even lower (70%).

Conclusion

Acute iFR measurement in non-culprit infarction-related lesions after successful culprit-vessel primary angioplasty appears valid. However, the time interval from acute to follow-up iFR influences measures, suggesting that inherent physiological factors interfere in acute settings.

Editorial

Most reported information refers to the classification agreement between iFR and FFR, almost always in stable patients. This agreement is (approximately) 80%, considering FFR with a cutoff of 0.80 and iFR with a cutoff of 0.90. In stable patients, the difference between these methods is basically centered around measures close to the cutoffs, which is why confirming iFR measurements between 0.86 and 0.93 by means of FFR (gold standard) seems to be a good practice.

The novelty in this study is the comparison among classification agreements of iFR measured at different times regarding the clinical setting of patients. Some lesions seem to worsen, which could be explained by evolution of the inflammatory process as observed through imaging. In fact, these few lesions also worsened as detected through angiography. However, for most lesions, measures improved over days, thus supporting the idea of stage revascularization of patients undergoing ST-segment elevation myocardial infarction.

Original title: Nonculprit Stenosis Evaluation Using Instantaneous Wave-Free Ratio in Patients with ST-Segment Elevation Myocardial Infarction.

Reference: Troels Thim et al. J Am Coll Cardiol Intv 2017. Article in press.

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