The aim of this study was to determine the prognostic value of fractional flow reserve (FFR) of non-culprit lesions in STEMI patients. 

We analyzed data of all Compare-Acute patients (Comparison Between FFR Guided Revascularization Versus Conventional Strategy in Acute STEMI Patients With MVD) after PCI, from lesions assessed with FFR and treated medically.  The treating cardiologists were blind to FFR values. 

Primary end point was a The primary endpoint was the composite of cardiovascular mortality, target vessel-related (non-IRA with FFR measurement at primary percutaneous coronary intervention) nonfatal MI, and target vessel revascularization: major adverse cardiac events at 24 months. 

It included 751 patients (963 vessels). Non-culprit lesions that were not revascularized showed significantly lower FFR (0.78 vs. 0.84; p<0.001). 

This difference was significative in all vessels.

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Mean FFR of original non- culprit lesions that later presented as MI also resulted lower (0.79 vs. 0.84; p=0.016).

All data point to a significantly higher events rate (p<0.001) in the lowest tertile of FFR (<0.80) compared against the two higher tertiles (0.80 to 0.87 and >0.88).

This phenomenon has been seen in previous studies. We should get rid of this idea of FFR provides a binary cutoff value around 0.8 and rather understand these results as a continuum of variables.  

Read also: COMPARE-ACUTE: FFR-Guided Non-Culprit Vessel Revascularization in Primary Angioplasty.

In any given lesion, the closer to 0.8, the higher the chances of these lesions evolving with events. This increase in bad odds is not linear, but rather shoots up disproportionally the closer we get to 0.8.

Conclusion

In patients with ST elevation MI and multivessel disease undergoing medical treatment in non-culprit lesions after successful primary PCI, there is a non-linear and inverse correlation between FFR values in non-culprit lesions and events. 

It is important to highlight there is worse prognosis around the 0.8 cutoff value.

Original Title: The Natural History of Nonculprit Lesions in STEMI. An FFR Substudy of the Compare-Acute Trial.

Reference: Zsolt Piróth et al. J Am Coll Cardiol Intv 2020;13:954–61.

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