Quantitative Flow Ratio vs. Fractional Flow Reserve in STEMI

Quick Takes

  • There remain concerns about reliability and reproducibility of fractional flow reserve (FFR) at the time of STEMI.
  • A post hoc analysis from this study of predominantly men shows that baseline quantitative flow ratio (QFR) is associated with higher overall diagnostic accuracy compared to baseline FFR.
  • The authors conclude that measuring QFR in the subacute STEMI phase may be more reliable than measuring FFR.

Study Questions:

Does quantitative flow ratio (QFR) measured at the time of primary percutaneous coronary intervention (PPCI) reliably predict functional nonculprit lesion (NCL) relevance in the subacute ST-segment elevation myocardial infarction (STEMI) stage?

Methods:

This was a post hoc substudy of the REDUCE-MVI (Reducing Micro Vascular Dysfunction in Revascularized STEMI Patients by Off-target Properties of Ticagrelor) trial. In this trial, which enrolled patients with STEMI and multivessel disease, physiological assessment of NCLs was performed at the time of PPCI and, subsequently, at 30 days. Out of the 110 patients enrolled in the study, 70 patients were also suitable for QFR analysis. All angiograms were analyzed by certified QFR analysts blinded to physiology and clinical data.

Results:

Mean age was 61.8 years and 15.7% of the patients were female. Mean fractional flow reserve (FFR) in NCL was 0.88 (±0.08), significantly higher than mean QFR 0.84 (±0.09) (p = 0.007). Mean FFR at 30-day follow-up was 0.85 (±0.10). Compared to baseline examination, after 30 days, FFR values decreased significantly (0.85 at follow-up vs. 0.88 baseline, p = 0.001), while QFR remained relatively constant (0.83 at follow-up vs. 0.84 baseline, p = 0.310). At baseline evaluation, FFR and QFR showed moderate correlation (Pearson’s r = 0.665, p < 0.001). When compared to 30-day FFR, QFR showed a better correlation (r = 0.906, p < 0.001) than baseline FFR (r = 0.696, p < 0.001). Moreover, Bland-Altman analysis showed superior agreement between QFR and 30-day FFR (mean bias -0.003) as compared to baseline FFR (mean bias -0.026). Using the 0.80 FFR cut-off at 30 days as a reference of hemodynamic relevance, receiver operating characteristic curves showed that the diagnostic accuracy for the detection of FFR <0.80 was superior for QFR as compared to FFR (AUC 0.977 vs. 0.901, p = 0.047). Using standard cut-offs of 0.80 for FFR and QFR, 0 NCL with baseline QFR ≥0.80 showed an FFR <0.80 after 30 days. Based on this, baseline QFR yielded significantly higher specificity, higher negative and positive predictive values, as well as higher overall diagnostic accuracy compared to baseline FFR.

Conclusions:

When performing functional assessment of NCL at the time of PPCI, QFR outperforms FFR in predicting functional NCL relevance at the subacute STEMI stage.

Perspective:

There remain concerns about reliability and reproducibility of FFR at the time of STEMI. Post hoc analysis from this study of predominantly men shows that baseline QFR is associated with higher overall diagnostic accuracy compared to baseline FFR. The authors conclude that measuring QFR in the subacute STEMI phase may be more reliable than measuring FFR. No correlation with clinical events was made in this study and many questions regarding use of either modality to guide management of nonculprit lesions remain.

Clinical Topics: Acute Coronary Syndromes, Invasive Cardiovascular Angiography and Intervention, Stable Ischemic Heart Disease, Vascular Medicine, Interventions and ACS, Interventions and Imaging, Interventions and Vascular Medicine, Angiography, Nuclear Imaging, Chronic Angina

Keywords: Acute Coronary Syndrome, Angiography, Anterior Wall Myocardial Infarction, Fractional Flow Reserve, Myocardial, Hemodynamics, Myocardial Infarction, Percutaneous Coronary Intervention, ST Elevation Myocardial Infarction


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