QFR Predicts the Incidence of Long-Term Adverse Events in Patients with Suspected CAD: Feasibility and Reproducibility of the Method

Aims: We evaluate feasibility and reproducibility of post hoc quantitative flow ratio (QFR) measurements and their prognostic predictive power during long-term follow-up.

Methods And Results: Between 2010 and 2012, 167 patients without angiographic evidence of significant stenoses were enrolled in a prospective registry. Of these patients, 96% presented 7 years follow-up data. QFR was measured post hoc by three certified investigators. QFR analysis was feasible in 71% of left anterior descending (LAD), 72% of left circumflex (LCX), and 61% of right (RCA) coronaries for a total of 350 measurements repeated in triplicate. Coefficients of variation were 2.1% for RCA and LCX, and 2.8% for the LAD (quartile coefficients of dispersion respectively 1.5, 1.4, and 1.3). QFR ≤0.80 was recorded in 25 patients (27 vessels, in 74% of the cases LAD). A total of 86 major adverse cardiovascular and cerebrovascular events were observed in 76 patients. QFR ≤0.80 in at least one of the three vessels was the strongest predictor of events (HR 3.14, 95%CI 1.78-5.54, p = 0.0001). This association was maintained in several sensitivity analyses.

Conclusions: QFR reproducibility is acceptable, even when analysis is performed post hoc. A pathological QFR is not rare in patients without angiographic evidence of significant stenosis and is a predictor of incident events during long-term follow-up.

Condensed Abstract: In a post hoc analysis of 167 patients without evidence of angiographic significant stenosis, the presence of QFR value ≤0.80 in at least one of the three coronary vessels showed to be the strongest predictor of major adverse cardiovascular and cerebrovascular events during long-term follow-up. QFR reproducibility have been shown to be acceptable among experienced operators.