Novel Non-Hyperemic Coronary Physiology Indices for Vessel Longitudinal Analysis

Physiological pattern of coronary artery disease, whether focal or diffuse, is critical in guiding physicians during the decision-making process for percutaneous coronary interventions.

This study introduces two novel non-hyperemic coronary physiology indices designed for longitudinal vessel analysis.

In this prospective observational study, 415 patients underwent pressure-wire functional assessments using instantaneous wave-free ratio (iFR) pullback traces between March 2015 and November 2023 at Verona University Hospital. After applying exclusion criteria, the final study population comprised 198 patients with 209 intermediate coronary lesions. Vessels were qualitatively categorized as focal, diffuse, mixed-focal, or mixed-diffuse based on expert panel interpretation. The novel iFR Pullback Pressure Gradient (iPG) was derived from pullback curves to quantify the atherosclerotic pattern along the vessel. The local severity of lesions was assessed using the instantaneous iFR gradients per unit of length (diFR/ds). Additionally, based on Murray law-based Quantitative Flow Ratio (µFR), both µFR-PPGi and dµFR/ds were computed, to evaluate their correlation with iFR-derived metrics.

The optimal iPG threshold for defining focal disease was 0.71 (Youden index = 0.456), demonstrating good accuracy in predicting the predominant disease pattern (AUC 0.785, p < 0.001). iPG provided an accuracy of 72%, with a sensitivity, specificity, positive predictive value, negative predictive value of 86.5%, 59%, 67.6%, 81.5%, respectively. The µFR-PPGi and dµFR/ds showed significant correlations with iPG and diFR/ds, respectively (r = 0.238, p < 0.001; r = 0.528, p < 0.001).

iPG and diFR/ds are novel quantitative indices for assessing physiological patterns of coronary artery disease, without the need for hyperemia induction. Moderate agreement between angio- and iFR-based indices was found.