Saline-induced Pd/Pa ratio predicts functional significance of coronary stenosis assessed using fractional flow reserve

Aims: Fractional flow reserve (FFR), assessed using distal coronary pressure/aortic pressure (Pd)/(Pa) ratio, functionally evaluates coronary stenosis. An assessment method without vasodilators would be helpful. A single intracoronary bolus of saline decreases Pd because of the speculated low-viscosity effect. We hypothesised that saline-induced Pd/Pa ratio (SPR) could functionally evaluate coronary stenosis. This study aimed to test the accuracy and utility of SPR for predicting FFR <= 0.80. Methods and results: In 137 coronary lesions with over 50% angiographic diameter stenosis, SPR was assessed using an intracoronary bolus of saline (2 mL/s) for five heartbeats (SPR-5) and three heartbeats (SPR-3). FFR was obtained after intravenous adenosine infusion (140 mu g/kg/min). There was a strong correlation between FFR and SPR-5 or SPR-3 (R=0.941 and R=0.933, respectively). Receiver operating characteristic (ROC) curve analysis demonstrated good accuracy (86.3%) for SPR-5, with a cut-off of <0.84 for predicting FFR <0.80 (area under ROC curve 0.96, specificity 94.3, sensitivity 79.9). Thirty-three lesions (24%) were located in the grey zone (SPR 0.83-0.88). No complications were observed in 673 SPR measurements. Conclusions: SPR may accurately predict FFR and can limit adenosine use to one in four lesions. Further studies are needed to confirm the validity of SPR.