Postprocedural resistance of the target lesion is a strong predictor of subsequent revascularization: assessment by a novel lesion-specific physiological parameter, the epicardial resistance index

Objective evaluation of the functional significance of individual stenosis in patients with multiple lesions is crucial when performing percutaneous coronary intervention (PCI). Here we propose a novel lesion-specific parameter, the epicardial resistance index (ERI), which is derived from intracoronary pressure measurements, and validate its clinical usefulness. The ERI is defined as the ratio of the resistance of an epicardial coronary stenosis to that of downstream myocardium. After obtaining intracoronary pressure data by pull-back of a 0.014″ pressure wire, the ERI was calculated as the trans-lesional pressure gradient divided by (Pd–Pv) at maximum hyperemia, where Pd = the mean distal coronary pressure in the absence of any stenosis and Pv = the central venous pressure. Using 170 measurements obtained from 75 patients, the correlation of ERI with parameters obtained from quantitative coronary angiography (QCA) and intravascular ultrasound (IVUS) was studied. ERI showed a significant correlation with the QCA-derived percent diameter stenosis (r = 0.67, P < 0.001), and with the IVUS-derived minimum luminal area (r = 0.68, P < 0.001). In 55 patients who underwent PCI with bare metal stents, a postprocedural target lesion ERI value greater than 0.16 strongly predicted the need for subsequent revascularization within six months (81% sensitivity and 80% specificity). The ERI is a useful pressure-derived hemodynamic parameter that correlates with anatomical parameters. In addition, the postprocedural resistance of the target lesion indicated by the ERI is a reliable predictor of the late outcome of PCI.