Lesion flow coefficient: a combined anatomical and functional parameter for detection of coronary artery disease--a clinical study.

Invasive diagnosis of coronary artery disease utilizes either anatomical or functional measurements. In this study, we tested a futuristic parameter, lesion flow coefficient (LFC, defined as the ratio of percent coronary area stenosis (%AS) to the square root of the ratio of the pressure drop across the stenosis to the dynamic pressure in the throat region), that combines both the anatomical (%AS) and functional measurements (pressure and flow) for application in a clinical setting. In 51 vessels, simultaneous pressure and flow readings were obtained using a 0.014" Combowire (Volcano Corporation). Anatomical details were assessed using quantitative coronary angiography (QCA). Fractional flow reserve (FFR), coronary flow reserve (CFR), hyperemic stenosis resistance index (HSR), and hyperemic microvascular index (HMR) were obtained at baseline and adenosine-induced hyperemia. QCA data were corrected for the presence of guidewire and then the LFC values were calculated. LFC was correlated with FFR, CFR, HSR, and HMR, individually and in combination with %AS, under both baseline and hyperemic conditions. Further, in 5 vessels, LFC group mean values were compared between pre-PCI and post-PCI groups. P<.05 was considered statistically significant. LFC measured at hyperemia correlated significantly when the pressure-based FFR, flow-based CFR, and anatomically measured %AS were combined (r = 0.64; P<.05). Similarly, LFC correlated significantly when HSR, HMR, and %AS were combined (r = 0.72; P<.05). LFC was able to significantly distinguish between pre-PCI and post-PCI groups (0.42 ± 0.05 and 0.05 ± 0.004, respectively; P<.05). Similar results were obtained for the LFC at baseline conditions. LFC, a futuristic parameter that combines both the anatomical and functional endpoints, has potential for application in a clinical setting for stenosis evaluation, under both hyperemic and baseline conditions.