Quantification of absolute coronary flow reserve and relative fractional flow reserve in a swine animal model using angiographic image data

Coronary flow reserve (CFR) and fractional flow reserve (FFR) are important physiological indexes for coronary disease. The purpose of this study was to validate the CFR and FFR measurement techniques using only angiographic image data. Fifteen swine were instrumented with an ultrasound flow probe on the left anterior descending artery (LAD). Microspheres were gradually injected into the LAD to create microvascular disruption. An occluder was used to produce stenosis. Contrast material injections were made into the left coronary artery during image acquisition. Volumetric blood flow from the flow probe (Q̇q) was continuously recorded. Angiography-based blood flow (Q̇a) was calculated by using a time-density curve based on the first-pass analysis technique. Flow probe-based CFR (CFRq) and angiography-based CFR (CFRa) were calculated as the ratio of hyperemic to baseline flow using Q̇q and Q̇a, respectively. Relative angiographic FFR (relative FFRa) was calculated as the ratio of the normalized Q̇a in LAD to the left circumflex artery (LCX) during hyperemia. Flow probe-based FFR (FFRq) was measured from the ratio of hyperemic flow with and without disease. CFRa showed a strong correlation with the gold standard CFRq (CFRa = 0.91 CFRq + 0.30; r = 0.90; P < 0.0001). Relative FFRa correlated linearly with FFRq (relative FFRa = 0.86 FFRq + 0.05; r = 0.90; P < 0.0001). The quantification of CFR and relative FFRa using angiographic image data was validated in a swine model. This angiographic technique can potentially be used for coronary physiological assessment during routine cardiac catheterization.