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

Abstract

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 (Q(q)) was continuously recorded. Angiography-based blood flow (Q(a)) was calculated by using a time-density curve based on the first-pass analysis technique. Flow probe-based CFR (CFR(q)) and angiography-based CFR (CFR(a)) were calculated as the ratio of hyperemic to baseline flow using Q(q) and Q(a), respectively. Relative angiographic FFR (relative FFR(a)) was calculated as the ratio of the normalized Q(a) in LAD to the left circumflex artery (LC(X)) during hyperemia. Flow probe-based FFR (FFR(q)) was measured from the ratio of hyperemic flow with and without disease. CFR(a) showed a strong correlation with the gold standard CFR(q) (CFR(a) = 0.91 CFR(q) + 0.30; r = 0.90; P < 0.0001). Relative FFR(a) correlated linearly with FFR(q) (relative FFR(a) = 0.86 FFR(q) + 0.05; r = 0.90; P < 0.0001). The quantification of CFR and relative FFR(a) 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.

Influence of segmented vessel size due to limited imaging resolution on coronary hyperemic flow prediction from arterial crown volume

“…In contrast, the exponent ␤ in our study decreased from 0.79 to 0.55 for truncation radii ranging from 50 to 1,000 m. A value of 3/4 (0.75) for the exponent was previously suggested based on the measured relationship between flow and segment length and the derived relationship between segment length and cumulative arterial volume (31). This value was validated by angiographic imaging at the limited resolution of 500 m (7,15,30). Using theoretical derivation based on rules for branching at bifurcations, a value of 7/9 (0.78) has been suggested (4), which agrees well with ␤ ϭ 0.79 found at our smallest truncation radius (50 m).…”

State of the art paper Comprehensive assessment of coronary fractional flow reserve

“…It was found that pressure-wire measurements of FFR correlated linearly with FFR V according to the equation: FFR = 0.41 FFR V + 0.52 ( p < 0.001) and the correlation coefficient and standard error of estimate were 0.85 and 0.07, respectively [ 75 ]. Thence, this angiographic technique was deemed a potential assessment of the physiological severity of a coronary stenosis during routine diagnostic cardiac catheterization without a need to cross a stenosis with a pressure wire [ 75 , 76 ].…”

Letter to the editor: “A novel angiographic fractional flow reserve”

“…Also, an external vascular occluder was used to produce a moderate epicardial stenosis. Therefore, the angiographic FFR technique was validated not only in the microvascular disruption model but also in the epicardial stenosis model (14). However, continued injections of microspheres may cause heterogeneous microinfarcts, which are not the same pathological change as normal myocardial infarction or diffused microvascular disease.…”