A method for estimating the physiological significance of each of serial vascular lesions

The physiological severity of a stenosis is determined by its fractional flow reserve (FFR). Coronary arteriosclerosis is a diffuse disease, and it is not uncommon for 2-3 serial lesions to be observed in the same vessel. Direct measurement of the physiological severity of each lesion is impossible due to the hemodynamic interaction between them. The "true FFR" of a given lesion is defined as the FFR that would be measured if other stenoses in the same vessel were absent. Applying the hypothesis that the pressure gradient across a stenosis is proportional to the square of the flow, we obtained equations that are nonsensitive to collateral flow. We applied these equations to the human data of 32 patients with tandem stenoses that were presented by Pijls et al. (2000). The correlation between the true FFR calculated by the suggested method and the FFR measured after treatment of one of the lesions for all 32 patients was significant (R=0.9).