Virtual Fractional Flow Reserve (vFFR) is an emerging technology that assesses the severity of coronary stenosis by means of patient specific of Computational Fluid Dynamics simulations. To be of practical clinical utility within a catheter laboratory, FFR results must be obtainable within minutes to guide intervention. We present the design of a novel Lattice-Boltzmann method code specifically tailored for fully automatic near real-time 3D coronary blood flow simulations. The key contributions of the work include a hybrid multicore-GPU accelerated sparse lattice generation algorithm and specialized 3D-0D coupled hemodynamics solver. We present results on state of the art GPU hardware, simulating hemodynamics within multi segment coronary tree. The results demonstrate that vFFR simulations can be performed in the order of minutes, making the replacement of pressure wire based FFR in a catheter laboratory setting with vFFR simulations feasible, without the need to reduce the fidelity of the hemodynamics modelling.