A Bidomain numerical validation for assessing times of fast and ending repolarization from monophasic action potentials

3D numerical simulations of unipolar electrograms (EGs) and hybrid monophasic action potentials (HMAPs) were performed by using the cardiac Bidomain model with homogeneous and heterogeneous Luo–Rudy I membrane models. While estimating local recovery times from EGs can be difficult in case of flat T-waves or linear ST ramps, the HMAP signal always displays a monophasic downstroke as does the transmembrane action potential (TAP) and contains valuable information for assessing repolarization time. The simulation results show that: (a) the HMAP fast repolarization time is a reliable estimate of the TAP fast repolarization time; (b) the HMAP ending (90%) repolarization time is a less reliable estimate of the TAP ending repolarization time; (c) analogous conclusions hold for the associated action potential durations APD and APD90.