Performance evaluation of cardiac repolarization markers derived from unipolar electrograms and monophasic action potentials: A simulation study

Objectives. The aim of this work is to provide a quantitative analysis of cardiac repolarization time (RT) markers derived from unipolar electrograms (EGs) and hybrid monophasic action potentials (HMAPs) under normal and ischemic conditions. These markers are compared with the gold standard RT markers based on the transmembrane action potential (TAP). Methods. The analysis is based on large scale parallel 3D numerical simulations of the action potential propagation modeled by the anisotropic Bidomain system coupled with the Luo-Rudy I membrane model. Activation and recovery sequences elicited by local stimulus are simulated in an insulated block of cardiac tissue with rotational fiber anisotropy, homogeneous intrinsic cellular properties and in presence of an ischemic region. Results. We found a very high correlation (> 0.98) between any of the EG- or HMAP-based markers and the associated TAP-based markers, for tissues with both homogeneous cellular properties and in presence of an ischemic region. Despite this good global match, our results also show that the EG-based markers may be locally inaccurate and fail to provide reliable estimates of the TAP-based markers in some critical conditions. Conclusions. Highly reliable repolarization sequences can be derived from the extracellular RT markers. Moreover, the HMAP-based markers may offer a reliable alternative for estimating the TAP-based markers when the EG- based markers fail.