High fidelity, biophysical computer models of cardiac electrophysiology (EP) can help assess conduction mechanisms and plan clinical procedures. However, computational costs mean they are not tools for interacting with cardiovascular implantable electronic devices (CIED) in real-time closed loop. While alternative models have been tested, none successfully encode the EP dynamics generating complex sensing electrograms for CIEDs. The objective of this study is the design and implementation of real-time cardiac EP and conduction dynamics models of diseased hearts for analyzing CIED performance in closed loop.
A robust hybrid-automata modeling approach is adapted to EP and activation dynamics. This is deployed on conduction networks derived from CT images. The EP verified models express nodal tissues, Purkinje networks and ventricular fiber rotation. They execute on a Simulink® platform and are seamlessly deployed to real-time target machines and interface circuits for hardware-in-the-loop interaction with CIEDs. This is a Paced Automata model of Cardiac Electrophysiology in Real time (PACER).
Patient-derived PACER models run continuously in predictable real-time. An example with 943 points and 2820 edges, takes 20.8±0.5s to simulate 30s of EP in normal and abnormal rhythms and provides atrial and ventricular electrograms at guaranteed 1kHz frequency. Sinoatrial and atrio-ventricular EP exhibits autorhythmic properties, dynamic overdrive suppression and vagal activity. The EP and conduction paths are modified to capture heart failure morphology and dynamics. Complex, long runs of arrhythmia present rich sensing electrograms to DDD mode pacemaker algorithms which in turn introduce new pacing signals into the system. With physical hardware-in-the-loop, model-hardware latency is around 5 ms.
PACER models give new insights into CIED timing interactions with normal and diseased heart rhythms. Clinical scenarios can be replayed and alternative timing parameters explored. The interactive paradigm can also be deployed to assess other interventions altering EP circuits, such as ablation.