Computer-based Interpretation of Intracardiac Electrograms: Identifying Rhythm Mechanisms from Ventricular Extrastimulus Tests

Introduction: computer-based system for analyzing complex cardiac rhythms is being developed in our laboratory. The system analyzes rhythms by adapting and simulating one or more semi-quantitative electrophysiologic models based on sequence of events (P waves, QRS complexes, His bundle potential, etc.) on an event-by-event basis. The electrophysiologic model developed for the system can represent anatomies consisting of up to 4 accessory pathways, up to 3 AV nodal slow pathways, and 1 Mahaim pathway. We hypothesized that this system can (1) generate the correct electrophysiologic model(s) based on the observed events, (2) correctly differentiate between AV Nodal Reentrant Tachycardi (AVNRT), AV Reentrant Tachycardi (AVRT), and Atrial Tachycardi (ATACH) based on intracardiac electrogram dat obtained during ventricular extrastimulus pacing protocols, and (3) generate ladder diagrams describing the identified rhythm mechanisms. Methods: Typical cases were identified for each of the desired rhythms (AVNRT, AVRT, and ATACH). Using software written in our lab, the cases were annotated to extract wave timing and morphology from the body-surface electrocardiogram and wave timing of the high right atrial, His bundle, and right ventricular intracardiac electrograms. Due to the anatomic complexity underlying reentrant tachyarrhythmias, we developed novel algorithms for enumerating the complete set of conduction paths through complex electrophysiologic models. We also developed the logic necessary for reasoning with multiple model paths and simultaneous activation of anatomically distinct model regions. The system was developed in C on UNIX workstation and runs on UNIX workstations or IBM PC-compatible computers. Results: In all cases, the system (1) generated the correct set of electrophysiologic models, (2) eliminated or supported the appropriate models (i.e. rhythm mechanisms) based on the ventricular extrastimulus, and (3) generated ladder diagrams describing the rhythm mechanisms. Conclusions: This is the first report of computer-based system capable of deriving differential diagnoses with supporting ladder diagrams from intracardiac electrogram recordings. This demonstrates the potential for automatic analysis of complex rhythms by computer-assisted analysis of intracardiac electrograms. This system may be useful in the clinical electrophysiology laboratory by assisting physicians with the enormous amount of dat generated during the typical electrophysiology study.