1050-2 Computer Modeling for Real-time Interactive Demonstration of Reentry and Induction of Tachycardia: A Teaching Tool

The induction and termination of reentrant tachycardia are difficult to conceive with electrograms only. An interactive computer model based on conduction and refractory time is constructed for real-time simulation of reentry. Written in Microsoft C+ + v. 6.0, 2 pathways (Pl, P2) connected at both ends (A, V) are created. There are 2 cells at each end and 7 cells in each pathway (Figure). There is 1 simulated electrogram each for surface ECG, atrium, the 2 pathways, and ventricle. The cell “on” time (I). “off” time (O), and stimulation threshold can be changed. The cells are in a “ready” state when they are not “on” or “off”, with different designated colors. The model can be “paced” from the pacelsense cells with various coupling intervals (C), and the cells will be sequentially turned “on” after I of the preceding cell, if they are “ready”. After I, the cells become “off” for the duration of O (i.e. refractory time) before returning to “ready”. The simulated electrograms in the respective channels show the P (or A) and ORS (or V) waves corresponding to the “on” state of the pacelsense cells. The “surface ECG” also shows T waves during the “off” state of the Vend. The sum of I of the 7 cells determines the pathway conduction time. 1 of the 2 pathways can also be determined by an equation to simulate the properties of the atrioventricular node: I = AH∞ + D * exp(-C/τ). I and C represent the A 2 H 2 and A 1 A 2 intervals respectively, AH∞ is the asymptotic cycle length approached as A 1 , A 2 increases, and D and τ are constants. AH ∞ , D, and τ obtained from curve fitting can be changed to simulate clinical cases. Decremental pacing or extrastimuli can induce or terminate reentrant tachycardia of the computer, as seen from the propagation of cell activation and the simulated electrograms. Conclusion It is feasible to create an interactive computer model for real-time simulation of reentry based on the conduction and refractory time of 2 pathways. This model can be a useful teaching tool for reentry. Download high-res image (38KB) Download full-size image