The authors present a PC-based real-time heart simulator to help design, test, and demonstrate the operation of advanced implantable device features. A PC half-card hardware assembly measures the pacing stimuli and defibrillation pulses from an attached implantable device. It also generates atrial (A) and ventricular (V) intracardiac waveforms to the device which are altered in real-time as either suprathreshold captured or subthreshold noncaptured pacing is detected. The software simulates the electrical interactions between the atria, AV node, and ventricles. Reentrant excitation is modeled via a ring of additional excitable nodes. The PC screen displays the surface or endocardial electrocardiograms and measured parameters such as A-A and V-V event intervals. The operator can initiate synchronous or asynchronous premature events and can interactively alter menu items such as cardiac rhythm, intrinsic rate, retrograde conduction time, pacing and defibrillation thresholds, respiration rate, and tidal volume.
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