Computer simulation of heart-pacemaker interaction.

The electrical interaction between the heart and an artificial pacemaker is often complex. Because of the sophistication and variability of dual-chamber device algorithms, even experienced cardiologists have difficulty interpreting paced electrocardiograms (ECGs). To study heart-pacemaker interaction (HPI), a computer model of the cardiac conduction system has been developed which includes the effects of artificial pacemaker function and failure. The cardiac conduction model, based upon automata theory, consists of nine vertices each representing a functional electrophysiological element. Connections between vertices include normal and accessory, anterograde and retrograde pathways. Electrophysiological multidimensional conditional probability functions determine the depolarization status of each vertex. A depolarization event occurs at a vertex if its probability of occurrence at time t is greater than a pseudorandom number. The atrioventricular (AV) node is emulated using a mathematical model that includes the inlluence of past cycle lengths on AV nodal conduction time. Twentyfive classes of arrhythmias may be simulated and any one of 12 antibradycardia pacing modes and 6 electrophysiology study protocols may be chosen.