This paper describes a universal simulation system which enables simulation models of cardiac rhythm disturbances and of artificial pacemaker actions to be constructed. Three types of heart element are introduced according to the way in which excitation impulses are propagated or produced. Cycle rate dependence of repolarization periods and of impulse transmission speeds is incorporated. Random and predetermined deviations from natural behavior are also allowed for in the model. Using the universal system, a model of simple configuration has been developed. There are five physiological and five pathological heart components joined together by uni- and bidirectional connectors. Additional bidirectional channels allow a variety of pacemakers to be "implanted" in the simulated heart.