Computer model for simulation of first transit cardiac radionuclide curves--I.

A discrete-time, lumped-parameter mathematical model of the human cardiopulmonary circulation as it appears during a first-transit radionuclide study is developed. Eleven compartments, four delays, and 26 transfer paths are modeled, including the entire circulation from an input compartment before the vena cava to an output compartment after the aorta. The 26 transfer paths include forward and reverse flow through the heart valves, backflow from the atria into the veins, and five types of shunts. A method of modeling continuously-variable delay segments with only discrete-time sample points is devised to allow more versatility in specifying delays. The model simulates discrete time-activity curves for the various compartments of the cardiopulmonary system. The curves are obtained for end-systole and end-diastole. Simulation of curves indicative of a normal heart and several heart defects is presented. The use of this model for computer analysis of first-transit cardio-radionuclide curves is discussed.