CVSim is a lumped-parameter model of the human cardiovascular system that has been developed and used for research and for teaching quantitative physiology courses at MIT and Harvard Medical School since 1984. We present a brief historical background of lumped-parameter cardiovascular system models, followed by an overview of the development of the major versions of CVSim over a 25-year period in our laboratory. We describe the features and differences of four versions of CVSim that are freely available in open-source form via PhysioNet (http://physionet.org). These include a six-compartment cardiovascular model with an arterial baroreflex system, implemented in C for efficiency, with an X-based graphical user interface; a six-compartment model with a more extensive short-term regulatory system and incorporating resting physiologic perturbations, available as a stand-alone MATLAB application; and a pair of elaborated versions consisting of 6- and 21-compartment computational models implemented in C, with a separate and enhanced Java graphical user interface. We conclude with a discussion of the educational and research applications for which we have used CVSim.
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