The heart as a self-regulating system: integration of homeodynamic mechanisms*

In the past the study of mechanical and electrical properties of the heart has been disjointed with minimal overlap and unification. The fact remains that these features are tightly coupled and central to the functioning heart. The maintenance of adequate cardiac output relies upon the highly integrated autoregulatory mechanisms and modulation of cardiac myocyte function. Regional ventricular mechanics and energetics are dependent upon muscle fiber stress-strain rate, the passive properties of myocardial collagen matrix, adequate vascular perfusion, transcapillary transport and electrical activation pattern. Intramural hydraulic "loading" is regulated by coronary arterial and venous dynamics. All of these components are under the constant influence of intrinsic cardiac and extracardiac autonomic neurons, as well as circulating hormones. A brief overview of the putative regulation of these various components is presented in this paper.