UC San Diego

The cardiovascular system is regulated through numerous control systems, which operate on various time scales. The baroreflex operates on the scale of seconds to minutes, responding to acute changes in pressure by altering heart rate, heart contractility, and blood vessel diameter. Blood volume control operates on a time scale of minutes to hours, in which the kidneys regulate blood pressure by means of blood plasma osmolarity and volume in the circulatory system. When pressure is altered on a longer time scale of days to years, growth and remodeling occur in the heart and blood vessel walls.

In this thesis, a multi-scale model was created to improve the capacity for study of the summed or individual effects of different time scales. This time scale consideration resulted in a more physiological approach to modeling the cardiovascular system than previous models. The time scales modeled were an acute seconds-to-minutes scale, during which the baroreflex acts, and a minutes-to-hours scale during which blood volume control occurs. The model was then optimized to allow for future coupling to computationally expensive growth and remodeling models. Arterial pressure regulation was demonstrated in both normal conditions and the pathophysiological condition of aortic valve disease. The work of this thesis successfully reproduced the local effects of the disease, and demonstrated the physiologic response on multiple time scales to the reduction in arterial pressure at an aortic stenosis.