Imaging and modeling the cardiovascular system

Abstract: Understanding cardiac pumping function is crucial to guiding diagnosis, predicting outcomes of interventions, and designing medical devices that interact with the cardiovascular system.  Computer simulations of hemodynamics can show how the complex cardiovascular system is influenced by changes in single or multiple parameters and can be used to test clinical hypotheses. In addition, methods for the quantification of important markers such as elevated arterial stiffness would help reduce the morbidity and mortality related to cardiovascular disease.The general aim of this thesis work was to improve understanding of cardiovascular physiology and develop new methods for assisting clinicians during diagnosis and follow-up of treatment in cardiovascular disease. Both computer simulations and medical imaging were used to reach this goal.In the first study, a cardiac model based on piston-like motions of the atrioventricular plane was developed. In the second study, the presence of the anatomical basis needed to generate hydraulic forces during diastole was assessed in heathy volunteers. In the third study, a previously validated lumped-parameter model was used to quantify the contribution of arterial and cardiac changes to blood pressure during aging. In the fourth study, in-house software that measures arterial stiffness by ultrasound shear wave elastography (SWE) was developed and validated against mechanical testing.The studies showed that longitudinal movements of the atrioventricular plane can well explain cardiac pumping and that the macroscopic geometry of the heart enables the generation of hydraulic forces that aid ventricular filling. Additionally, simulations showed that structural changes in both the heart and the arterial system contribute to the progression of blood pressure with age. Finally, the SWE technique was validated to accurately measure stiffness in arterial phantoms.