Abstract
During aging, systolic blood pressure continuously increases over time, whereas diastolic pressure first increases and then slightly decreases after middle age. These pressure changes are usually explained by changes of the arterial system alone (increase in arterial stiffness and vascular resistance). However, we hypothesise that the heart contributes to the age-related blood pressure progression as well. In the present study we quantified the blood pressure changes in normal aging by using a Windkessel model for the arterial system and the time-varying elastance model for the heart, and compared the simulation results with data from the Framingham Heart Study. Parameters representing arterial changes (resistance and stiffness) during aging were based on literature values, whereas parameters representing cardiac changes were computed through physiological rules (compensated hypertrophy and preservation of end-diastolic volume). When taking into account arterial changes only, the systolic and diastolic pressure did not agree well with the population data. Between 20 and 80 years, systolic pressure increased from 100 to 122 mmHg, and diastolic pressure decreased from 76 to 55 mmHg. When taking cardiac adaptations into account as well, systolic and diastolic pressure increased from 100 to 151 mmHg and decreased from 76 to 69 mmHg, respectively. Our results show that not only the arterial system, but also the heart, contributes to the changes in blood pressure during aging. The changes in arterial properties initiate a systolic pressure increase, which in turn initiates a cardiac remodelling process that further augments systolic pressure and mitigates the decrease in diastolic pressure.
Highlights
Blood pressure changes with age [1]
While cardiac hypertrophy stemming from these arterial changes is widely recognized and reported, the effects of the hypertrophy on blood pressure have not been taken into account quantitatively
The systemic arterial tree is represented by the four-element Windkessel model [10], which has as its model parameters total arterial compliance (C) representing the inverse of arterial stiffness, vascular resistance (R), aortic characteristic impedance (Zc) and total inertance (L)
Summary
Blood pressure changes with age [1]. During normal aging, without drug treatment, systolic blood pressure continuously increases over time, whereas diastolic pressure increases between 20 and 50 years of age, and decreases slightly after the age of 55 [1,2]. Pulse pressure (the difference between systolic and diastolic pressure) increases over the entire period from 20 to 80 years of age [1]. The increase in pulse pressure is mainly due to stiffening of the large arteries [3], and accelerates in later years [4]. Changes in arterial properties that result in a systolic pressure increase induce ventricular remodelling, affecting cardiac structure and function [6,7,8]. The typical form of ventricular remodelling observed with increased afterload is concentric hypertrophy. This type of remodelling results in an increased muscle cross-sectional area that, in turn, increases pump function and has been shown to generate an additional increase in blood pressure [9]. While cardiac hypertrophy stemming from these arterial changes is widely recognized and reported, the effects of the hypertrophy on blood pressure have not been taken into account quantitatively
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