Spectral Analysis of Arterial System Resonance

Abstract

Introduction: The Windkessel model simulates the radial pulse wave. When the aortic valve closes, instead of a pressure decrease during diastole, there is an initial increase due to a resonant response. The aim of this study was to explain this phenomenon based on the spectral analysis, and determine how it is affected by aging. Methods: The Fourier spectrum of resting pressure wave was analysed in a healthy set of 49 young individuals (26.9±7.3 years) and 51 adults (53.4±10.3 years). To explain the results, the Windkessel was considered a low-pass filter composed by distal compliance Cd, aortic inertance L, and peripheral resistance Rp. Results: The spectrum obtained showed a maximum amplitude between 3 and 4 Hz, evidencing resonant behavior in that frequency range. Linear regression of diastolic pressure increases revealed that it depends mainly on the amplitude of the 3rd harmonic of the spectrum (p<0.001), for normal heart rate values. Conclusions: The arterial system resonates at a frequency close to 3.5 Hz, generating the oscillation responsible for the diastolic pressure increase. The resonance frequency remains constant with age, however, the oscillation amplitude, related to small distal artery compliance and endothelial dysfunction, decreases by more than 50%. The resonant configuration of the arterial system results from an evolutionary development that allows diastolic pressure to be increased for approximately 300 ms, using the energy stored during systole. Spectral analysis allows the assessment of aging of the arterial system, and could be useful in evaluating the effects of cardiometabolic diseases on small arteries.