Optimized design of an arterial network model reproduces characteristic central and peripheral haemodynamic waveform features of young adults. (2nd August 2022)

• Record Type: Journal Article
• Authors: Kondiboyina, Avinash; Harrington, Hilary A.; Smolich, Joseph J.; Cheung, Michael M. H.; Mynard, Jonathan P.
• Is Part Of: Journal of physiology. Volume 600:Number 16(2022)
• Page Start: 3725
• Page End: 3747
• Publication Date: 2022-08-02
• Subjects: arterial haemodynamics -- cardiovascular modelling -- wave reflection; Physiology -- Periodicals; 612.005
• DOI: 10.1113/JP282942
• Languages: English
• ISSNs: 0022-3751

Abstract

Abstract : Abstract: The arterial network in healthy young adults is thought to be structured to optimize wave reflection in the arterial system, producing an ascending aortic pressure waveform with three key features: early systolic peak, negative systolic augmentation and diastolic hump. One‐dimensional computer models have provided significant insights into arterial haemodynamics, but no previous models of the young adult have exhibited these three features. Given that this issue was likely to be related to unrepresentative or non‐optimized impedance properties of the model arterial networks, we developed a new 'YoungAdult' model that incorporated the following features: (i) a new and more accurate empirical equation for approximating wave speeds, based on area and relative distance to elastic–muscular arterial transition points; (ii) optimally matched arterial junctions; and (iii) an improved arterial network geometry that eliminated 'within‐segment' taper (which causes wave reflection in conduit arteries) whilst establishing 'impedance‐preserving' taper. These properties of the model led to wave reflection occurring predominantly at distal vascular beds, rather than in conduit arteries. The model predicted all three typical characteristics of an ascending aortic pressure waveform observed in young adults. When compared with non‐invasively acquired pressure and velocity measurements (obtained via tonometry and Doppler ultrasound in seven young adults), the model was also shown to reproduce the typical waveform morphology observed in the radial, brachial, carotid, temporal, femoral and tibial arteries. The YoungAdult model provides support for the concept that the arterial tree impedance in healthy young adults is exquisitely optimized, and it provides an important baseline model for investigating cardiovascular changes in ageing and disease states. Key points: The origin of wave reflection in the arterial system is controversial, but reflection properties are likely to give rise to characteristic haemodynamic features in healthy young adults, including an early systolic peak, negative systolic augmentation and diastolic hump in the ascending aortic pressure waveform, and triphasic velocity profiles in peripheral arteries. Although computational modelling provides insights into arterial haemodynamics, no previous models have predicted all these features. An established arterial network model was optimized by incorporating the following features: (i) a more accurate representation of arterial wave speeds; (ii) precisely matched junctions; and (iii) impedance‐preserving tapering, thereby minimizing wave reflection in conduit arteries in the forward direction. Comparison with in vivo data ( n = 7 subjects) indicated that the characteristic waveform features in young adults were predicted accurately. Our findings strongly imply that a healthy young arterial system is structured to optimize wave reflection in the main conduit arteries and that reflection of forward waves occurs primarily in the vicinity of vascular beds. Abstract : Abstract figure legend In this paper, three key improvements were implemented in a one‐dimensional (1D) model of the systemic arterial network. (1) Wave speed was represented better by accounting for differences between elastic and muscular arteries via transition points. (2) Continuous arterial taper was replaced with stepwise reduction in diameter via well‐matched side‐branches. (3) Vascular bed compliance was modified to achieve triphasic flow in peripheral arteries. These improvements produced an ascending aortic pressure waveform with three features typical of a healthy young adult: an early systolic peak, negative augmentation and a diastolic hump.