Non-invasive 24 hour ambulatory monitoring of aortic wave reflection and arterial stiffness by a novel oscillometric device: The first feasibility and reproducibility study

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Abstract

Background

Surrogates of aortic wave reflection and arterial stiffness, such as augmentation index (AIx), augmentation pressure, pulse wave velocity (PWV) and pulse pressure amplification (PPampl) are independent predictors of cardiovascular risk. A novel ambulatory, brachial cuff-based oscillometric device has been recently developed and validated, yielding 24-h assessment of the aforementioned parameters (Mobilo-O-Graph). Aim of this study was to investigate the feasibility and reproducibility of wave reflection and arterial stiffness estimation by pulse wave analysis using this device.

Methods

Thirty treated or untreated hypertensives (mean age: 53.6 ± 11.6 years, 17 men) had test–retest 24-h monitoring one week apart using the test device.

Results

Mean numbers of valid aortic readings per subject, between test and retest, were comparable. Approximately 12 aortic readings per subject (17%) were not feasible or valid. No differences were observed for any 24-h parameter between the two assessments. Bland–Altman plots showed no systemic difference, while the limits of agreement for each parameter indicated high reproducibility (AIx: − 7.2 to 8.2%, AP: − 3.7 to 4.1 mm Hg, PWV: − 0.39 to 0.41 m/s, PPampl: − 0.08 to 0.06). This was further verified by intraclass correlation coefficients which were > 0.8 for each parameter.

Conclusions

Non-invasive 24-h estimation of wave reflection and arterial stiffness indices, derived by the test device, appear to be highly reproducible. Future studies should investigate whether these measurements have additive prognostic value for cardiovascular risk stratification, beyond common brachial blood pressure measurements or single estimations of wave reflection and PWV at office settings.

Introduction

Arterial pulse has been recognized as a fundamental vital sign since antiquity. From the pioneering observations of William Harvey in 1960s [1], to recent developments in biomedical engineering and bioinformatics, the arterial pressure wave constitutes an unfailing source of information in research and clinical fields. Currently, several other biomarkers/parameters beyond maximum, minimum, mean values of pressure waves (namely systolic, diastolic, and mean pressure) can be derived by pulse wave analysis (PWA). Particularly, parameters characterizing wave reflection phenomena (i.e. augmentation index, reflection magnitude), arterial stiffness (most commonly assessed by pulse wave velocity), and the difference between central and peripheral pulse pressure (PP) defined as PP amplification, have been extensively investigated and proved to be independent predictors of cardiovascular morbidity and mortality [2], [3], [4], [5], [6].

In the last decades the non-invasive estimation of pressure wave parameters at central arteries (i.e. aorta, carotid artery) has been achieved [7], aiming to assess the hemodynamic profile at sites closer to target organs (heart, brain, and kidneys) compared to the brachial artery. However, PWA modalities offered only instantaneous measurements of the aforementioned parameters at the office/clinic or at home, until recently when 24-h ambulatory recording and measurement of PWA parameters has become feasible [8]. A novel device has been developed yielding multiple peripheral and aortic BP readings together with estimations of wave reflection and arterial stiffness during usual daily activities, including sleep. This technology offers a far better representation of the “central hemodynamic burden” than what is obtained by a few measurements taken in the doctor's office.

Considerable evidence is now available from longitudinal studies indicating that ambulatory blood pressure monitoring (ABPM) is a much stronger predictor of cardiovascular morbidity and mortality than conventional office measurement [9], [10], [11]. The respective 24-h monitoring of wave reflection and arterial stiffness parameters is expected to further enhance the diagnostic evaluation and optimize CV risk management.

Although technology for 24-h ambulatory monitoring of central hemodynamics is now available, the feasibility and reproducibility of central PWA parameters is still unexplored. The purpose of the present study was to investigate the feasibility and reproducibility of non-invasive assessment of aortic hemodynamic parameters using a novel non-invasive 24-h ambulatory cuff-based oscillometric technique.

Section snippets

Study design and population

From January to June 2011 consecutive subjects referred to Hypertension Clinics of two University Departments at “Laiko” and “Sotiria” hospitals, Athens, Greece were recruited. The study protocol and the examined population have been previously described [12]. Inclusion criteria were: age > 18 years, stable cardiovascular condition and unchanged cardiovascular medication for at least 2 months. Exclusion criteria were the presence of atrial fibrillation and modification of any vasoactive drug

Results

The demographic characteristics of the study population have been previously published [12] and are briefly presented herein (Table 1). The time intervals between day-1 and day-2 ranged from 1 to 6 weeks.

Discussion

The present study is the first that investigated the feasibility and reproducibility of non-invasive 24-hour ambulatory monitoring of wave reflection and arterial stiffness characteristics estimated using a novel automated, portable brachial cuff-based, oscillometric device. The results suggest that the estimation of wave reflection and arterial stiffness parameters on a 24-h basis is feasible and the calculated parameters by this apparatus are highly reproducible.

All aortic hemodynamic

Conclusions

The relevance of instantaneous measurements of wave reflection as well as arterial stiffness parameters is now indisputable [3], [32], [33]. However, there is an inherent variation of wave reflection, arterial stiffness and BP amplification during the day as shown by previous studies performing manual (non-automated) multiple measurements [34], [35], [36]. Environmental, life style, physiologic and more importantly pathologic and pharmacologic factors may affect the 24-h variability pattern of

Acknowledgments

The Mobil-O-Graph devices used in this study were kindly provided by IEM.

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    Funding: None.

    1

    TGP and AA contributed equally to the manuscript.

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