A Technical Assessment of Pulse Wave Velocity Algorithms Applied to Non-invasive Arterial Waveforms
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A Technical Assessment of Pulse Wave Velocity Algorithms Applied to Non-invasive Arterial Waveforms N. R. GADDUM,1 J. ALASTRUEY,1 P. BEERBAUM,2 P. CHOWIENCZYK,3 and T. SCHAEFFTER1 1 Division of Imaging Sciences and Biomedical Engineering, St. Thomas’ Hospital, King’s College London, London, UK; Department of Pediatric Cardiology & Pediatric Intensive Care Medicine, Hannover Medical School, Hannover, Germany; and 3 St Thomas’ Hospital, King’s College London British Heart Foundation Centre, London, UK
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(Received 6 March 2013; accepted 20 June 2013) Associate Editor Nathalie Virag oversaw the review of this article.
Abstract—Non-invasive assessment of arterial stiffness through pulse wave velocity (PWV) analysis is becoming common clinical practice. However, the effects of measurement noise, temporal resolution and similarity of the two waveforms used for PWV calculation upon accuracy and variability are unknown. We studied these effects upon PWV estimates given by foot-to-foot, least squared difference, and cross-correlation algorithms. We assessed accuracy using numerically generated blood pressure and flow waveforms for which the theoretical PWV was known to compare with the algorithm estimates. We assessed variability using clinical measurements in 28 human subjects. Wave shape similarity was quantified using a cross correlation-coefficient (CCCoefficient), which decreases with increasing distance between waveform measurements sites. Based on our results, we propose the following criteria to identify the most accurate and least variable algorithm given the noise, resolution and CCCoefficient of the measured waveforms. (1) Use foot-to-foot when the noise-to-signal ratio £10%, and/or temporal resolution ‡100 Hz. Otherwise (2) use a least squares differencing method applied to the systolic upstroke. Keywords—Pulse wave velocity, Foot to foot, Least squares, Cross correlation, Doppler ultrasound, Tonometry, Onedimensional modelling.
INTRODUCTION Pulse wave velocity (PWV) is highly predictive of mortality and morbidity from cardiovascular disease.22 This is attributed to PWV being a measure of arterial ageing and/or adverse haemodynamic effects imposed on the heart and brain by stiffening of the great arteries. Significant research focus, therefore, is Address correspondence to N. R. Gaddum, Division of Imaging Sciences and Biomedical Engineering, St. Thomas’ Hospital, King’s College London, London, UK. Electronic mail: nickgaddum@ gmail.com
directed toward techniques to measure PWV accurately in the wider population using non-invasive haemodynamic waveforms.21 Non-invasive assessment of central PWV has been achieved by processing arterial pressure, luminal area, or blood velocity waveforms. Traditionally, PWV is calculated as space-averaged parameter by measuring the arterial path length and the transit time (TT) between two waveforms measured at different sites.12 Despite extensive use of the method, there is little agreement on the technical aspects of how to actually determine the TT between two physiological wavefo
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