P-279: Anomalies of wave reflection phenomena in clinical studies

Abstract

Pulse waveform analysis is contentious, with spirited debate between investigators who use a generalised transfer function to generate the aortic waveform from the radial pressure pulse, and those who rely on non-invasive measurement of the carotid pressure waveforms, or invasive measurement of the aortic waveform with fluid-filled catheter systems. The present report seeks to clarify this issue.

In a cohort of 999 patients attending a clinical cardiovascular outpatient service, pressure waveforms were measured non-invasively in the radial artery (8917 reports), with the ascending aortic pressure waveform generated by SphygmoCor®. Results for key parameters Tr (time from wave foot to onset of reflected wave) and AIx (augmented pressure/pulse pressure) were compared with those in the literature, and specifically with the Australian National Blood Pressure (ANBP2) substudy of carotid waveforms¹ and another which analysed invasively recorded aortic waveforms².

Data generated in this study from the radial pressure waveforms were similar to seminal data , but different to those in other Australian carotid and aorta studies. For the ANBP2 study¹, the average value of Tr (80 msec) was very short, and lower than any value recorded by us (lowest 89 msec) while AIx was higher, often exceeding 50%, which indicates reflected wave amplitude greater than incident wave. In contrast, for the aortic pressure waves of Hope et al², average Tr (161 msec) was far higher, and AIx far lower (14.4%) than the ANBP2 study, while our data and that of Murgo et al³ were intermediate. (See Table)

	Radial-aortic TF	Murgo et al3 (A)	Carotid1	Aorta2
N	999	7	873	78
Age (years)	66 ± 15	40	72	64
Tr (msec)	140 ± 14	136	80	161
AIx (%)	25 ± 13	23	34	14

TF; transfer function.

Differences in manifestations of wave reflection in the literature are extreme, and difficult to reconcile with seminal invasive, and current non-invasive studies.

Pulse Waveform Analysis, Generalized Transfer Function, Wave Reflection