The derivation of the ascending aortic - carotid pressure transfer
function with an arterial model.
Karamanoglu, Mustafa, and Michael P. Feneley.
Cardiology Department and Victor Chang Cardiac Research Institute,
St Vincent's Hospital, Darlinghurst, New South Wales, Sydney,
Australia 2010
APStracts 3:0271H, 1996.
To devise a method of deriving the ascending aortic pressure waveform
from the non-invasively determined carotid arterial waveform, both
were recorded in 13 subjects aged 58.5+/-10.0 (SD) years. A single
viscoelastic tube terminated with a modified windkessel was used to
model the carotid arterial system. For each patient, the model
parameters, characteristic impedance of the tube (Zo), reflection
coefficient at the termination (RF) and the time constant of the
windkessel (Tau), were estimated by minimising the root-mean-square
-error between the measured carotid (CAM) and predicted carotid (CAP)
waveforms with the ascending aortic pressure waveform as input. The
resulting arterial parameters were realistic: Zo= 729.5+/-246.8
dyne.sec/cm3, RF= 0.75+/-0.19, Tau = 0.16+/-0.17 s. A generalised
model constructed with these mean parameters yielded smaller error
between CAP and CAM (3.4 +/- 1.3 mmHg) than between ascending aortic
pressure and CAM (4.4 +/- 1.6 mmHg, p<0.01), and also reproduced
the carotid wave contour indexed by the ratio of late systolic to
early systolic peak amplitude: predicted 1.26 +/- 0.05, measured 1.24
+/- 0.16 versus aortic 1.55 +/- 0.19.
Received 14 June 1996; accepted in final form 14 June 1996.
APS Manuscript Number H152-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 4 July 96