Prediction of aortic augmentation index using radial pulse transmission-wave analysis.
OBJECTIVE
Current arterial transfer functions have low capability in predicting aortic augmentation index (AIx) from radial pulse contour (RPC), because of the difficulty in accurately identifying the merging point (inflection point) in the derived aortic pulse contour (APC). We hypothesize that the formation time between each characteristic wave in APC is about one-third of ejection duration (ED/3). We sought to assess the accuracy of ED/3 in identifying the merging point in APC as compared to the conventional differential method. In addition, we sought to derive the AIx from RPC based on an arterial transfer function and the ED/3 method.


METHODS
APC and RPC sequences were measured digitally and simultaneously in 60 subjects (37 males; aged 60 +/- 10 years). An ensemble-averaged RPC-to-APC transfer function was determined from 30 randomly selected subjects and was used to derive APC sequences in the 30 additional subjects. The accuracy of AIx predicted from RPC was determined.


RESULTS
In patients with a clearly identifiable merging point in APC, the ED/3 method identified the merging point of measured APC within 1.97 +/- 0.60 ms of that identified by the conventional differential method, with identical AIx. The AIx and merging point of derived APC using the ED/3 method were also within 0.22 +/- 1.01% and 1.81 +/- 1.64 ms, respectively, of those of the measured APC using the conventional differential method. The accuracy of the predicted AIx was independent of age, sex, body-mass index and presence of hypertension.


CONCLUSIONS
In a quiet resting state, the ED/3 is an alternative method for identifying the merging point in APC. In conjunction with transfer-function technique, AIx can be derived accurately from RPC.
Department of Medicine, The University of Hong Kong.
Elizabeth O Y
EO
Lau
Hung-Fat
HF
Tse
Raymond H W
RH
Chan
Wai-Hong
WH
Chen
Pui-Yin
PY
Lee
Stephen W L
SW
Lee
Allen T
AT
Chwang
Chu-Pak
CP
Lau
D000328:Adult; D000368:Aged; D001011:Aorta / Q000503:physiopathology*; D015992:Body Mass Index; D005260:Female; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011674:Pulse / Q000379:methods*; D017534:Radial Artery / Q000503:physiopathology*; D015203:Reproducibility of Results