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Extrapolation of cardiac index from analysis of the left ventricular outflow velocities in children: implication of the relationship between aortic size and body surface area
Author(s) -
Wodey Eric,
Senhadji Lotfi,
Carre François,
Ecoffey Claude
Publication year - 2002
Publication title -
pediatric anesthesia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.704
H-Index - 82
eISSN - 1460-9592
pISSN - 1155-5645
DOI - 10.1046/j.1460-9592.2002.00834.x
Subject(s) - body surface area , medicine , ventricular outflow tract , linear regression , cardiology , aorta , extrapolation , aortic valve , nonlinear regression , linear relationship , regression analysis , statistics , mathematics
Background : It has recently been reported in critically ill patients that a linear relationship exists between cardiac index (CI) measured with thermodilution and mean aortic blood flow velocity (MAFV). This hypothesis can be validated mathematically only if the aortic area (AA index ) indexed to body surface area (BSA) remains constant and if the relationship between aortic diameter (ØAo) and BSA is nonlinear. However, several other equations have described the relationship between BSA and, respectively, ØAo and aortic area (AA) in children. The aim of this study was to determine if the relationships calculated between BSA and aortic size in children (without left ventricular outflow tract abnormality) could validate the hypothesis that MAFV and CI are well linked linearly, leading to its use to determine CI. Methods : Two hundred and thirty‐two measurements performed in 126 children and infants were retrospectively analysed. ØAo was measured in the long axis view at the annulus using two‐dimensional mode echocardiography with a 5‐MHz transducer. Various linear and nonlinear relationships between BSA and, respectively, ØAo, ØAo index , AA and AA index were determined based on a nonlinear regression method with a model as follows: y = a ( x c ) + b . The comparisons between regressions were conducted based on the estimation error. Results : The relationships between ØAo and BSA appeared nonlinear and was well described by: ØAo=2.96(BSA 1/4 ) – 1.31 with a non‐zero y ‐intercept and ØAo=1.64(BSA 1/2 ) with a zero y ‐intercept. In contrast, the relationships between AA and BSA were linear. The AA index was not linked to BSA and can be considered as constant. The coefficient a of the equation appeared similar to those obtained mathematically with the relationship previously described between MAFV and CI. Conclusions : The hypothesis that CI can be extrapolated to the measurement of MAFV appears valid as regards the relationships calculated between aortic size and BSA in children without left ventricular outflow tract abnormality.