ECHO 2013 / Pediatric Echocardiography Overview of Quantification and Lessons Learned
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Allometry
•Allometry is the study of the relationship of body size to shape, anatomy, physiology and behavior.
J Appl Physiol 2005;99:455-7
•“Body surface area (BSA) was found to be a more important determinant of the size of each of the cardiovascular structures than age, height, or weight alone.”
Cardiovascular Allometric Relationships
Sluysmans and Colan 2005
•Assumption:
–Without stenosis, the volume of flow is the primary determinant of vessel and valve size
•Findings:
–Observed dimensions in agreement with predicted values based on the principle of minimum work
Cardiovascular Allometric Relationships
Sluysmans and Colan 2005
Total Energy Loss/Second
QS = 3.5 l/min
Total Energy Loss/Second
QS = 17.5 l/min
Viscous friction energy loss per second = dashed line (drops with size)
Inertial energy content of blood loss = dasheddotted line (rises with size)
Total energy loss (red line) least at aortic radius of 0.45 cm (3.5 l/min) to 0.8 cm (17.5 l/min) for BSA of 1 m2
Cardiovascular Allometric Relationships
Sluysmans and Colan 2005
Vascular dimensions appear optimized to accommodate the cardiac output associated with peak normal activity.
Cardiovascular Allometric Relationships
Sluysmans and Colan 2005
•Findings:
–BSA better than age, height, or weight alone
–Vessel and valve dimensions related linearly to BSA0.5
–Vessel and valve areas related to BSA1.0
–RV and LV volumes correlated to BSA and CO; volumes related to BSA1.4
Cardiovascular Allometric Relationships
Sluysmans and Colan 2009 (Lai et al. textbook)
For linear dimensions, indexing to BSA0.5 resulted in a linear relationship with a zero intercept, but…
Cardiovascular Allometric Relationships
Sluysmans and Colan 2009 (Lai et al. textbook)
the residual data spread still varied as a function of body surface area.
Heteroscedasticity
•A nonconstant variance of error has been shown for almost all echocardiographic measures
•Multiple equations in overlapping segments and smoothing function using Lambda Mu
Sigma (LMS) method
Z-Scores
•Z-score = method of adjusting a measure for age or body size relative to the distribution of structure in a normal population
–Z-score of 0 = value at the mean of a normal population
–Z-score of 1 = value at 1 SD above the mean of a normal population
–Z-score of -1 = value at 1 SD below the mean of a normal population
Normal Pediatric Datasets
JACC 1992
Boston
Pediatr Cardiol 2005
Cincinnati
JASE 2004
JASE 2008
Detroit
JASE 2009
DC
Texas