Indexing of left atrial volume by body surface area and height in a
Brazilian population without previous heart disease and with a normal
heart on echocardiography. Behavior in obese and overweight patients.
Abstract
Background: Left atrial (LA) volume indexing for body surface area (BSA)
may underestimate LA size in obese and overweight people. Since LA
volume is a risk marker for some cardiovascular events, it is suggested
that indexing for height would be an alternative more apropriated
method. The aims of this study were to find normal and the best cutoff
values for LA volume indexed for height in our population. Methods:
Echocardiograms from 2018 to 2021 were reviewed and patients without
known cardiac disease and completely normal echocardiograms that had the
left atrial volume (LAvol) measured by biplane Simpson’s method were
included. LAvol was indexed by BSA (ml/m²), by height (LAvol/m), by
height raised to exponent 2.7 (ml/ m2.7) and by height squared (ml/h²).
Results: A total of 545 patients, 50.5 ± 13.4 y., 335 females (61,5%)
were analyzed. There were 145 normal weight (26.6%), 215 overweight
(39.4%), 154 obese (28.3%) and 31 low weight (5.7%) patients. To
estabilish normal values we included only the normal weight group and
considered normal values from 2SD below to 2SD above the mean. Mean and
normal values were: LAvol/h 26.0 ±4.5, 17 – 30 ml/m, LAvol/ht² 16 ±
2.8, 10.4 - 21.6 ml/ ht² and LAvol/ht2.7 11.4 ± 2.2, 7.0 - 15.8 ml/m2.7.
The normal LAvol/ht2.7 differed between male and female (11.4 ± 2.4 and
12.8 ± 2.6, p = 0.000). LA diameter, LAvol, LAvol/h, LAvol/h² and
LAvol/ht2.7 increased progressively from low-weight, normal weight,
overweight and obese patients (p= 0.0000), but not LAvol/BSA. When
indexing LAvol for height, for height² and for height2.7 20.8%, 22.7%
and 21.4% of the obese patients, respectively, were reclassified as
enlarged LA, and 7.4%, 8.8% and 8.4% of the overweight patients as
well. Using ROC curve analysis, LAvol/h² had the highest AUC ant the
best predictive value to identify LA enlargement and LAvol/BSA the worst
one. Conclusions: normal values for LAvol indexed for height by three
different methods are described in normal individuals. We reinforce that
LAvol indexation for BSA underestimates LA size in obese and overweight
patients and in these groups, specially, indexing for height² is
probably the best method to evaluate LAvol.