A Systematic Review of Scaling Left Atrial Size: Are Alternative Indexation Methods Required for an Increasingly Obese Population?

Background: Left atrial (LA) size indexed to body surface area (BSA) is a clinically important marker of cardiovascular prognosis. However, indexation using a scaling variable such as BSA has inherent flaws, particularly in an obese population. The aim of this study was to determine whether alternative indexation methods may more accurately scale for LA size.

Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were used to execute a structured search of medical databases, to identify articles discussing alternative methods of LA indexation in echocardiography. Articles that stratified indexed LA size by obesity class were also included. Two independent reviewers identified relevant articles and extracted baseline characteristics, alternative indexation methods, scaling variables, obesity class characteristics, and correlation coefficients.

Results: A total of 3,804 articles were found in the database search after removing duplicates. After abstract and full-text screening, 13 relevant articles were identified. Twelve studies used alternative methods of LA indexation, of which nine reported allometric indices. Seven of the included studies reported LA size by obesity class, of which six reported alternative indices. Correlation coefficients plotted for indexed LA size against absolute measured LA size showed that allometric indices (specifically to height) were more likely to maintain proportionality to body size compared with isometric indices such as BSA. Allometric indices were less likely to overcorrect for body size compared with isometric indices.

Conclusions: Compared with isometric indexation to BSA, allometric indexation (specifically to height) improves scaling of LA volumes to maintain proportionality and avoid overcorrection for body size.