Allometric Model Improves Scaling of Left Atrial Size in Obese Population: the Use of Body Weight Containing Variables is Challenged

Background: Scaling left atrial (LA) size remains a challenge. An allometric model using body weight (BW) as scaling variable was recently proposed. We sought to examine the performance of this model in an obese population. Methods: A total of 266 consecutive overweight (110) and obese subjects (class I, II, and III obese 81, 47, and 28, respectively) were studied; 46 normal subjects with normal body mass index (BMI) served as controls. LA dimension (LAD) was scaled to BW, body surface area (BSA), BMI and height, respectively, using both isometric and allometric models. Results: There were no significant differences in age, gender, or height among the five groups. The prevalence of comorbid conditions, wall thickness, E/E’ and LAD measures increased significantly with increasing weight group (P < 0.01–0.001). With the isometric model, LAD corrected by BW, BSA, and BMI significantly but paradoxically decreased across the groups (P < 0.05–0.001). With the allometric model, LAD overcorrection by BM, BSA, and BMI was improved, but remained in the class III obese group. In contrast, scaling LAD to height showed significant and graded increase across the five groups in accordance with the increases of BMI, E/E’ and the prevalence of comorbid conditions. Conclusion: All isometric models that correct LAD by BW or BW containing variables underestimate LA size in overweight and obese groups. The allometric model using height provides more consistent results and should be preferred to models using BW or BW containing variables in scaling LAD in obese population. (Echocardiography 2011;28:253‐260)