Abstract 16148: Calculating Indexed Aortic Root Diameters With Ideal Body Weight Leads to Significant Reclassification in Overweight and Obese Patients

Abstract

Introduction: Indexed Aortic root diameter (AoR diam) measured by transthoracic echocardiography (TTE) using body surface area (BSA) is important in children, adolescents, and small adults in whom non-indexed values may under detect dilation. However, indexed AoR diam may lead to misleading results in obese individuals as the AoR diam does not increase in proportion to body weight. Hypothesis: We hypothesize that using ideal body weight (IBW, using the Devine formula) in place of actual weight in BSA calculation reclassifies a significant proportion of indexed AoR diam in overweight and obese patients. Methods: We performed a retrospective review of all patients with a TTE at Tufts Medical Center in 2022 and Ao root diam >4 cm for men and >3.6 cm for women. We excluded patients < 20 years old and those with inadequate TTE images or missing aortic measurements. TTE data and baseline characteristics were recorded. Indexed AoR diam was calculated using both actual and ideal body weights. The thresholds for for mildly, moderately, and severely dilated indexed AoR were ≥2.2, ≥2.4, and ≥2.6 in men, and ≥2.3, ≥2.4, and ≥2.6 in women, respectively. Results: 456 patients (400 males, 56 females) met our inclusion criteria, with a subset of 331 patients (72.6%) with BMI ≥25. When ideal body weight was used for indexing AoR diam, 58.7% of patients initially classified as having 'normal' indexed AoR diam were reclassified as at least 'mildly dilated' (p<0.001). Patients with a BMI ≥25 were more often reclassified as at least ‘mildly dilated’ compared to those with lower BMI (64.6% vs. 13.3%, p<0.001). In stratified analysis, upward reclassification occurred in 31.9% of patients with 'mildly dilated' AoR diam (45.8% in BMI ≥25) and 35.2% of patients with 'moderately dilated' AoR diam (80% in BMI ≥25). Conclusions: The use of ideal body weight instead of actual body weight for indexing AoR diam changes risk-stratification in over half of the patients with an abnormal AoR. This is more pronounced in patients with a BMI ≥25 and may have significant management implications. Further studies are needed to investigate if the use of actual weight in Ao root indexing systematically underestimates Ao root dilation in overweight and obese patients and if the use of IBW can improve risk assessment.