Height vs. BSA for Normalization of Ascending Aorta Diameter

Study Questions:

Among patients with thoracic ascending aortic aneurysm (TAAA), how does aortic diameter indexed to patient height (the aortic height index [AHI]) compare with aortic diameter indexed to body surface area (BSA) for the estimation of the risk of aortic dissection, rupture, or death?


Aortic diameters and long-term complications among 780 patients with TAAA were analyzed. Growth rate estimates, yearly complication rates, and survival were assessed. Risk stratification was performed using regression models. The predictive value of AHI and aorta diameter indexed to BSA (aortic size index [ASI]) was compared.


Patients were stratified into four categories of yearly risk of complications based on ASI and AHI. ASI (cm/m2) ≤2.05, 2.08-2.95, 3.00-3.95, and ≥4; and AHIs (cm/m) of ≤2.43, 2.44-3.17, 3.21-4.06, and ≥4.1 were associated with a 4%, 7%, 12%, and 18% average yearly risk of complications, respectively. Five-year complication-free survival was progressively worse with increasing ASI and AHI. Both ASI and AHI were shown to be significant predictors of complications (p < 0.05). AHI categories 3.05-3.69, 3.70-4.34, and ≥4.35 cm/m were associated with a significantly increased risk of complications (p < 0.05). The overall fit of the model using AHI was modestly superior based on the concordance statistic.


Compared with indices that include weight, a simpler height-based ratio (avoiding weight assessment and BSA calculation) yields satisfactory results for evaluating the risk of complications among patients with TAAA.


International guidelines use uncorrected aortic diameter to estimate the risks of aortic dissection, rupture, or death among patients with TAAA. This group previously published data that used aortic diameter indexed to BSA as a more patient-specific predictor of risk. However, especially among obese individuals, weight probably does not play as important a role as does height in indexing various measures to body size. In this study, the authors found that a simpler measure of aortic diameter indexed to height had similar predictive power compared to aortic diameter indexed to BSA. Based on these results, an aortic diameter-to-patient height ratio of ≤2.43 cm/m indicates lower risk, 2.44-3.17 cm/m indicates moderate risk warranting close radiographic follow-up, 3.21-4.06 cm/m indicates high risk, and ≥4.1 cm/m represents severe risk.

Clinical Topics: Cardiac Surgery, Invasive Cardiovascular Angiography and Intervention, Noninvasive Imaging, Prevention, Vascular Medicine, Aortic Surgery, Cardiac Surgery and Arrhythmias, Interventions and Imaging, Interventions and Vascular Medicine

Keywords: Aneurysm, Dissecting, Aortic Aneurysm, Thoracic, Aortic Rupture, Body Size, Body Surface Area, Body Weight, Cardiac Surgical Procedures, Diagnostic Imaging, Dissection, Risk, Secondary Prevention, Vascular Diseases

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