Adjusting parameters of aortic valve stenosis severity by body size

Adjustment of cardiac dimensions by measures of body size appears intuitively convincing and in patients with aortic stenosis, aortic valve area (AVA) is commonly adjusted by body surface area (BSA). However, there is little evidence to support such an approach.

To identify the adequate measure of body size for the adjustment of aortic stenosis severity.

Parameters of aortic stenosis severity (jet velocity, mean pressure gradient (MPG) and AVA) and measures of body size (height, weight, BSA and body mass index (BMI)) were analysed in 2843 consecutive patients with aortic stenosis (jet velocity ≥2.5 m/s) and related to outcomes in a second cohort of 1525 patients from the Simvastatin/Ezetimibe in Aortic Stenosis (SEAS) study.

Whereas jet velocity and MPG were independent of body size, AVA was significantly correlated with height, weight, BSA and BMI (Pearson correlation coefficient (r) 0.319, 0.281, 0.317 and 0.126, respectively, all p<0.001) to the effect that larger patients presented with larger AVA (less severe stenosis). Of the anthropometric measures used for linear adjustment, BSA was most effective in eliminating the correlation between AVA and body size (r=0.007), rivalled only by allometric (non-linear) models, findings that are confirmed in 1525 prospectively followed patients from the SEAS study. Predictive accuracy for aortic valve events and cardiovascular death during 46 months of follow-up was unchanged by adjusting AVA, regardless of measure of body size (area under the receiver operating curve for AVA 0.72 (CI 0.58 to 0.87) versus, for example, AVA/BSA 0.75 (CI 0.61 to 0.88), p=0.22).

In the assessment of aortic stenosis, linear adjustment of AVA by BSA improves comparability between patients with diverging body size without, however, increasing the predictive accuracy for clinical events in a population with mild to moderate stenosis.