Indexing aortic valve area by body surface area increases the prevalence of severe aortic stenosis

Background To account for differences in body size in patients with aortic stenosis, aortic valve area (AVA) is divided by body surface area (BSA) to calculate indexed AVA (AVA(index)). Cut-off values for severe stenosis are <1.0cm(2) for AVA and <0.6cm(2)/m(2) for AVA(index). Objective To investigate the influence of indexation on the prevalence of severe aortic stenosis and on the predictive accuracy regarding clinical outcome. Methods Echocardiographic and anthropometric data from a retrospective cohort of 2843 patients with aortic stenosis (jet velocity >2.5m/s) and from 1525 patients prospectively followed in the simvastatin and ezetimibe in aortic stenosis (SEAS) trial were analysed. Results The prevalence of severe stenosis increased with the AVA(index) criterion compared to AVA from 71% to 80% in the retrospective cohort, and from 29% to 44% in SEAS (both p<0.001). Overall, the predictive accuracy for aortic valve events was virtually identical for AVA and AVA(index) in the SEAS population (mean follow-up of 46months; area under the receiver operating characteristic curve: 0.67 (95% CI 0.64 to 0.70) vs 0.68 (CI 0.65 to 0.71) (NS). However, 213 patients additionally categorised as severe by AVA(index) experienced significantly less valve related events than those fulfilling only the AVA criterion (p<0.001). Conclusions Indexing AVA by BSA (AVA(index)) significantly increases the prevalence of patients with criteria for severe stenosis by including patients with a milder degree of the disease without improving the predictive accuracy for aortic valve related events.