Outcome Implication of Aortic Valve Area Normalized to Body Size in Asymptomatic Aortic Stenosis

Abstract

Background: Current guidelines define severe aortic stenosis in patients with aortic valve area normalized to body surface area (AVA/BSA) <0.6 cm²/m²; yet, this cutoff has never been validated. Moreover, it is not known whether AVA normalization to other body size indexes allows improved outcome prediction. We aim to test the value of AVA normalized to body size for outcome prediction in asymptomatic aortic stenosis.

Methods and results: We included 289 patients with asymptomatic aortic stenosis, preserved ejection fraction, and AVA<1.3 cm² at diagnosis. The outcome measure was the occurrence of aortic valve replacement or all-cause death or during follow-up. AVA was normalized to BSA, height, weight, and body mass index. For each normalized index, patients in the lowest tertile were at high risk of events whereas outcome was similar for the other tertiles. High risk of events was observed with AVA/BSA <0.4 cm²/m² (adjusted hazard ratio [HR], 3.42 [2.09-5.60]), AVA/height <0.45 cm²/m (adjusted HR, 3.99 [2.42-6.60]), AVA/weight <0.01 cm²/kg (adjusted HR, 3.37 [2.07-5.49]), and AVA/body mass index <0.029 cm²/kg per meter square (adjusted HR, 3.23 [1.99-5.24]). Mortality risk was high with AVA/height <0.45 cm²/m (adjusted HR, 2.18 [1.28-3.71]), followed by AVA/BSA <0.40 cm²/m² (adjusted HR, 1.84 [1.09-3.11]), AVA/weight <0.01 cm²/kg (adjusted HR, 1.78 [1.07-2.98]), and AVA/body mass index <0.029 cm²/kg per meter square (adjusted HR, 1.75 [1.04-2.93]). AVA/height showed better predictive performance than AVA/BSA with improved reclassification and better discrimination (net reclassification improvement: 0.33 versus 0.28; integrated discrimination improvement: 0.10 versus 0.08; C statistic: 0.67 versus 0.65), whereas AVA/weight and AVA/body mass index showed lower predictive capacity.

Conclusions: Among AVA normalization methods, AVA/height <0.45 cm²/m followed by AVA/BSA <0.40 cm²/m² seem as robust parameters for defining high risk in asymptomatic aortic stenosis. The prognostic value of AVA/height deserves future research.

Keywords: aortic valve; aortic valve stenosis; asymptomatic conditions; echocardiography; prognosis.