Body Surface Area and Prevalence of Severe Aortic Stenosis
Body Surface Area and 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 (AVAindex). Cut-off values for severe stenosis are <1.0 cm for AVA and <0.6 cm/m for AVAindex.
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 >2.5 m/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 AVAindex 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 AVAindex in the SEAS population (mean follow-up of 46 months; 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 AVAindex experienced significantly less valve related events than those fulfilling only the AVA criterion (p<0.001).
Conclusions Indexing AVA by BSA (AVAindex) 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.
Indexing aortic valve area (AVA) by body surface area (BSA) (AVAindex) represents an intuitively convincing and widely adopted method to adjust for differences in body size. Whereas current American College of Cardiology/American Heart Association guidelines on valvular heart disease recommend indexing AVA for all patients, the recently published European Society of Cardiology (ESC) guidelines state that indexing 'may be helpful, particularly in patients with an unusually small BSA'. In the European Association of Echocardiography/American Society of Echocardiography recommendations for clinical practice, the role of indexing is considered controversial particularly because of the uncertain role of excess body weight.
Cut-off values for severe stenosis were set in all guidelines at <1.0 cm for AVA and <0.6 cm/m for AVAindex. However, clinical or outcome studies supporting this recommendation are rare. In theory, calculation of AVAindex should not change the overall number of patients with severe stenosis in a given population but rather result in a decrease in the percentage of patients with the diagnosis of severe stenosis in smaller patients and an increase in larger patients. Based on the hypothesis that adjusting AVA by BSA, that is, AVAindex, improves the comparability of stenosis severity in patients with diverging body size we investigated the impact of AVAindex on the prevalence of severe aortic stenosis and the prediction of clinical events compared to (unindexed) AVA in two large populations of patients with aortic valve stenosis and normal left ventricular function.
Abstract and Introduction
Abstract
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 (AVAindex). Cut-off values for severe stenosis are <1.0 cm for AVA and <0.6 cm/m for AVAindex.
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 >2.5 m/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 AVAindex 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 AVAindex in the SEAS population (mean follow-up of 46 months; 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 AVAindex experienced significantly less valve related events than those fulfilling only the AVA criterion (p<0.001).
Conclusions Indexing AVA by BSA (AVAindex) 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.
Introduction
Indexing aortic valve area (AVA) by body surface area (BSA) (AVAindex) represents an intuitively convincing and widely adopted method to adjust for differences in body size. Whereas current American College of Cardiology/American Heart Association guidelines on valvular heart disease recommend indexing AVA for all patients, the recently published European Society of Cardiology (ESC) guidelines state that indexing 'may be helpful, particularly in patients with an unusually small BSA'. In the European Association of Echocardiography/American Society of Echocardiography recommendations for clinical practice, the role of indexing is considered controversial particularly because of the uncertain role of excess body weight.
Cut-off values for severe stenosis were set in all guidelines at <1.0 cm for AVA and <0.6 cm/m for AVAindex. However, clinical or outcome studies supporting this recommendation are rare. In theory, calculation of AVAindex should not change the overall number of patients with severe stenosis in a given population but rather result in a decrease in the percentage of patients with the diagnosis of severe stenosis in smaller patients and an increase in larger patients. Based on the hypothesis that adjusting AVA by BSA, that is, AVAindex, improves the comparability of stenosis severity in patients with diverging body size we investigated the impact of AVAindex on the prevalence of severe aortic stenosis and the prediction of clinical events compared to (unindexed) AVA in two large populations of patients with aortic valve stenosis and normal left ventricular function.
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