Adjusting Parameters of Aortic Valve Stenosis Severity by Body Size
In patients with aortic stenosis (AS), does adjusting aortic valve area (AVA) for body size improve identification of patients at risk of clinical events?
This study included 2,843 consecutive patients with AS and normal left ventricular (LV) function retrospectively collected from a single center, and 1,525 patients with asymptomatic mild to moderate AS prospectively evaluated as part of the SEAS (Simvastatin and Ezetimibe in Aortic Stenosis) study. Markers of AS severity were compared to measures of body size (height, weight, body surface area [BSA], and body mass index) in the retrospective cohort, and were compared to size and valvular outcomes (AV replacement, n = 431; heart failure due to AV disease, n = 21; or cardiovascular death, n = 43) in subjects from the second cohort.
In the retrospective cohort, there was no relationship between body size and AV peak velocity, LV outflow tract (LVOT) peak velocity, or AV mean pressure gradient. However, there was a positive relationship between LVOT diameter and all measures of body size (r = 0.13-0.48, p < 0.01). AVA by the Continuity equation was positively associated with body size, attributable to the difference in LVOT diameter, with the strongest relationship observed based on height and BSA (r = 0.32 for each). Linear adjustment of AVA using BSA was superior to adjustment for other body size measures, with a correlation of AVA/BSA to AVA of 0.007. Among the prospective cohort of patients with mild to moderate asymptomatic AS (mean follow-up 46 ± 14 months), the predictive accuracy for aortic valve events was similar for AVA and AVA adjusted for each of the body size parameters. The AUC for AVA to identify aortic valve events was 0.72, which was not significantly improved by adjusting for BSA (AUC 0.75, p = 0.38).
Indexing AVA with BSA removes differences between patients with different body sizes, although it does not improve our ability to identify patients at increased risk of valvular events.
This study demonstrates that there is no significant linear relationship between body size and Doppler measurements including the AV mean gradient, AV peak velocity, or LVOT peak velocity. However, larger patients have larger LVOT diameters, resulting in a positive relationship between body size and calculated AVA. Indexing AVA with BSA is a simple and effective method of accounting for body size, although it does not appear to improve our ability to identify patients at increased risk of events. It is notable that the prospective portion of the study consisted of patients with mild to moderate asymptomatic AS with an intermediate follow-up duration, and that events consisted largely of valve replacement. Further study examining symptomatic patients with moderate and severe AS may be useful to better define the clinical role of AVA indexed to BSA.
Keywords: Body Surface Area, Body Mass Index, Area Under Curve, Ventricular Function, Left, Azetidines, Heart Failure, Aortic Valve Stenosis, Body Size, Simvastatin
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