Abstract 20173: Mechanism Of Low Transvalvular Aortic Stenosis : Geometry, Resistance, and Function
Background: There exists a discrepancy between the degree of severity based on mean transvalvular gradients (mPG) and the stenotic valve area (AVA) calculated by the continuity equation in severe aortic stenosis (sAS). The aim of this study is to clarify the mechanism of low gradient sAS.
Methods and Result: We retrospectively studied two-dimensional and Doppler echocardiography data of 134 consecutive patients with severe AS (AVA <1.0cm2) and preserved left ventricular ejection fraction (LVEF) (>50%) in order to assess properties of circulation, valve, ventricular function and geometry. Of these patients,72 (53%) had high gradients defined as mPG >30mmHg (HG group) and 62 (47%) had low gradients. (LG group) (mPG<30mmHg) The values of arterial systolic blood pressure were similar in two groups, although the mean systemic blood pressure and the systemic arterial resistance was markedly higher in LG group. The AVA and the valvular resistance were significantly higher in HG group, which suggests the stenosis is in fact more severe in HG group than that in LG group. Table shows the comparison of indices of LV geometry and function. Overall, HG and LG patients generally had concentric LV hypertrophy or remodeling. The LV mass index and the relative wall thickness were much higher in HG group, which suggests LV remodeling/hypertrophy may be due to valvular resistance. Compared with HG group, stroke volume, cardiac output and mean transvalvular flow rate were lower in LG group, and flow acceleration time(AT) and AT to ejection time ratio were markedly lower in LG group, which implies impaired ejection dynamics in LG group may be related to increased net afterload e.g. high valvulo-arterial impedance and net resistance (valve resistance+vascular resistance).
Conculusion: HG group had more severe valve stenosis as compared to LG group in which global LV load is more pronounced leading to impaired ejection dynamics and resultant low flow, low pressure gradient state.
- © 2010 by American Heart Association, Inc.