Abstract 16436: Low Stroke Volume Index is Associated With a Low Transvalvular Gradient and Predicts Survival in Patients With Severe Aortic Stenosis
Background: A low transvalvular mean gradient (MG) is associated with worse outcomes in patients with severe aortic stenosis (AS) (AVA <1.0cm2), but the factors that impact the MG remain incompletely understood. Both low flow and increased global LV load (valvular and vascular load) have been associated with a low MG, with recent data highlighting the adverse impact of increased valvuloarterial impedance (a measure of global LV load).
Objective: To explore the importance of stroke volume index (SVI) and afterload in determining the transvalvular MG and survival among patients with severe AS.
Methods: Data were prospectively obtained on 168 patients with severe AS (indexed AVA [AVAi] <0.6 cm2/m2). Multivariable linear regression models investigated predictors of MG and SVI. A Cox proportional hazards model explored the association of SVI with all-cause mortality; mean follow-up = 1 year.
Results: Of these patients, 55% had a MG <40 mmHg and 39% had EF <50%. After controlling for AVAi and ejection time, a low SVI was associated with a reduced MG (ß=-1.92 mmHg, p<0.001), whereas vascular afterload variables [systemic vascular resistance (SVR), systemic arterial compliance (SAC), mean arterial pressure (MAP), history of hypertension] were not associated with MG (R2=0.80). However, in a separate model predicting SVI, after controlling for AVAi and variables reflecting LV preload, remodeling, and function, the vascular afterload variables SVR, SAC, and MAP were associated with SVI (p<0.001 for all; R2=0.83). Patients with a low SVI (<31 ml/m2) had reduced 1-year survival vs. normal SVI patients (66% vs. 86%, p=0.006). After adjusting for age, gender, EF <50%, prior infarct and aortic valve replacement, a lower SVI was associated with worse survival (HR 1.05 per 1 ml/m2 decrease in SVI, 95% CI 1.01-1.10, p=0.027); valvuloarterial impedance was not (p=0.31).
Conclusions: In patients with severe AS, increased vascular afterload does not appear to directly influence MG but does so indirectly via its effect on SVI. Low SVI is not only a predictor of a low MG, it is also associated with worse survival independent of EF. Routinely assessing SVI, a simple echocardiographic measurement, in patients with severe AS may assist in the clinical management of these patients.
- © 2011 by American Heart Association, Inc.