Relation Between Stroke Volume Index to Risk of Death in Patients With Low-Gradient Severe Aortic Stenosis and Preserved Left Ventricular Function

The aim of the present study was to evaluate whether assessment of stroke volume index (SVI) can be used to improve risk stratification among patients with low-gradient severe aortic stenosis and preserved ejection fraction (EF). Study population comprised 409 patients with aortic valve area ≤1.00 cm2, mean gradient <40 mm Hg, and a normal EF (≥50%) who were followed up in a tertiary referral center from 2004 to 2012. Echocardiographic parameters and clinical data were collected. Multivariate Cox proportional hazards regression modeling was used to evaluate the association between SVI and the risk of all-cause mortality. Mean age of study patients was 78 ± 11 years, and 42% were men. The mean SVI was 39 ± 7 ml/m2 (tertile 1 = 32 ± 4 ml/m2; tertile 2 = 39 ± 1 ml/m2; tertile 3 = 47 ± 4 ml/m2). Multivariate analysis showed that the SVI was the most powerful echocardiographic parameter associated with long-term outcome: each 5 ml/m2 reduction in SVI was associated with a 20% increase in adjusted mortality risk (p = 0.01). Consistently, Kaplan-Meier analysis showed that the cumulative probability of survival during 3 years of follow-up was 60%, 72%, and 73% among patients in the low-, intermediate-, and high-SVI groups, respectively (p = 0.012). Our findings suggest that in patients with low-gradient severe aortic stenosis and preserved EF, there is a graded inverse relation between SVI and the risk of long-term mortality.