Impact of low stroke volume on mortality in patients with severe aortic stenosis and preserved left ventricular ejection fraction

In patients with severe aortic stenosis (AS) and preserved left ventricular ejection fraction (LVEF), low flow (LF) is currently defined using Doppler-echocardiography by a stroke volume index (SVi)<35 mL/m². However, the relationship between LF and outcome remains unclear as data on normal reference values defining LF are scarce, and previous studies did not explore the risk associated with other SVi cut-points. We analysed the relationship between LF and mortality in severe AS to establish prognostic LF values associated with mortality risk.

This study included 1450 consecutive patients with severe AS (aortic valve area <1 cm² and/or <0.6 cm²/m²) and preserved LVEF and 1645 controls with normal echocardiograms. Patients were stratified in three groups: (i) SVi > 35 mL/m² or SV > 70 mL; (ii) SVi 30–35 mL/m² or SV 55–70 mL; and (iii) SVi < 30 mL/m² or SV < 55 mL. Mortality with medical and surgical management was analysed. Five-year survival was low for SVi < 30 mL/m² and SV < 55 mL compared to the other groups (all P-values <0.001). After adjustment for outcome predictors, including aortic valve replacement, mortality risk was considerable with SVi < 30 mL/m² vs. >35 mL/m² [adjusted hazard ratio (HR) 1.60 (1.17–2.18)] and SV < 55 mL vs. >70 mL [adjusted HR 1.84 (1.32–2.58)]. Similar mortality risk was observed for SVi 30–35 mL/m² vs. >35 mL/m² [adjusted HR 1.05 (0.78–1.41)], and for SV 55–70 mL vs. >70 mL [adjusted HR 1.22 (0.94–1.58)]. The prognostic impact of SVi < 30 mL/m² and SV < 55 mL was consistent in subgroups, including asymptomatic patients and patients with low-gradient severe AS.

Low flow defined as SVi < 30 mL/m² or SV < 55 mL is an important outcome predictor in severe AS with preserved LVEF under medical and surgical management. Further studies are needed to prospectively test these values for risk stratification and decision making.