Prognostic value of stroke volume index after low-dose dobutamine stress testing in asymptomatic patients with severe high-gradient aortic stenosis and normal left ventricular ejection fraction

Background There is limited and conflicting evidence regarding the prognostic significance of indexed left ventricular stroke volume (SVi) in asymptomatic patients with high-gradient severe AS and normal left ventricular ejection fraction (LVEF). However, to our knowledge, the prognostic implications of different SVi values after low dose dobutamine testing (DSE) in asymptomatic patients with high-gradient severe aortic stenosis (AS) and normal LVEF have not been investigated Aim We investigated the prognostic role of left ventricular SVi after low-dose DSE testing in asymptomatic patients with high-gradient severe AS and normal LVEF Methods 121 consecutive asymptomatic patients with severe AS and normal LVEF (≥55%) were included. All patients were ≥ 18 years old. Exclusion criteria were obstructive pulmonary disease, atrioventricular block/bradycardia with a heart rate below 50 beats/min, other significant valvular disease, and uncontrolled hypertension (>180/100 mmHg) Patients were divided into 3 subgroups according to amount of stroke volume flow across the aortic valve: a) SVi > 35 ml/m2, b) SVi 30–35 ml/m2 and SVi < 30ml/m2. After the echocardiographic examination at rest, DSE with small dosages by intravenous dobutamine was done, starting with 5 μg/kg/min, with up to a maximum of 20 μg/kg/min. Clinical data at follow-up were obtained from all patients by direct patient examination or telephone interview. None of the patients have been lost during follow-up. The primary outcome of the study was all-cause mortality. The local ethics committee approved the study, and all patients gave written informed consent. Results The study population included 52 asymptomatic women and 69 asymptomatic men (57% males), mean age was 66 ± 10. The median follow-up was 38 months (IQR 35-42 months). The AS was most often (74%) degenerative in origin. Mean pressure gradient was 42.12 ± 11.37 mmHg, mean AVA 0.84 ± 0.23 cm 2, mean Vmax was 4.21 ±0.50 m/sec, and mean LVEF was 72+ 7%. There was no difference in demographic, clinical and echocardiographic characteristics between the groups according to SVi cut-off values at baseline. As regard to echo-Doppler parameters of AS severity at baseline, patients with SVi < 30mL/m2 had significantly smaller AVA compared to those with 30-35mL/m2 or> 35 ml/m2 (AVA 0.66 vs 0.78 vs 0.90cm2; p<0.05). Patients with SVi < 30ml/m2 after low-dose DSE had significantly lower survival in comparison to patients in other two groups (p=0.025 and p<0.001, respectively) and 13-fold higher mortality in comparison to patients with SVi> 35mL/m2; while there was no difference in survival among patients in two other SVi groups; Figure 1. Conclusion Low flow defined as SVi <30 mL/m2 after DSE is the strongest mortality predictor among asymptomatic patients with high-gradient severe AS and normal LVEFFigure 1:Survival according to DSE SVi