Paradoxical low-flow (LF) severe aortic stenosis (AS) despite preserved left ventricular (LV) ejection fraction (LVEF) has been shown to be distinct from normal-flow (NF) AS, with a poorer prognosis. Relative valve load (RVL) is a novel echocardiographic haemodynamic index based on the ratio of transaortic mean pressure gradient to the global valvulo-arterial impedance (Zva) in order to estimate the contribution of the valvular afterload to the global LV load. We aimed to determine the usefulness of RVL in LF AS versus NF AS.

A total of 450 consecutive patients with medically managed severe AS (aortic valve area <1.0 cm²) with preserved LVEF (>50%) were studied. Patients were divided into LF (stroke volume index <35 mL/m²) or NF, and high RVL or low RVL. Baseline clinical and echocardiographic profiles, as well as clinical outcomes, were compared.

There were 149 (33.1%) patients with LF. Despite higher global impedance in LF (Zva 6.3±2.4 vs 3.9±0.9 mmHg/mL/m²; p<0.001) compared with NF, the RVL in LF AS was significantly lower (5.4±2.7 vs 9.8±5.1 mL/m²; p<0.001). On multivariable analysis, low RVL (≤7.51) remained independently associated with poor clinical outcomes on Cox regression (hazard ratio, 1.31; 95% confidence interval, 1.03–1.68), with 53.2% sensitivity and 70.3% specificity. This was comparable to other prognostic indices in AS. Kaplan–Meier curves demonstrated that low RVL was associated with increased mortality.

Increased systemic arterial afterload may be important in the pathophysiology of LF AS. Low RVL was an independent predictor of poor clinical outcomes in medically managed severe AS. There may be a greater role in the attenuation of systemic arterial afterload in AS to improve outcomes.