The accurate assessment of the haemodynamic severity of stenosis is crucial for clinical decision making in patients with aortic stenosis (AS).¹ Over the past decades, echocardiography has become the clinical standard for the evaluation of AS severity. Several indices have been used for this purpose including transvalvular velocity and gradient, aortic valve area (AVA), valvular resistance, dimensionless velocity index, left ventricular (LV) stroke work loss and the energy loss coefficient. Unfortunately, these indices are all potentially affected by the haemodynamic state of the patient. Numerous studies have shown that changes in transvalvular flow rate may influence the indices of stenosis severity measured by echocardiography or catheter.^2–4 Besides flow rate, there are potentially other haemodynamic factors that may affect the stenotic indices. The purpose of the study by Little et al⁵ (see page 848) reported in this issue of Heart was to examine the effects of systemic arterial hypertension on the Doppler-echocardiographic indices of stenosis severity. This study is of high clinical relevance, since AS and hypertension are the two most frequent cardiovascular diseases after coronary artery disease in the Western world, and 30–40% of patients with AS concomitantly have hypertension.^6,7 Several authors have previously reported that the transvalvular gradient may be reduced in patients with concomitant systemic hypertension.^8,9,10 It was, however, unclear in these reports: (1) whether this phenomenon was systematic or not; (2) whether it was predictable or not; and (3) whether it was due to a direct effect of increased systemic vascular resistance and/or reduced arterial compliance on the transvalvular gradient, or due to an indirect effect associated with a concomitant reduction in flow rate. The interaction between valvular and arterial haemodynamics therefore needs to be better understood to improve the evaluation of AS severity …