• Aortic Valve Stenosis
• Tomography, Emission-Computed, Single-Photon

Over the last two decades, the differentiation of severe from non-severe aortic valve stenosis with echocardiography has become more complex. The consideration of flow is now frequently essential to evaluate haemodynamic stenosis severity. Low flow can result in low gradient and, thereby, mask severe aortic stenosis. On the other hand, low flow may impede complete opening of the valve and result in overestimation of the severity by aortic valve area (AVA). Since echocardiographic assessment of flow incorporates parameters which are also used to quantify gradient and AVA, measurement errors may lead to major misclassifications of the disease. This has stimulated the search for a method evaluating stenosis severity by morphological criteria independent of haemodynamics. European Society of Cardiology/European Association for Cardio-Thoracic Surgery Guidelines for the management of valvular heart disease 2021 recommend quantification of valve calcification by CT for assessing the severity of aortic stenosis in patients with low gradient. Aortic valve calcification is measured in (arbitrary) Agatston units (AU), and the diagnosis of severe aortic stenosis considered likely with values >2000 in men and >1200 in women. In the two main studies in this field,1 2 areas under the curve (AUCs) from receiver operating characteristic (ROC) for the diagnosis of severe aortic stenosis compared with echocardiography were …