Unravelling the Diagnosis of Normal-Flow Low-Gradient Aortic Stenosis: The Role of Multimodality Imaging

Normal-flow, low-gradient aortic stenosis is one of the most deceptive presentations of aortic stenosis. It leaves clinicians uncertain whether they are facing true severe disease or a measurement artefact. This often reflects a discordant grading pattern, in which many patients ultimately prove to have moderate disease. This diagnostic paradox arises from a combination of measurement errors, geometric assumptions, and genuine hemodynamic complexity, and cannot be resolved by echocardiography alone. A structured multimodality imaging strategy integrating calcium score evaluation on cardiac computed tomography, tissue characterisation on cardiac magnetic resonance and, when necessary, invasive hemodynamic assessment is the only reliable path to diagnostic certainty and appropriate therapeutic decision-making. Together, these modalities form a coherent sequential algorithm that moves from the non-invasive to the invasive, from the hemodynamic to the biological, and from uncertainty to actionable clinical decision. This review provides an updated, critical appraisal of each imaging tool and its respective strengths and pitfalls.