Beyond diameter: emerging imaging biomarkers for risk stratification in thoracic aortic aneurysms

Thoracic aortic aneurysm (TAA) is a relatively common, under-recognised and lethal condition. Yet, current management remains anchored on absolute diameter for prophylactic repair, despite many dissections occurring below surgical thresholds—particularly in women. This review synthesises evidence showing that while rigorous standardisation of imaging is foundational, diameter alone is insufficient for accurate risk prediction. We appraise clinically available biomarkers beyond size: indexed metrics (Aortic Size Index, Aortic Height Index, Indexed Aortic Area) that adjust for body habitus—especially relevant in women; morphological descriptors (ascending length, arch tortuosity, aortic volume) that capture geometry; dynamic and biomechanical measures (growth rate, regional deformation, distensibility/stiffness) that reflect disease activity and advanced modalities (four-dimensional flow MRI, vascular deformation mapping) that quantify haemodynamics such as flow displacement and wall shear stress. Functional aortic markers—including central blood pressure, aortic stiffness, pulsatile arterial load and arterial age—independently predict expansion and improve risk stratification when combined with diameter. Furthermore, recognition of sex differences in TAA growth and outcomes supports sex-informed, precision aortic imaging and functional approaches to risk assessment. Future priorities include prospective multicentre validation, actionable sex-specific thresholds and multidisciplinary collaboration to translate these tools into personalised surveillance and timely intervention.