A Diagnostic Pitfall of CT Calcium Scoring in Paradoxical Low-Flow, Low-Gradient Severe Aortic Stenosis With Rheumatic Morphology: a case report

Abstract Background Computed tomography (CT) calcium scoring is used to adjudicate paradoxical low-flow, low-gradient (LFLG) severe aortic stenosis (AS). However, its reliability may be limited in rheumatic disease. Case summary An 82-year-old woman with prior mitral valve replacement for rheumatic mitral stenosis was referred for AS. Transthoracic echocardiography revealed an aortic valve area (AVA) of 0.50 cm2, mean pressure gradient of 27 mmHg, stroke volume index of 30 mL/m2, and preserved systolic function, suggesting paradoxical LFLG severe AS. The CT calcium score was 889 Agatston units, below the female threshold for severe AS. Three-dimensional transesophageal echocardiography (TEE) demonstrated commissural fusion, leaflet tip thickening, and planimetry-derived AVA of 0.69 cm2, confirming severe AS. The patient underwent transcatheter aortic valve implantation, with 6-minute walk distance improving from 150 to 254 m. Discussion In rheumatic morphology, low CT calcium burden may not exclude severe AS because obstruction may be driven by commissural fusion and fibrosis rather than bulky calcification. Three-dimensional TEE planimetry can serve as an anatomy-based adjudicator when echocardiographic and CT calcium findings are discordant.