Performance of Computed Tomographic Angiography-Based Aortic Valve Area for Assessment of Aortic Stenosis

BackgroundA total of 40% of patients with severe aortic stenosis (AS) have low-gradient AS, raising uncertainty about AS severity. Aortic valve calcification, measured by computed tomography (CT), is guideline-endorsed to aid in such cases. The performance of different CT-derived aortic valve areas (AVAs) is less well studied. Methods and ResultsConsecutive adult patients with presumed moderate and severe AS based on echocardiography (AVA measured by continuity equation on echocardiography <1.5 cm(2)) who underwent cardiac CT were identified retrospectively. AVAs, measured by direct planimetry on CT (AVA(CT)) and by a hybrid approach (AVA measured in a hybrid manner with echocardiography and CT [AVA(Hybrid)]), were measured. Sex-specific aortic valve calcification thresholds (& GE;1200 Agatston units in women and & GE;2000 Agatston units in men) were applied to adjudicate severe or nonsevere AS. A total of 215 patients (38.0% women; mean & PLUSMN;SD age, 78 & PLUSMN;8 years) were included: normal flow, 59.5%; and low flow, 40.5%. Among the different thresholds for AVA(CT) and AVA(Hybrid), diagnostic performance was the best for AVA(CT) <1.2 cm(2) (sensitivity, 85%; specificity, 26%; and accuracy, 72%), with no significant difference by flow status. The percentage of patients with correctly classified AS severity (correctly classified severe AS+correctly classified moderate AS) was as follows; AVA measured by continuity equation on echocardiography <1.0 cm(2), 77%; AVA(CT) <1.2 cm(2), 73%; AVA(CT) <1.0 cm(2), 58%; AVA(Hybrid) <1.2 cm(2), 59%; and AVA(Hybrid) <1.0 cm(2), 45%. AVA(CT) cut points of 1.52 cm(2) for normal flow and 1.56 cm(2) for low flow, provided 95% specificity for excluding severe AS. ConclusionsCT-derived AVAs have poor discrimination for AS severity. Using an AVA(CT) <1.2-cm(2) threshold to define severe AS can produce significant error. Larger AVA(CT) thresholds improve specificity.