BackgroundAortic valve area (AVA) using CT-LVOT area (AVACT-LVOT) <1.2 cm2 has been shown comparable to echocardiography AVA of <1.0 cm2 for severe aortic stenosis (AS). Current study evaluates how AS diagnosis will be affected when we substitute CT-LVOT with echo derived LVOT. MethodsWe retrospectively studied 367 patients who underwent cardiac CTA and echocardiogram for assessment of high- and low-gradient AS (HG-AS and LG-AS). AVACT-LVOT was derived from CT-LVOT area and echo doppler data. Three AVACT-LVOT categories were created (<1.0, 1.0–1.2 and > 1.2 cm2). Outcomes were defined as composite of all-cause mortality and/or valve intervention. ResultsMedian echocardiographic profiles were consistent with severe AS across three AVACT-LVOT categories for HG-AS. HG-AS patients with AVACT-LVOT >1.2 cm2 had larger median CT-LVOT area (5.06 cm2) and AVC (2917AU). Among LG-AS with AVACT-LVOT ≤1.2 cm2, 57% met echo criteria for low-flow LG-AS and 63% met criteria for severe AS using aortic valve calcium (AVC). Additionally, 45% with AVACT-LVOT >1.2 cm2 had larger median CT-LVOT area (5.43 cm2) and AVC (2389AU). Patients with AVACT-LVOT >1.2 cm2 and high AVC had large body surface area and were mostly characterized as severe with indexed AVA and AVC. Stroke volume index using CT-LVOT reclassified 70% of low-flow, LG-AS as normal flow, LG-AS. Composite outcomes were higher among patients with AVACT-LVOT ≤1.2 cm2 (p < 0.01), however, with no superior net reclassification improvement compared to AVAecho <1.0 cm2. ConclusionAVACT-LVOT ≤1.2 cm2 is a reasonable CT criterion for severe AS. Large LVOT with elevated AVC identified a severe AS phenotype despite an AVACT-LVOT >1.2 cm2, best characterized by indexed AVA and AVC.