Multimodality assessment of high- vs. low-gradient aortic stenosis using echocardiography and cardiac CT

Background: Aortic valve area (AVA) using CT-LVOT area (AVA_CT-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.

Methods: We retrospectively studied 367 patients who underwent cardiac CTA and echocardiogram for assessment of high- and low-gradient AS (HG-AS and LG-AS). AVA_CT-LVOT was derived from CT-LVOT area and echo doppler data. Three AVA_CT-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.

Results: Median echocardiographic profiles were consistent with severe AS across three AVA_CT-LVOT categories for HG-AS. HG-AS patients with AVA_CT-LVOT >1.2 ​cm² had larger median CT-LVOT area (5.06 ​cm²) and AVC (2917AU). Among LG-AS with AVA_CT-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 AVA_CT-LVOT >1.2 ​cm² had larger median CT-LVOT area (5.43 ​cm²) and AVC (2389AU). Patients with AVA_CT-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 AVA_CT-LVOT ≤1.2 ​cm² (p ​< ​0.01), however, with no superior net reclassification improvement compared to AVA_echo <1.0 ​cm².

Conclusion: AVA_CT-LVOT ≤1.2 ​cm² is a reasonable CT criterion for severe AS. Large LVOT with elevated AVC identified a severe AS phenotype despite an AVA_CT-LVOT >1.2 ​cm², best characterized by indexed AVA and AVC.