aortic valve area (AVA) calculated by the continuity equation by echocardiography (CE-TTE) is the method of reference to assess aortic valve stenosis severity (AS). The Hakki’s formula (simplified Gorlin formula) is another method, sometines used during cardiac catheterization to calculate AVA. It can also be adapted to magnetic resonance imaging (CMR) to assess the AVA as previously demonstrated. The aim of our study is to investigate, using a large number of patients with AS, the accuracy of the « hakki-cmr » method to determine the severity of AS compared to C-TTE.

between 2007 and 2014, 390 consecutive patients with AS (mean age 81±10 years, men 55%, mean LVEF=60±13%, underwent clinically indicated TTE (IE 33, philips) and CMR (philips ACHIEVA 1.5 tesla) within 30 days. The mean pressure aortic gradient was 44±18mmHg; the AVA was respectively 0.67±0.25cm ² by CE-TTE, 0.74±0.30cm ² using HakkiCMR. Hakki’s formula and AVA from CE-TTE were almost interchangeable, with a mean difference of 0.07cm² (95% limits of agreement 0.15 to 0.21cm², p<0,0001). The intraobserver reproducibility of the AVA measurements with Hakki-CMR was excellent, with an average of 2 measurements of 0.67±0.18 and 0.67±0.13cm ² (intraclass correlation coefficient 0.77, estimated withinsubject SD 0.01cm²).

in a large cohort of patients with AS, assessment of AVA using the Hakki’s formula by CMR, yielded more reliable results than those obtained using planimetry by CMR, and similar to those obtained using the CE-TTE. Despite the potential time and cost issue of CMR, the Hakki formula used during flow quantification, is a valuable method that is reliable easy, and fast to apply. It may be highly useful especially in cases of echogenicity issues by TTE and regardless of the valve degree of calcification.