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Unicuspid Aortic Valve: Eccentricity And Non-invasive Pressure Drop In A Single Case
Harminder Singh Gill1, Joao Felipe Fernandes1, Alessandro Faraci1, David Nordsletten1, Ronak Rajani2, Pablo Lamata1.
1King's College London, London, United Kingdom, 2Guy's and St. Thomas's Hospital, London, United Kingdom.

OBJECTIVE: Aortic stenosis (AS) assessment from unidimensional echocardiographic data can yield discrepant metrics of severity with poor symptomatic correlation. Patients with eccentric blood flow and aortic dilatation are susceptible to these shortcomings. Enhanced visualisation of blood flow alongside improved transvalvular pressure drop estimation has been described using 4D-flow MRI. Here we demonstrate the utility of the technique in unicuspid aortic valve anatomy.
METHODS: An asymptomatic 32-year old female under echocardiographic surveillance for a functionally unicuspid aortic valve and aortic dilatation gave informed, written consent to participate in an ethically approved research study (HRA IRAS 262659). The patient underwent routine transthoracic echocardiography (TTE). Cardiac MRI was undertaken on a 3T Philips Scanner with an ECG-gated, respiratory motion-corrected 4D flow MRI sequence. Indices of AS severity were quantified by conventional means using Doppler-TTE. The 4D-flow MRI derived velocity fields were analysed to yield the peak aortic velocity and peak and mean pressure drop accounting for the full velocity profile using Simplified Advective Work (SAW). The EOA was calculated from the continuity equation for both techniques.
RESULTS: From TTE assessment the metrics were consistent with severe aortic stenosis (see table 1). 4D-flow MRI showed peak eccentricity was 62 degrees (figure 1) but the severity of disease would be classified as mild based on peak pressure drop and EOA.
CONCLUSIONS: By incorporating the complete velocity profile the grading of AS is more consistent with the patients symptomatic status. This suggests the technique may be of value in patients with eccentric aortic flow or aortic dilatation where the tendency of Doppler derived metrics to overestimate severity of obstruction may be exacerbated.

Aortic Stenosis Severity Metrics from Doppler Echocardiography and 4D Flow MRI
TechniquePeak Velocity/ m/sPeak Pressure Drop /mmHg (calculated by SB for TTE and SAW for 4D flow MRI)Mean Pressure Drop/mmHg (calculated by SB for TTE and SAW for 4D flow MRI)Effective Orifice Area/ cm2
Doppler Echocardiography4.269420.96
4D-Flow MRI4.535202.9


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