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Echocardiography and 4D flow MRI

Echocardiography and 4D flow MRI

We are investigating a hemodynamic characteristics of diseased heart valves using two representative non-invasive flow analysis technique, echocardiography and 4D flow MRI. By exploiting the complementary advantages of both techniques, our same-day echo and 4D flow MRI studies have shed new light on shortcomings surrounding the assumptions used for valve disease assessment. Specifically, studies of the left ventricular outflow tract (LVOT) and aortic transvalvular flow showed that 3D velocity measurements with 4D flow MRI allow for accurate computation of the volumetric flow rate and localization of the vena contracta, which can be challenging in multiple and/or eccentric jets. However, the lower temporal and spatial resolution of 4D flow MRI compared to echocardiography leads to underestimation of faster flow.

We use a continuity equation to estimate the effective orifice area of stenotic aortic valves. (a). Here, echocardiography assumes circular left ventricular outflow tract and flat velocity profile (b), while 4D flow can measure the periphery area of the LVOT area and compute actual velocity profile (c).

a) LVOT peak velocity, b) Aorta peak velocity and c) EOA measured by echo and 4D flow MRI was compared in Bland Altman plots. 4D flow MRI can localize peak velocities in LVOT and aorta better than echocardiography, but limited spatio-temporal resolution underestimates fast flows found in aortic stenosis patients.

Investigators: Hyungkyu Huh (PhD), Menhel Kinno (MD), James D Thomas (MD), Alex Barker (PhD), Michael Markl (PhD)

Publications and presentations:

  • Huh HK, Kinno M, Thomas JD, Markl M, Barker AJ. Estimation of aortic valve effective orifice area: a same day comparison between Doppler echocardiography and 4D flow MRI. International Society for Magnetic Resonance in Medicine (ISMRM) Annual Meeting (2018) Paris, France
  • Huh HK, Barker AJ, Kinno M, Markl M, Thomas JD. Sometimes two wrongs DO make a right: Opposite effects of errors in LVOT area and mean velocity estimation largely cancel out when calculating stroke volume. American Society of Echocardiography (ASE) Annual Scientific Sessions (2018) Tennessee, USA
  • Huh HK, Kinno M, Thomas JD, Markl M, Barker AJ. Peak velocity across the aortic valve using same-day Doppler echocardiography and 4D flow MRI. Society for Magnetic Resonance Angiography (SMRA) Annual Meeting (2018) Glasgow, Scotland