Usefulness of 3D Transthoracic Echocardiography to Clarify and Display the Mechanism of Mitral Regurgitation

by Denisa Muraru, MD, PhD 
Department of cardiac, thoracic and vascular sciences, University of Padua, School of Medicine, Padua, Italy

Clinical Case

  • 37-year-old man
  • Active lifestyle, asymtomatic
  • Incidental finding of apical systolic murmur
  • Referred to the echo lab for evaluation of valve function

Two-dimensional PLAX view, showing no signs of mitral prolapse or aortic valve stenosis.

However, by color Doppler, an eccentric, posteriorly directed mitral regurgitation (MR) jet was visualized, suggesting a possible abnormality of the anterior leaflet.

A zoomed MV image was obtained, in which the eccentric MR seemed to be related to a billowing or a small prolapse of anterior MV leaflet. However, additional views of the MV were acquired for clarifying the mechanism of MR.

Two-dimensional PSAX view, with and without color Doppler, confirming the presence of eccentric MR jet with unclear origin.

Two-dimensional 4-chamber view, with and without color Doppler, confirming the presence of a highly eccentric MR with Coada effect, oriented towards the postero-lateral left atrial wall. No evident prolapse is seen in this view.

Two-dimensional 2-chamber view, with color Doppler imaging, in which a flow convergence is seen in the proximity of basal inferior wall (with routine velocity settings), suggesting a significant MR due to P3 lesion.

Two-dimensional apical long-axis view, confirming the posteriorly directed MR jet.

Two-dimensional apical long-axis view (zoomed MV image), showing an “abnormality” of the anterior leaflet, in systole, on its atrial aspect, suggesting either a prolapse in a different plane or (less probable) a vegetation.

Since the mechanism of MR was still unclear after performing a standard 2D echo study of the MV, a 6-beat 3D dataset of the LV (including the MV) was acquired from the apical approach for 2 purposes: 1. MV reconstruction; 2. LV quantification.

Three-dimensional rendering of the MV in the “surgical view” (aortic valve, AV at 12 o’clock; left atrial appendage, LAA at 9 o’clock) showing a prolapse seen as a systolic bulging pf the medial commissure (*) and P3.

The dataset is rotated counterclockwise so the prolapse of the medial commissure (*) and P3 is easily appreciated.

If still unsure about the presence and localization of the prolapse from the surgical view (in which small prolapses are more difficult to identify by less experienced readers), one trick is to use the “parallel cropping” mode which eliminates the irrelevant structures from the far field and enhances the color gradient of the LV rendering, so that closer structures, i.e. prolapsing segment is colored differently (bronze) than the rest of the valve (blue, since it lies at a deeper level).

Simple cropping – using one cropping plane (red line) in the left atrium, close to the MV. Arrow shows the viewing perspective.

Parallel cropping – using one cropping plane in the left atrium, close to the MV; and an additional one in the LV. All the structures outside the two “parallel” cropping planes are removed. Note the bluish color of the MV leaflets with respect to the simple cropping, making the identification of the prolapse much easier.

The use of “Flexi-slice” tool can be used to confirm the presence and localization of MV prolapse, by its ability to display side-by-side the 3D rendered, the 2D slice and the longitudinal cutplanes corresponding to the lines that intersect the 3D rendered image. Prolapsing segment is shown by the yellow arrow.

Finally, switching back to 2D modality and performing an unconventional 2-chamber view focused on the P3 segment, shows the clear presence of a prolapse and the loss of coaptation (still frame, arrow).

The LV quantitative analysis showed a mildly dilated LV (3D EDV=87 ml/m2) with normal EF (65%). Doppler criteria were supportive of moderate-severe MR. The patient was confirmed to be asymptomatic at exercise echo and close follow-up was recommended.

Key Messages

2D echocardiography:

  • The mechanism of the MR and the exact localization of the prolapse can be uncertain from standard 2D views and from interpreting the MR jet direction, especially when the prolapse spares the A2 and P2 segments and involves a commissure (i.e. unpredictable jet direction).

3D echocardiography:

  • Provided a clear visualization of the presence, localization and extension of the prolapse.
  • Provided reliable quantitative information on LV volumes and ejection fraction.
  • In case of small prolapses, difficult to read from the conventional 3D “surgical view”, the use of additional cropping tools (parallel cropping, Flexi-slice etc) and the focused re-evaluation from unconventional 2D views can be used for confirmation.
  • The identification of P3-commissural lesion suggests a more difficult surgical repair, that, in the presence of clinical indication, needs to be performed in a high-volume, expert center in MV repair.

References

  1. Lang RM, Badano LP, Tsang W et al. EAE/ASE Recommendations for Image Acquisition and Display Using Three-Dimensional Echocardiography. Eur Heart J Cardiovasc Imaging 2012; 13:1-46
  2. Muraru D, Cattarina M, Boccalini F et al. Mitral valve anatomy and function: news insights from three-dimensional echocardiography. J Cardiovasc Med. 2013; 14-2:91-9