Case 9 — Two-Dimensional Echocardiograms

Right parasternal long-axis view showing the left atrium (LA) larger than the left ventricle (LV). A defect is visible in the mitral valve and the leaflet tips flail back into the left atrium. RV — right ventricle; RA — right atrium.
Right parasternal long-axis view. The LA is larger than the LV. A defect in the mitral valve is visible with flailing leaflet tips protruding into the LA. RV; RA.
Right parasternal cross-sectional view of the base of the heart showing the left atrium (LA) markedly enlarged with the left auricle projecting cranially. Normally 2 to 3 aortic (AO) cross-sections fit into the LA; this LA would hold about 9 to 10.
Cross-sectional base view. The LA is markedly enlarged (would hold ~9–10 aortic cross-sections; normal is 2–3). The enlarged left auricle projects cranially.
Left apical four-chamber view showing massive left atrial (LA) enlargement. The mitral valve leaflets do not appose. LV — left ventricle; RV — right ventricle.
Left apical four-chamber view. Massive LA enlargement. The mitral valve leaflets do not appose. LV; RV.
Right parasternal view showing the mitral valve leaflets in cross-section, partially opened during atrial systole leaving a mitral valve orifice (MVO). The leaflet edges are uniformly thickened around the circumference. LVOT — left ventricular outflow tract; RV — right ventricle.
Cross-sectional view of the mitral valve leaflets (atrial systole). The leaflet edges are uniformly thickened. MVO — mitral valve orifice; LVOT; RV.

Video of the mitral valve from another dog with the same disease

The inner 50% of the septal (anterior) leaflet of the mitral valve is markedly thickened. The portion of the leaflet tip protrudes beyond the point where it should coapt with the mural leaflet. This is another example of mitral valve flail. In addition, the diseased portion of the leaflet protrudes backward into the left atrium — an example of severe mitral valve prolapse.

Quiz

1. All of the above findings are consistent with what diagnosis?

2. What is the most likely cause of the mitral valve flail?

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