One of the first things I look for when performing transesophageal echocardiography (TEE) for a mitral valve replacement is how the new valve is functioning as we prepare to separate from cardiopulmonary bypass. A mechanical mitral valve is engineered for crisp, nearly effortless leaflet excursion; however, the following 3D TEE view of a mechanical On-X mitral valve shows a fixed/partially mobile leaflet, which transforms this prosthesis into an acute obstructive lesion analogous to mitral stenosis.
This mechanical failure is rarely due to chronic thrombus in the immediate post-operative window; instead, it is typically caused by extrinsic mechanical impediments such as residual chordal tissue, suture material, air emboli, a defective valve, or even the inversion of the residual native subvalvular apparatus, which interferes with leaflet motion.
The resulting pathophysiology deteriorates rapidly because mitral inflow obstruction acutely elevates left atrial pressure, which is transmitted backward into the pulmonary venous circulation. Despite adequate contractility, the left ventricle becomes underfilled because preload can no longer effectively traverse the obstructed valve, leading to a precipitous drop in cardiac output and a sharp rise in pulmonary artery pressures. On Doppler imaging, this manifests as unexpectedly elevated transmitral gradients and restricted leaflet motion on 2D and fluoroscopic views.
In any case, the surgeon must reinitiate cardiopulmonary bypass and reopen the heart to promptly identify and correct the defect.
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