Recurrent valve obstruction in a patient with a pure carbon bileaflet metallic mitral valve: a case report

Despite overcoming the morbidity from severe native valve disease, prosthetic metallic valve replacement is not without its inherent morbidity, in particular from prosthetic valve thrombosis (PVT). The contemporary pure carbon bileaflet metallic valve confers reduced thrombogenicity.

We describe the case of a 45-year-old woman with a pure carbon bileaflet metallic mitral valve replacement (27/29 mm On-X) 6 months previously for severe rheumatic mitral stenosis, who presented with a rapid onset of dyspnoea, paroxysmal nocturnal dyspnoea, and haemoptysis. This was preceded by an interruption in therapeutic anticoagulation. On admission the patient was in cardiogenic shock. Transthoracic and transoesophageal (TOE) echocardiograms revealed increased transmitral gradients with disc hypomobility, suggestive of PVT, unexpected given the favourable safety profile of the On-X valve. Fluoroscopy confirmed the findings. The patient was thrombolysed successfully with alteplase, with restoration of normal transmitral gradients. A target international normalized ratio of 3.5-4.5 was chosen, in addition to aspirin 75 mg, to minimize thrombotic sequalae. Repeat TOE 6 weeks later revealed disc hypomobilty with a large adherent clot. Due to the high risks from thrombolysis, emergency redo-mitral bioprosthetic valve surgery was performed, to negate the need for long-term anticoagulation.

Subtherapeutic anticoagulation and the rapid development of dyspnoea, should prompt the clinician to suspect PVT. Thorough clinical examination and immediate bedside echocardiography are critical for assessing prosthetic valve patients in cardiogenic shock. The treatment of PVT is complex, with considerable risks to the patient, irrespective of the strategy (thrombolysis/emergency valve replacement), necessitating the expertise of cardiologists and cardiac surgeons.