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Clinical Images
Mechanical Mitral Valve Thrombosis
August 2009
Case Presentation. A 75-year-old female presented to our hospital with subacute onset of dyspnea and decreased exercise tolerance. Her past medical history was significant for aortic and mitral stenosis secondary to rheumatic heart disease and double valve replacement with bileaflet mechanical valves (Carbomedics). Although she was taking warfarin, there were concerns about her compliance, and her international normalized ratio (INR) was subtherapeutic on arrival. She had no fever and no symptoms suggestive of endocarditis.
A transesophageal echocardiogram (Figures 1A and B) showed that the mitral prosthesis was well seated, but the posterior disk was not moving. The mean gradient across the valve was 7 mmHg (heart rate 73 bpm) and there was mild-to-moderate transvalvular regurgitation due to incomplete closure of the anterior disk. The aortic valve was functioning well, but there was moderate-to-severe tricuspid regurgitation with a systolic pulmonary artery pressure of 77 mmHg. Given the clinical presentation, a diagnosis of mitral valve thrombosis was made. The patient underwent right and left heart catheterization in anticipation of surgery to replace the mitral valve. Fluoroscopy clearly demonstrated the immobilized posterior leaflet (Figures 2A and B). The patient was taken to surgery for replacement of both her aortic and mitral valves with bioprostheses and for tricuspid annuloplasty. Unfortunately, the patient arrested in the OR and could not be resuscitated successfully. A pathology report confirmed the presence of recent thrombus on the mitral valve.
Prosthetic valve thrombosis has a reported incidence of 0.1–5.7% per patient-year and is more common with valves in the mitral position.1 Factors that increase the risk of thromboembolic complications include atrial fibrillation, previous thromboembolism, a hypercoagulable state and severe left ventricular dysfunction.2 Treatment consists of emergency surgery or fibrinolysis. Surgery is generally preferred for left-sided valves because fibrinolysis carries a 12–15% risk of cerebral embolization. Occasionally, conservative treatment with unfractionated heparin may be considered for patients with mild symptoms and a small clot burden. To minimize the risk of thrombosis, patients with bileaflet mechanical valves should be anticoagulated with a target INR of 2.0–3.0 for aortic valves and 2.5–3.5 for mitral valves.2
From the Division of Cardiology, SMBD Jewish General Hospital, McGill University, Montréal, Québec, Canada.
Address for correspondence: Lawrence Rudski, MD, Jewish General Hospital, Suite E-0079, 3755 Côte Ste. Catherine Road, Montréal, QC, H3T 1E2. E-mail: lrudski@cardio.jgh.mcgill.ca
1. Vongpatanasin W, Hillis LD, Lange RA. Prosthetic heart valves. N Engl J Med 1996;335:407–416.
2. Bonow RO, Carabello BA, Chatterjee K, et al. 2008 Focused update incorporated into the 2006 ACC/AHA guidelines for the management of patients with valvular heart disease. J Am Coll Cardiol 2008; 52:e1–e142.
