Thrombosis of mechanical valve prosthesis: thrombolysis vs surgical treatment. Report of two cases, personal experience and review of the literature.

We report the cases of two patients, previously operated for mitral mechanical valve replacement who developed thrombosis of the prosthesis. The two patients were successfully treated with pharmacological thrombolysis with no recurrence. One patient developed late peripheral embolization most probably due to late mobilisation of a thrombotic fragment. Our experience with surgical management is reported (39 mitral and 5 aortic prosthetic thrombosis from 1982 to 1999 among 89 patients with prosthetic malfunction). Average time interval between surgery and thrombus formation is 26 months (max 204, min 1 month). Rate of mitral thrombosis is 3.9% and aortic 0.25%. Clinical presentation spreads from almost asymptomatic patients to critically ill patients with pulmonary oedema or frank cardiogenic shock. Temporary suspension of anticoagulant therapy (83% in our study group) to rule out minor surgery, appears to be the most frequent cause of thrombosis. Transthoracic or better transoesophageal echo-cardiography and Doppler are by far the most accurate diagnostic tools that can entirely replace angiographic assessment. Operative mortality was 64% in the prosthetic mitral thrombosis and 20% in the aortic one. Thrombolytic treatment may be affected by minor to relevant complications such as peripheral or central embolization but in our experience and according to the literature it seems much less hazardous than re-do surgery. Thrombolytic treatment is advocated for critical patients unless emergency institution of cardio pulmonary bypass is required and/or indicated. Re-do surgery remains indicated for all other cases of prosthetic malfunction.