Prosthetic valve thrombosis in pregnancy: a promising treatment for a rare and mostly preventable complication.

P rosthetic heart valve thrombosis (PVT) is a rare complication , with an estimated incidence of 0.1% to 5.7% per patient-year. 1 However, during pregnancy, changes in the hemostatic system lead to a procoagulant state that increases the risk of PVT up to 10%. 2 This maternal and fetal life-threatening complication is mostly preventable with long-term adequate anticoagulation therapy. When anticoagulation fails, treatment focuses on choosing between cardiac surgery and thrombolysis, 2 therapeutic strategies with risks and benefits for the mother and fetus that are difficult to assess. The study by Özkan et al 3 in this issue of Circulation is the largest series of pregnant patients with prosthetic mitral valve thrombosis reported to date and offers interesting results in a scenario in which randomized, clinical trials are not feasible. A protocol of low-dose, slow infusion of tissue-type plasmin-ogen activator with repeated doses as needed that was guided by transesophageal echocardiography was associated with a successful thrombolysis in all episodes, with no maternal deaths and a fetal mortality rate of 20%, results that seem to be better than those obtained with other thrombolytic strategies reported. The authors' conclusions on the superiority of thromboly-sis over surgery and the redefinition of the lytic option as a first-line therapy in pregnant patients with PVT require careful evaluation. Previous studies of cardiac surgery showing maternal and fetal mortality rates of 6% and 30%, respectively, were published a decade ago and were based mostly on coronary revascularization procedures. Since then, some recommendations have been included, such as appointing the procedure during the second trimester of pregnancy when possible, monitoring intraoperative fetal heart rate and uterine contractions, and maintaining normothermia during the surgery. In fact, results of more recent series of surgical management of val-vular diseases in pregnant women seem to have improved. It is noteworthy that 4 of the 28 events were rethrombosis; 3 of them were recurrent obstructive thrombi occurring during the same pregnancy. The intervals between the first PVT treated with thrombolysis and the recurrence were 3, 6, and 10 weeks; the doses of tissue-type plasminogen activator used in the first event ranged from 25 to 100 mg. These observations raise the question of whether the first treatment should be considered indeed successful or whether the definition of thrombolytic success should include some time free of thrombosis besides the echocardiography and clinical criteria. However, an adequate anticoagulant treatment after thrombolysis is essential to …