COR LOE Recommendation For patients with a thrombosed left-sided mechanical prosthetic heart valve who present with symptoms of valve obstruction, urgent initial treatment with either slow-infusion, low- dose fibrinolytic therapy or emergency surgery Synopsis Patients presenting with a thrombosed mechanical valve require urgent therapy. The 2 options of low- dose, continuous-infusion thrombolytic therapy or emergency surgery are both effective, with the decision to proceed with either one based on multiple clinical factors and local experience and expertise. Recommendation-Specific Supportive Text 1. The decision between surgery and systemic fibrinolysis for symptomatic left-sided mechani- cal valve thrombosis should be individualized (Table 23) after review by the heart valve team, while engaging the patient in a process of shared decision-making and accounting for local experi- ence and expertise. The overall 30-day mortality rate with surgery is 10% to 15%, with a lower mortality rate of <5% in patients with NYHA class I or II symptoms.2,3,7 Recent studies using an echocardiogram-guided, slow-infusion, low-dose fibrinolytic protocol have shown hemodynamic success rates >90%, with embolic event rates <2% and major bleeding rates <2%.13 Systemic fibrinolysis is therefore an acceptable alternative to reoperation in patients at high or prohibitive surgical risk and in patients who have a small thrombus burden, mild HF symptoms (NYHA class I or II), and low bleeding risk. Absence of surgi- cal expertise should be considered in the clinical decision-making process as a factor that favors thrombolytics, whereas recurrent valve thrombo- sis favors a surgical approach (Table 23). 11.7. Bioprosthetic Valve Thrombosis 11.7.1. 