Background—No large prospective studies have evaluated the efficacy of fibrinolytic therapy for left-sided prosthetic valve thrombosis, yet it remains the first line of treatment in developing countries.

Methods and Results—We performed a randomized controlled trial comparing an accelerated infusion with the conventional infusion of streptokinase in 120 patients with a first episode of left-sided prosthetic valve thrombosis. The primary outcome measure was the occurrence of a complete clinical response, defined as objectively documented complete restoration of valve function in the absence of major complications. The secondary outcome was a composite of death, major bleeding, embolic stroke, or non–central nervous system systemic embolism. Patients were recruited over a 2.5-year period at a single center in India. Complete clinical response occurred in 38 (64.4%) of 59 patients with the accelerated infusion compared with 32 (53.3%) of 60 with the conventional infusion (hazard ratio 1.6, 95% confidence interval 0.9 to 2.5, P=0.055). There was no significant difference in the occurrence of the composite secondary outcome (hazard ratio 1.4, 95% confidence interval 0.5 to 3.5, P=0.50) or major bleeding (hazard ratio 2.2, 95% confidence interval 0.6 to 7.7, P=0.24) with the accelerated infusion. The success rate with fibrinolytic therapy was low overall (59%) and very low in patients in New York Heart Association functional class III/IV (24%).

Conclusions—The large number of patients recruited from a single center underscores the massive burden of prosthetic valve thrombosis in developing countries. Fibrinolytic therapy with streptokinase is less efficacious than previously believed. The accelerated streptokinase infusion is not better than the standard infusion for left-sided prosthetic valve thrombosis. Developing countries urgently need more effective strategies to prevent and treat prosthetic valve thrombosis.