A 61-year-old woman came to the Emergency Department of our Hospital for fatigue and breathlessness. She was discharged from the surgery ward 2 days before, after a subtotal colectomy for adenocarcinoma had been performed 10 days before. While explaining her history, she appeared very worried because of not hearing since the day before, the usual clicking noise of her mechanical mitral valve prosthesis. The metallic bileaflet-tilting—disk valve (St Jude Medical, Inc.) had been implanted 10 years before. Anticoagulant therapy (acenocumarol) was interrupted before the colon surgery, and the patient was receiving low-molecular weight heparin (nadroparin 5,700 UI bid). On physical examination, the heart rate was 100 beats per minute, blood pressure was 90/50 mmHg, and respi-ratory rate was 18 breaths per minute. Auscultation of the heart revealed an absence of a prosthetic closure sound and a grade III holosystolic murmur in the mitral area. Rales were present at both lung bases. A transthoracic echocar-diogram, immediately performed, revealed severely restricted movement of the prosthetic mitral valve leaflets with an increased peak diastolic transmitral pressure gra-dient (Fig. 1a). Unfractioned heparin was commenced immediately. The idea of arranging a transfer to another hospital for cardiac surgery was rejected because of the high operative risk and the presence of co-morbidities. The hemodynamic status indeed rapidly and dramatically worsened, with the clinical evidence of cardiogenic shock. Notwithstanding the recent abdominal surgery, systemic thrombolysis was adminis-tered (rt-PA 100 mg over 120 min). The patient's hemodynamic status rapidly improved, and a transthoracic echocardiogram, performed at the end of the rt-PA infu-sion, showed normalization of the transmitral flow pattern (Fig. 1b). The patient was discharged after a 2-week hos-pitalization on anticoagulant treatment. Prosthetic valve thrombosis is an infrequent but poten-tially life-threatening complication with a reported incidence of 0.5–8% of left-sided valves and up to 20% of tricuspid valves [1–3]. Reoperation, the traditional treat-ment of severe prosthetic thrombosis is associated with significant morbidity and mortality particularly in critical patients [4, 5]. Evidence is growing that fibrinolysis can be considered as the first-line treatment in the absence of contraindications [6]. Although recent (less than 2 weeks) major surgical procedures usually exclude the possibility of fibrinolysis in myocardial infarction [7], this condition is not considered a contraindication for treating obstruction of prosthetic valve in critically ill patients [8] where a totally different balance of risks and benefits exists.