Freedom from thromboembolism despite prolonged inadequate anticoagulation.

Life-long and meticulous control of anticoagulation is mandatory following mechanical valve replacement to prevent thromboembolism. Two patients who underwent mechanical mitral valve replacement with third generation bi-leaflet valves and in whom therapeutic anticoagulation could not be achieved for many months postoperatively form the basis for this report. In the first patient, the target international normalised ratio (INR) of 2.5-3.5 could not be achieved until 53.5 months postoperatively despite good compliance with oral anticoagulation and INR monitoring. In the second patient, the target INR was achieved after 16.9 months of oral anticoagulation treatment and regular INR monitoring. No thromboembolism occurred in either patient; nor did any valve-related event occur. The two patients are in excellent physical health 8 and 5 years, respectively, after the procedure. This unusual phenomenon is reviewed in light of the few reported cases of patients with mechanical heart valves surviving for prolonged periods without anticoagulation.