Case report of a young female patient, 27 years old. The patient was born with congenital heart defect-extreme form of tetralogy of Fallot with pulmonary valve atresia. In the neonatal period she underwent Blalock-Taussig anastomosis and later the Rastelli operation with the implantation of homograft in pulmonary position. During time there was calcification and narrowing of the conduit and at the age of 26 she went in the international center for the mechanical heart valve implantation in pulmonary position. As a young patient she did not understand the importance of follow-up and did not continue treatment in Croatia since she felt good. She stopped taking prescribed medications, including anticoagulant therapy. One year after the operation she gave birth to a healthy child and after she was sent to control cardiac examination. Heart ultrasound was preformed which verified the mechanical pulmonary valve completely stiff in the open position with the presence of mobile clots. Patient, in a relatively short period after implantation of mechanical valve, was re-operated in our clinic with excellent postoperative result. The case of this patient wishes to emphasize the importance of forming Center for congenital heart diseases where the young patients in adulthood could be carefully monitored and treated. (1-3) The patient had the great fortune that the mechanical valve was fixed in hemodynamic relatively favorable position and has been without major problems.