Assessment by one of the places obviously is incorrect. It is always good and desirable to have assessment done by the cardiologist who was following you before and after surgery and serial echos are very useful. TE echo is a very reliable investigation. Your having no symptoms makes the possiblity of a malfunction less likely. I hope you are meticulously taking the anticoagulants. A repeat echo at one month is a good idea in view of the discrepancy. It is also good to consult the surgeon who had operated on you since he would be in a good position to guide you regarding the maximum permissible gradient for the size of valve used on you.