Effect of Trimetazidine on Coronary Flow in Transthyretin Cardiac Amyloidosis

The goal of this clinical trial is to learn if trimetazidine can improve blood flow in the heart in adults with transthyretin cardiac amyloidosis (ATTR-CM). ATTR-CM is a condition in which an abnormal protein builds up in the heart and can make it harder for the heart to work normally. The main question this study aims to answer is: Does trimetazidine improve the heart's ability to increase its blood flow when more blood is needed? The study will also look at whether treatment is linked to changes in walking ability, heart-related blood tests, heart function, and quality of life. Participants will: Take trimetazidine for about 6 months. Have heart blood flow measured with a positron emission tomography/computed tomography (PET/CT) scan before and after treatment. Have heart ultrasound examinations and blood tests. Complete a 6-minute walk test and a questionnaire about their symptoms and quality of life.