This study evaluates the function of the heart in young patients with muscular dystrophy type Duchenne or Becker. Participants have their hearts examined at regular intervals by ultrasound (echocardiography) and cardiac magnetic resonance imaging.

Muscular dystrophy leads to progressive loss of function in all muscles during childhood and adolescence, including the heart. The usual method to evaluate the heart is echocardiography, emphasizing few parameters. Cardiac magnetic resonance imaging is not as widely available as echocardiography, but early changes can be detected before they become visible on echocardiography. In this study, the investigators compare the methods of measuring heart function in order to find the best measurements for follow up and to see how fast the degenerative changes occur in the hearts of patients with muscular dystrophy.

Inclusion Criteria:

• Boys aged 8 to 18 years with DMD/BMD confirmed genetically or by muscle biopsy
• Informed consent

Exclusion Criteria:

• Other clinically significant concomitant disease states (e.g., renal failure)
• Inability to follow the procedures of the study, e.g. due to language problems, psychological disorders, dementia, etc. of the participant or his/her parents or legal caregivers,
• Inability to lie still for the duration of the imaging procedures (approximately 45 minutes each for echocardiography and CMR)
• MR-incompatible implanted or accidentally incorporated metal device or claustrophobia that prohibits use of magnetic resonance imaging

• Boys aged 8 to 18 years with DMD/BMD confirmed genetically or by muscle biopsy
• Control group for CMR: children without heart disease