The goal of clinical trial is to prospectively collect data to investigate the prevalence of arrhythmia in young patients diagnosed with mitral annular disjunction who have no indication for implantable cardioverter defibrillator (ICD) or implantable loop recorder (ILR) implantation according to the current guideline. The study population is young (age 18-60), the participating patients have mitral annular disjunction confirmed by echocardiography and MR scan confirmed late-type gadolinium enhancement in the myocardium. This patient population has an increased risk of ventricular arrhythmias and sudden cardiac death. The investigators plan to implant 20 BioMonitor IIIm ILRs over a year in patients with mild or uncertain symptoms (dizziness, palpitations) and no malignant arrhythmias.

Aims of the study:

1. Screening of asymptomatic patients with MAD for arrhythmia.
2. In case of symptoms, to prove or exclude the underlying arrhythmia.

BioMonitor IIIm ILR implantation is planned in the following patient population:

1. Inclusion of 20 patients with mitral annular disjunction confirmed by echocardiography and late gadolinium enhancement in the myocardium by MRI.
2. Only patients who do not meet the current indication for ICD or ILR implantation based on the current recommendation will be included in the study.

Inclusion Criteria:

• age between 18 and 60 years
• patient not incapacitated
• mitral annular disjunction confirmed by echocardiography
• MR scan confirmed late-type gadolinium enhancement in the myocardium

Exclusion Criteria:

• lack of informed consent
• age under 18 years
• limited capability
• guardianship
• active infection
• cancer
• previous ICD implantation
• indication for ICD or ILR implantation based on current recommendation