The goal of this clinical trial is to answer the question whether a transcutaneous stimulation of a certain nerve (Nervus vagus) with a dedicated device reduces the recurrence of the heart rhythm disorder atrial fibrillation.

Participants will receive a dedicated nerval stimulation device and will treat themselves on a daily basis for at least an hour per day. Treatment will last for 3 months. Researchers will compare this group with a similar group that uses an ineffective device. Both researcher and patients will be blinded so they do not know which device they will be using.

This study is an investigator-initiated, monocentric, randomised, controlled and blinded trial. Patients with persistent atrial fibrillation and planned electrical cardioversion will be included. The participants are randomised to one of two groups - the verum-group or the sham-group. Both groups receive a dedicated stimulation device that stimulates transcutaneously the Ramus auricularis of the Nervus vagus at the area of the Tragus. The verum-group will receive an effective stimulation and the sham-group an ineffective one. The aim of this trial is to evaluate whether this stimulation could reduce the recurrence of atrial fibrillation or not. Therefore daily stimulation of at least one hour will be performed for overall three months. After that period the stimulation will be withdrawn and both groups will be compared. Then, after another three months without stimulation both groups will be compared again to evaluate if a potential effect of the initial stimulation persists.

Inclusion Criteria:

• Persistent atrial fibrillation
• Planned electric cardioversion
• Sufficient oral anticoagulation for at least four weeks or
• Absence of thrombus in transoesophageal echocardiography
• Oral anticoagulation possible
• Able to sign informed consent
• Estimated life expectancy >1 year

Exclusion Criteria:

• Permanent atrial fibrillation
• Ablation therapy of supraventricular arrhythmias in the past
• Missing anticoagulation respective missing rule out of thrombus
• Inability to treat with oral anticoagulation
• Latent or manifest hyperthyroidism
• Acute infection with relevant clinical signs (temp > 38°C, significant elevated C-reactive protein or white blood cells)
• Inability to sign informed consent
• Preexisting pacemaker or implantable cardioverter defibrillator
• Recent vagal stimulation for other causes
• Recent intolerance of transcutaneous vagal stimulation
• Estimated life expectancy <1 year
• Acute coronary syndrome
• Haemodynamic instability
• Valvular atrial fibrillation
• Pregnancy

All participants are randomized 1:1 to either the verum- or the sham-group. Both device look similar and are used in the same way so the participants are blinded. This is achieved with a conducting and a non-conducting ear electrode.

The care provider and the investigator is blinded as well. The researcher who randomises the patient is strictly separated from the investigator who is responsible for the follow-up. Only after the patient completed the last follow-up the outcome assessor will match the patient data with the affiliation to either the sham- or the verum-group.