Ventricular arrhythmias are abnormal heart rhythms that arise from the bottom chambers of the heart. They can cause debilitating symptoms when they occur intermittently (these are called premature ventricular ectopics or PVCs) and can be life-threatening when they occur continuously (called ventricular tachycardia or VT). These are the most common causes of sudden cardiac death, especially in patients with pre-existing heart disease.

They can be a result of overactivation of the sympathetic nervous system, and in extreme circumstances, surgery to cut the nerve may be needed. A novel approach to target this nervous system using a transcutaneous electrical nerve stimulator (TENS) machine has successfully treated arrhythmias that come from the top chambers of the heart (atrial fibrillation). An ear clip is applied for an hour per day connected to a device (smaller than a phone) that can activate the parasympathetic nervous system (that counteracts the sympathetic nervous system). This is called Low-Level Tragus Stimulation (LLTS). Because it has been used for epilepsy for decades, we have evidence of a very high safety profile and tolerability. We plan to enrol 72 patients, 34 with many PVCs and 38 with VT, and randomise them to either first receive LLTS or first receive sham treatment (this will appear the same to the patient and researchers but without any meaningful vibrations being emitted in the sham group). Each patient will then swap over to the other treatment. We will compare whether the LLTS reduces the amount of ventricular arrhythmias during compared to the amount during the sham treatment period. We will use Holter monitors to measure the amount of PVCs after each period in the PVC group. VT patients have an implantable defibrillator that continuously monitors for VT episodes in this group. We will only enrol adults who can give informed consent, and study participation will not interfere with a patient's clinical treatment.

PVC Cohort

Inclusion Criteria:

• Age > 18 years old.
• Participants must understand and be willing to sign a written informed consent document.
• PVC burden of >10% in a 24-hour period on Holter monitoring.

Exclusion Criteria:

• Coronary artery disease
• Known cardiac disease (heart failure or cardiomyopathy) in the documented absence of PVCs. Individuals with suspected PVC-induced cardiomyopathy heart failure, defined as cardiomyopathy or heart failure only diagnosed in the setting of a >10% PVC burden, will be allowed to participate.
• A known diagnosis of Epilepsy.
• Ongoing pregnancy or intention to become pregnant in the forthcoming 12 months.
• Participants using a TENS device for any indication

VT cohort

Inclusion Criteria:

• Participants with structural heart disease and a transvenous implantable cardioverter defibrillator (ICD) in situ
• At least three clinically significant VT events (VT events defined as either >30 seconds of sustained VT, appropriate ICD ATP therapies or appropriate ICD shocks) in the six months before enrolment

Exclusion Criteria:

• Heart failure syndrome with inotrope dependency or requiring mechanical assistance.
• Reversible cause of arrhythmia (e.g. culprit electrolyte abnormality or toxin)
• NYHA (New York Heart Association) stage IV heart failure
• Myocardial infarction or cardiac surgery in the last six months
• Life expectancy <12 months
• Ongoing pregnancy or intention to become pregnant in the forthcoming 12 months.
• Participants using a TENS device for any indication