The goal of this observational study is to determine the feasibility of detecting abnormal heart rhythms, known as arrhythmias, by recording Electrocardiogram (ECG) and Photoplethysmogram (PPG) waveforms from the ears in patients who have already been diagnosed with arrhythmias. The main questions it aims to answer are:

• Can ECG and PPG signals from the ears reliably detect arrhythmias?
• How do ear-based ECG/PPG waveforms compare to standard single-lead ECG in detecting abnormal rhythms?

Researchers will compare data from healthy controls and arrhythmia patients to see if ear-based recordings are as effective as traditional methods.

The main goal of this study is to determine the feasibility of detecting abnormal heart rhythms, known as arrhythmias, by recording Electrocardiogram (ECG) and Photoplethysmogram (PPG) waveforms from the ears.

The study includes both healthy control subjects and patients who have already been diagnosed with arrhythmias. These individuals will be approached by a clinical member of the research team during their hospital stay or outpatient visit at Imperial College NHS Trust (ICHNT). Patients will be given comprehensive information about the study through a patient information sheet and will be asked for their written informed consent, with adequate time provided for questions and understanding.

To capture Ear-ECG/PPG waveforms, a variety of standard medical-grade sensors and electrodes will be placed in and around both ears. These include standard EEG electrodes on each mastoid secured with medical-grade gel, and an in-ear foam-based earpiece (like commercial earplugs) with cloth electrodes. An additional PPG sensor (MAX30101 from Maxim Integrated) will be attached to the back of the ear with adhesive medical tape. The patient will also be connected to a standard single-lead ECG and a blood pressure cuff, already part of their standard care on the hospital ward.

Once the setup is complete, each patient will follow 3 different recording protocols displayed on a screen. Patients will be asked to sit upright (Protocol 1) and engage in a series of simple activities with designated breaks in between, including head movements, counting aloud to 60, chewing gum (or simulating chewing), walking (if able) freely under medical supervision with assistance if needed (Protocol 2), slow controlled breathing and immersing their hand in cold water (Protocol 3). The total recording time including setup will be approximately 20 minutes.

Inclusion Criteria:

• Able to give informed consent;
• Healthy and diagnosed with cardiac arrhythmias.

Exclusion Criteria:

• No abnormal ear anatomy

50 healthy patients and 50 patients with an established diagnosis of cardiac arrhythmias

Held within Imperial College London as per standard local data protection guidelines. Data may be considered for sharing upon reasonable request.