This study aims to assess the feasibility and reliability of smart watch iECG provided by the Apple Watch/Apple iPhone for the detection of different cardiac arrhythmias. In this study, results from a 12-lead ECG will be set as the gold standard for the arrhythmia diagnosis, and results from the smart watch iECG (Apple watch/Apple iPhone application and Cardiologist's interpretations) as the index tests. The iECG tracings will be recorded simultaneously, starting and ending at the same time as the standard 12-lead ECG, using the built-in sensors of a smart watch (Apple Watch Series 4) with the ECG application.

This diagnostic accuracy study is an investigator-initiated trial to evaluate the value of a smart watch-based iECG for detection of cardiac arrhythmias.

iECG tracings will be recorded simultaneously, starting and ending at the same time as the standard 12-lead ECG, using the built-in sensors of a smart watch (Apple Watch Series 4) with the market version of the ECG application (Apple Inc., California). Participants will be advised to lie down in a supine position and breathe spontaneously. All recording will be done by trained study personnel.

All iECG and 12-lead ECG recordings will be presented in PDF format as our references. Saved formats will be transferred to our Telemonitoring Center for further analysis and processing.

Results from a 12-lead ECG will be considered as the gold standard for the measurement of heart rhythms and the arrhythmia diagnosis. All 12-lead ECGs recordings will be analyzed by 2 blinded cardiologists and will be categorized as "Sinus rhythm", "High or low heart rate", "Atrial fibrillation", or "Inconclusive". Besides, cardiologists will report ECG wave's characteristics as well as any other possible diagnosis including "Superior ventricular tachycardia", "Ventricular tachycardia", "Atrial flutter", and "other types: other possible arrhythmias". In the case of uncertainties, a third cardiologist will be consulted, blinded for initial diagnoses.

The iECG recordings (test index) will be interpreted and reported in two different ways:

1. By using HealthKit Framework (Apple Watch and Apple iPhone applications): After a successful iECG recording with the Apple watch, iECGs will be transmitted by the ECG application to the iPhone. The Health App (Apple Inc., California) will receive, process and store the iECGs on the iPhone and will present one of the following results on the iPhone screen automatically: "Sinus rhythm", "High or low heart rate", "Atrial fibrillation", or "Inconclusive". Besides, the mean heart rate will be recorded, which will be automatically calculated by the Health App.
2. By cardiologist: All iECGs will be analyzed by 2 blinded cardiologists. They will report their findings in the following categorize: "Sinus rhythm", "High or low heart rate", "Atrial fibrillation", or "Inconclusive". Besides, they will report ECG wave's characteristics as well as any other possible diagnosis including "Superior ventricular tachycardia", "Ventricular tachycardia", "Atrial flutter", and "other types: other possible arrhythmias". In the case of uncertainties, a third cardiologist will be consulted, blinded for initial diagnoses.

ECG wave's characteristics: The following variables will be measured as the iECG and 12-lead ECG waves' characteristics. Three randomly chosen heartbeats will be considered to measure each wave or interval, and the mean of these 3 measurements will be used for statistical analysis.

Inclusion Criteria:

• Patients aged≥22 years at the time of eligibility screening will be included.
• Patients with known cardiac arrhythmias; i.e. AF before and after cardioversion, hemodynamically stable Bradycardias, SVT and VT during EP procedures and implants can also be included

Exclusion Criteria:

- Pregnancy

All individuals who had been admitted to the Department of Electrophysiology, Leipzig Heart Center