*2.1. Mechanics of ECG*

' ECG is the practice of measuring the heart's electrical activity using pairs of electrodes on the skin. Clinically, this is achieved with 12 leads using 10 electrodes to measure cardiac signals from many angles [23]. A healthy ECG cycle typically consists of five different waves: P, Q, R, S, and T. The P-wave is the first positive wave and corresponds to atrial depolarization. The QRS complex, which consists of a negative Q-wave, a large positive R-wave, and a negative S-wave, represents ventricular depolarization and ventricular contraction. The T-wave represents ventricular repolarization and ventricular diastole [24]. Distortion of these waves can indicate abnormalities in the heart rhythm [25]. The Pan-Tompkins algorithm is commonly used to find the QRS complex in a regular ECG rhythm [26]. Al-

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though 12-lead ECGs provide the best clinical method for diagnosing arrhythmias, the switch to 3-lead ECGs or single-lead ECGs offers many advantages [23]. Cardiovascular patches that use adhesives have become increasingly popular due to their unobtrusiveness. For example, the FDA-approved Zio patch (iRhythm Technologies, Inc., San Francisco, CA, USA) has shown clinical suitability for detecting arrhythmias when compared with a 12-lead Holter monitor over 14 days [27].
