A cardiac monitoring device includes: at least one sensing electrode for obtaining an electrocardiogram (ECG) signal from a patient； a processing unit comprising at least one processor operatively coupled to the at least one sensing electrode； and at least one non-transitory computer-readable medium comprising program instructions that, when executed by the at least one processor, causes the cardiac monitoring device to: obtain the ECG signal from the at least one sensing electrode； determine a transformed ECG signal based on the ECG signal； extract at least one value representing at least one feature of the transformed ECG signal； provide the at least one value to determine a score associated with the ECG signal, thereby providing an ECG-derived score； compare the ECG-derived score to a predetermined threshold score determined by machine learning； and provide an indication of a cardiac event if the ECG-derived score is one of above or below the predetermined threshold score determined by the machine learning.
