Systems, methods, and computer program products identify arrhythmias experienced by a patient. A system includes an external wearable heart monitoring device for continuous and long-term monitoring of a patient that includes electrocardiogram (ECG) electrodes and circuitry to sense surface ECG activity and provide ECG channel(s) producing ECG signal(s), a non-transitory computer-readable medium including an arrhythmia classifier including neural network(s), and processor(s). The neural network(s) are trained based on a historical collection of ECG signal portions with annotation data including at least one annotation for each ECG signal portion and based on weight data including a weight for each annotation based on the annotator thereof. The processor(s) receive the ECG signal(s), monitor the ECG signal(s) to detect at least one arrhythmia event based on the arrhythmia classifier, and transmit at least one communication based on the arrhythmia event(s) to a remote computer system.