The disclosure herein provides cardiac monitoring and diagnostic system, methods, and devices. A cardiac diagnostic system for detecting potential indicators of cardiac disease comprises: a cardiac monitoring device comprising at least one electrode configured to detect an analog electrical cardiac signal of a user； a cardiac signal filter configured to convert the analog electrical cardiac signal to digital electrocardiogram data； an atypical cardiac sequence detector configured to detect atypical cardiac patterns in the electrocardiogram data that are potentially indicative of cardiac disease； and a notification transmitter configured to generate an alert when a detected atypical cardiac pattern is determined to be indicative of cardiac disease.
