Abstract: Systems and methods are described herein for detecting disturbances in cardiac signals. An electrode apparatus includes a plurality of external electrodes to be disposed proximate a patient's skin. A computing apparatus includes processing circuitry. The computing apparatus is operably coupled to the electrode apparatus. The computing apparatus is configured to monitor electrical activity from tissue of a patient using a plurality of external electrodes to generate a plurality of electrical signals. At least one of the electrical signals of the plurality of electrical signals is filtered. At least one disturbance in the at least one electrical signal is detected using the at least one filtered signal. A temporal location of the at least one disturbance in the at least one electrical signal is determined based on a time that the at least one filtered signal crosses a predetermined threshold.