A device, comprising: one or more electrodes (500, 502, 504, 506, 508, 510); a sensing circuity (544, 550) coupled to the one or more electrodes (500, 502, 504, 506, 508, 510) and configured to obtain a signal indicative of cardiac electrical activity; and at least one of a processor or controller configured to detect a potential R-wave within the signal indicative of cardiac electrical activity; determine a measure of magnitude of a first portion of the signal corresponding to a first window that follows the potential R-wave; and determine the measure of magnitude of a second portion of the signal corresponding to a second window that follows the first window, wherein the at least one of a processor or controller is further configured to: determine whether the measure of magnitude of the second portion of the signal is at least a specified extent larger than the measure of magnitude of the first portion of the signal; and classify the potential R-wave as a false R-wave, in response to determining that the measure of magnitude of the second portion of the signal is at least the specified extent larger than the measure of magnitude of the first portion of the signal. one or more electrodes (500, 502, 504, 506, 508, 510); a sensing circuity (544, 550) coupled to the one or more electrodes (500, 502, 504, 506, 508, 510) and configured to obtain a signal indicative of cardiac electrical activity; and at least one of a processor or controller configured to detect a potential R-wave within the signal indicative of cardiac electrical activity; determine a measure of magnitude of a first portion of the signal corresponding to a first window that follows the potential R-wave; and determine the measure of magnitude of a second portion of the signal corresponding to a second window that follows the first window, wherein the at least one of a processor or controller is further configured to: determine whether the measure of magnitude of the second portion of the signal is at least a specified extent larger than the measure of magnitude of the first portion of the signal; and classify the potential R-wave as a false R-wave, in response to determining that the measure of magnitude of the second portion of the signal is at least the specified extent larger than the measure of magnitude of the first portion of the signal. detect a potential R-wave within the signal indicative of cardiac electrical activity; determine a measure of magnitude of a first portion of the signal corresponding to a first window that follows the potential R-wave; and determine the measure of magnitude of a second portion of the signal corresponding to a second window that follows the first window, wherein the at least one of a processor or controller is further configured to: determine whether the measure of magnitude of the second portion of the signal is at least a specified extent larger than the measure of magnitude of the first portion of the signal; and classify the potential R-wave as a false R-wave, in response to determining that the measure of magnitude of the second portion of the signal is at least the specified extent larger than the measure of magnitude of the first portion of the signal. determine whether the measure of magnitude of the second portion of the signal is at least a specified extent larger than the measure of magnitude of the first portion of the signal; and classify the potential R-wave as a false R-wave, in response to determining that the measure of magnitude of the second portion of the signal is at least the specified extent larger than the measure of magnitude of the first portion of the signal.