A device, comprising: one or more electrodes (700, 702, 704, 706, 708, 710); a sensing circuit coupled to the one or more electrodes (700, 702, 704, 706, 708, 710) and configured to obtain a signal indicative of cardiac electrical activity; and at least one of a processor or controller configured to determine, based on the signal indicative of cardiac electrical activity, information for at least three R-R intervals included in the signal, wherein each of the R-R intervals has a respective duration, and each of the R-R intervals may be a true R-R interval or a false R-R interval, characterized in that the at least one processor or controller is also configured to determine whether the duration of one of the R-R intervals is greater than a first specified threshold, determine whether the duration of the one of the R-R intervals is within a second specified threshold of being an integer multiple of at least X of the other R-R intervals for which information is obtained, wherein the integer multiple is at least 2, and wherein X is a specified integer that is 1 or greater, and determine whether to classify the one of the R-R intervals as being a false R-R interval, based on whether the duration of the one of the R-R intervals is determined to be greater than the first specified threshold, and based on whether the duration of the one of the R-R intervals is determined to be within the second specified threshold of being an integer multiple of at least X of the other R-R intervals for which information is obtained. one or more electrodes (700, 702, 704, 706, 708, 710); a sensing circuit coupled to the one or more electrodes (700, 702, 704, 706, 708, 710) and configured to obtain a signal indicative of cardiac electrical activity; and at least one of a processor or controller configured to determine, based on the signal indicative of cardiac electrical activity, information for at least three R-R intervals included in the signal, wherein each of the R-R intervals has a respective duration, and each of the R-R intervals may be a true R-R interval or a false R-R interval, characterized in that the at least one processor or controller is also configured to determine whether the duration of one of the R-R intervals is greater than a first specified threshold, determine whether the duration of the one of the R-R intervals is within a second specified threshold of being an integer multiple of at least X of the other R-R intervals for which information is obtained, wherein the integer multiple is at least 2, and wherein X is a specified integer that is 1 or greater, and determine whether to classify the one of the R-R intervals as being a false R-R interval, based on whether the duration of the one of the R-R intervals is determined to be greater than the first specified threshold, and based on whether the duration of the one of the R-R intervals is determined to be within the second specified threshold of being an integer multiple of at least X of the other R-R intervals for which information is obtained. determine, based on the signal indicative of cardiac electrical activity, information for at least three R-R intervals included in the signal, wherein each of the R-R intervals has a respective duration, and each of the R-R intervals may be a true R-R interval or a false R-R interval, characterized in that the at least one processor or controller is also configured to determine whether the duration of one of the R-R intervals is greater than a first specified threshold, determine whether the duration of the one of the R-R intervals is within a second specified threshold of being an integer multiple of at least X of the other R-R intervals for which information is obtained, wherein the integer multiple is at least 2, and wherein X is a specified integer that is 1 or greater, and determine whether to classify the one of the R-R intervals as being a false R-R interval, based on whether the duration of the one of the R-R intervals is determined to be greater than the first specified threshold, and based on whether the duration of the one of the R-R intervals is determined to be within the second specified threshold of being an integer multiple of at least X of the other R-R intervals for which information is obtained.