Method and system for detecting arrhythmias in cardiac activity (CA) obtain a far field CA data set including far field CA signals for beats. A feature enhancement function is applied to the CA signals to form an enhanced feature. An adaptive sensitivity level and sensitivity limit are calculated based on the enhanced feature from one or more beats within the CA data set and the method and a beat segment of interest is automatically iteratively analyzed by comparing the beat segment of interest to the current sensitivity level to determine whether one or more R-waves are present within the beat segment of interest. The iterative analyzing operation is repeated while progressively adjusting the current sensitivity level until i) the one or more R-waves are detected in the beat segment of interest and/or ii) the current sensitivity level reaches the sensitivity limit. An arrhythmia within the beat segment of interest is detected based on a presence or absence of the one or more R-waves and results of the detecting of the arrhythmia are recorded.
