A medical system for sensing and regulating cardiac activity of a patient may include a cardioverter that is configured to generate and deliver shocks to cardiac tissue and a leadless cardiac pacemaker (LCP) that is configured to sense cardiac activity and to communicate with the cardioverter. The cardioverter may be configured to detect a possible arrhythmia and, upon detecting the possible arrhythmia, may send a verification request to the LCP to help conform that the possible arrhythmia is occurring. The LCP, upon receiving the verification request from the cardioverter, may be configured to activate one or more of a plurality of sensors to attempt to help confirm that the possible arrhythmia is occurring.