A medical system comprising a control device (referred to as a "planet") and a plurality of sensing and stimulating devices (referred to as "satellites") is disclosed. The satellites are relatively small devices that can be thoracoscopically attached to an exterior surface of the heart. The planet can be implanted if desired or, alternatively, externally retained. The planet is capable of wirelessly communicating (i.e., without a direct electrical connection) to each satellite. The planet individually commands each satellite to deliver pacing energy to the heart. Additionally, each satellite is capable of determining when a sense event has occurred at the site of that satellite and transmitting an encoded signal to the planet indicating that a sense event has occurred, along with an identifying code indicating to the planet which satellite detected the sense event. The planet processes the encoded signals received from the network of satellites, assigns time values to each satellite when that satellite detects a sense event, compares the time values to a template of normal values, and determines if an arrhythmia has occurred if the time values do not match the template. Further, the planet selects and implements an appropriate pacing protocol to terminate the arrhythmia. The satellites derive their needed power from signals received from the planet via the wireless communication path.