Abstract: An implantable medical device includes a housing. An opening is present in the housing. The implantable medical device includes an antenna in the housing, where the antenna is located below the opening. The implantable medical device includes a cover coupled to edges of the housing defining the opening to close the opening. The cover enables passage of radio frequency signals at one or more communication frequencies to and from the antenna. The implantable medical device also includes an antenna shield positioned above the cover. The antenna shield reduces passage of radio frequency signals to and from at least a portion of the antenna during use.

Abstract: A method of treating a medical condition in a patient using an implantable medical device, comprising providing an electrical signal generator; providing at least a first electrode operatively coupled to the electrical signal generator and to a vagus nerve of the patient; sensing cardiac data of the patient; determining at least a first cardiac parameter based upon said cardiac data; setting at least a first value; declaring an unstable brain state of a patient from said at least a first cardiac parameter and said at least a first value; and adjusting the at least a first value. Also, a computer readable program storage device encoded with instructions that, when executed by a computer, performs the method. In addition, the implantable medical device used in the method.