Systems, methods and devices for monitoring, analyzing, and processing a patient's heart rate signal for HRV characteristics are described herein. A first heart rate signal is acquired. The first heart rate signal includes at least one indication of an interval duration of cardiac activity. At least one accelerating portion and at least one decelerating portion of the first heart rate signal are identified. An average heart rate signal is acquired. The accelerating portion or the decelerating portion of the first heart rate signal is replaced with the average heart rate signal to produce a second heart rate signal. A frequency spectrum of the second heart rate signal may be obtained and utilized to predict or detect one or more autonomic conditions of a patient. Therapy may initiated or titrated in response to prediction or detection of the autonomic condition.