An implantable medical device (IMD) for gauging the severity of ischemia in a patient's heart includes a data collection module configured to receive data about the patient's heart, a data processing module configured to process the data to identify an episode of ischemia in the patient and to determine if the episode is stable or unstable, and a reporting module configured to provide an alarm to the patient if the episode is unstable. A method executable by an implantable medical device to detect ischemia in a human heart suitably includes the steps of receiving data about the heart at the implantable medical device, processing the data within the implantable medical device to determine the severity of ischemia, and providing a response from the implantable medical device to the patient if ischemia is indicated.