An implantable medical device includes a sensor and a T-wave analyzer. The
sensor is implantable within the body of a patient to sense electrical
cardiac activity and provide an indication of T-wave alternans within the
heart of the patient. The T-wave analyzer is responsive to the sensor, and
evaluates cardiac risk based on comparison of the indication of T-wave
alternans to a predetermined criterion. The T-wave analyzer may form part
of a microprocessor, a digital signal processor, or combination of both.
The device may include a pacing generator that applies increased rate
pacing stimuli to the heart to facilitate sensing of the T-wave alternans
by the sensor. The device also may incorporate a memory that stores the
T-wave alternans indication provided by the sensor, e.g., over a number of
heartbeats. In addition, the device may be equipped to provide an alert to
the patient or a physician in the event the processor generates the
indication of cardiac risk. The results of the T-wave alternans analysis
over a period of time can be stored as data in memory for access by a
physician, e.g., by telemetry. In response to the alternans data, the
physician may prescribe pharmacologic therapy, programmed cardiac
electrical stimulation, or modifications to an electrical stimulation
program in the existing implanted device. In some cases, the implantable
medical device can be programmed to response to the alternans data, e.g.,
by controlling a pacing generator.
