An implantable
medical device is configured determine a numerical value of a variable that is monitored by the implantable
medical device and convert the numerical value to a data sequence of modulated electrical
stimulation rate intervals. The implantable
medical device delivers electrical stimulation pulses according to the data sequence of modulated
stimulation rate intervals to cause a modulated rate of activation of excitable tissue of a patient corresponding to the modulated
stimulation rate intervals. The modulated rate of activation is detectable by a rate monitor for
demodulation to the numerical value of the monitored variable
data value. In some examples, the implantable medical device is a pacemaker delivering
cardiac pacing pulses according to modulated pacing rate intervals to cause a modulated
heart rate of the patient detectable by a
heart rate monitor for
demodulation to the numerical value of the monitored variable.