a middle lobe 64 during intense activity or exertion the heart rate is generally in upper lobe 66 abnormalities such as arrhythmias not controlled by pacing may cause readings of fast heart rates while at rest or abnormally slow heart rates during waking activities which fall outside their proper lobes such abnormalities are preferably revealed by comparing readings from accelerometer 46 fig1 to the heart rate measurements fig4 is a graph that schematically illustrates a function 70 used in controlling etc stimulation responsive to heart rate measurements in accordance with a preferred embodiment of the present invention the function gives the etc duty cycle as a function of measured heart rate and is applied by device 30 or by another suitable similar device in generating a sequence of etc signals such as that shown in fig2 a as described hereinabove the duty cycle of the etc stimulation is varied between minimum and maximum values preferably 0 and 100 by increasing or decreasing the number of signals 52 applied by etc circuit 36 during time period 54 the principle exemplified by function 70 is that etc stimulation is to be applied with greater intensity i e at higher duty cycle in proportion to the body 39 s demand for cardiac output thus below a minimum heart rate value preferably around 60 bpm corresponding generally to sleep and resting states of the patient the duty cycle is held at its minimum value no etc stimulation is applied since there is no need to.