Electrodes continuously monitor the heart's electrical activity and send data through the leads to the computer part. If there is an abnormal heart rhythm, the computer tells the generator to send electrical pulses (as programmed by the doctor) to the heart. This "pacing" adjusts the heartbeat: if the heart rate is too, slow the device "paces" by sending a small electrical signal to the heart muscle, causing it to contract. The pacemaker is also capable of storing the information it collects about the heart, helping the doctor evaluate the therapy and adjust the pacemaker settings as needed.

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