Sinoatrovial Node (SA node) is the heart's natural pacemaker. It's a small mass of specialized cells on top of the heart's right atrium (upper chamber). It is responsible for the electrical impulses that make the heart beat. When an electrical impulse moves across a chamber of the heart, it will contract. The signal must travel down a specific path to reach the ventricles, the heart's lower (pumping) chambers.
Some people experience abnormal heart rhythms to the point that it becomes too dangerous. That can happen in a sudden and unexpected way that sometimes those who are affected die as the result. To correct these abnormal rhythms, an Implantable Cardioverter Defibrillator (ICD) is inserted just under the collar bone. It gives your heart electric pulses to get your heart rhythm back to normal. AHA suggests that ICD constantly monitors the heart rhythm through the electrodes and whenever a dangerous heart rhythm is noticed, it can do three things to correct it:
• Pacing – makes use of a series of low-voltage electrical impulses at a fast rate to correct the heart rhythm
• Cardioversion – makes use of small electric shocks to try and restore the heart to a normal rhythm
• Defibrillation – makes of larger electric shocks to try and restore the heart to a normal rhythm
When the ICD has already been implanted, it is a requisite to make regular check ups with the doctor so that the ICD will be properly monitored and checked if the device is properly sensing the heartbeat, to monitor how much shocks have been delivered, and if the batteries are still capable of providing power to the device.