Sick Sinus Syndrome

Sinus node is the natural pacemaker of the heart which gives out regular electrical pulses to produce each heartbeat. When it is diseased, this function is defective and called sick sinus syndrome.
Sinus node, known in short as SA node, is situated in the right upper part of the heart. Normally it gives out 60 to 100 pulses per minute so that heart beats at the same rate. When you exercise or are having a stress, the rate increases gradually.
When the sinus node stops functioning, it can manifest as a long pause in the ECG, the recording of the electrical activity of the heart.
Just as the next senior person takes charge in the office if the boss is on leave, when sinus node stops functioning, the next relay station in the heart known as AV node may take over the function. AV node has a lower pulse rate and heart rate will be slower, known as junctional rhythm. AV node is at the junction between the upper and lower chambers of the heart.
If AV node is also defective, a long pause in the heart beats can occur and the person can faint. Occasionally there could be an irregular rhythm originating from the upper chambers of the heart known as atrial fibrillation.
When both long pauses and fast irregular rhythms occur intermittently, it is known as tachy-brady syndrome. Tachy means fast and brady means slow.
Atrial fibrillation, known in short as A-FIB causes almost standstill of the upper chambers. This is because the upper chambers cannot contract well along with the very fast electrical activity. But the rate of the lower chambers is lower as many of the very frequent electrical signals from the upper chambers, is blocked by the AV node.
In atrial fibrillation, due to the poor contractions of the upper chambers, blood clots can form in the upper chambers.
Part of this clot can break away and move into the blood circulation. The clot travels along the blood vessels and may block any one of them. If a blood vessel of the brain is blocked, it results in weakness of a side known as stroke. This animation video shows a clot travelling up to left side of the brain and blocking a blood vessel there.
What do we do about it if the heart rate is very low in sick sinus syndrome? We can give a device known as pacemaker, which is implanted under the skin and connected to the heart with leads introduced through the blood vessels. The device will give electrical pulses to restore regular contractions of the heart at a normal rate.
If there is atrial fibrillation, blood thinners can be given to prevent clot formation within the heart. This will prevent migration of clot and the occurrence of stroke.