by P. Bobby

Created on: December 15, 2008

Do you have an elderly relative, a great aunt perhaps, who is on medication for their heart and was having episodes of shortness of breath, feeling light-headed, and dizziness even to the point of losing consciousness and collapsing? Has this relative required the insertion of a pacemaker perhaps? Chances are that this relative has Sick Sinus Syndrome (SSS).

The human heart beats an average eighty times in a minute or 100,000 times in one day. With each beat is pumped blood rich in oxygen and essential nutrients. This blood infuses all our tissues, squeezed through tiny capillaries to replenish vital organs such as the brain. Pressure within the blood vessels, maintained by the regular synchronous beating heart, coupled with the compliance of the vessel wall - much like filling a balloon with water, only on a microscopic level maintains a continuous yet pulsating flow of blood and sustains life as we know it.

The human brain does not function without the constant replenishment of oxygen and nutrients that the blood brings. The heart pumps one litre of blood to the brain every minute. Four seconds with no heartbeat renders a person unconscious, 4 minutes permanently brain-damaged.

Second by second, minute by minute, day by day, the heart is timed to perfection by a hidden electrical system deep within its muscle fibres, telling the heart when to pump. This is a rhythmic automatic process requiring no conscious effort. An electrical impulse begins at the top of the heart and moves progressively and quickly down, coordinating a rhythmic contraction of the hearts muscle and propulsion of the blood.

This rhythmicity of the heart is the key to its regular beating. And it all begins in a small area at the top of the heart. This sino-atrial (SA) node is the heart's internal clock its pacemaker'. The number of times the SA node fires an impulse in one minute, equates to the number of times the heart beats in a minute; at least when the heart is healthy and normal.

When there is dysfunction of this internal pacemaker i.e. an abnormality with the SA node the frequency and coordination of regular contractions is (partly) disabled. And the rhythmic propulsion of the blood flow is reduced significantly. In turn the brain is not replenished of nutrients adequately, and we begin to feel light-headed and dizzy at first, progressing to the point of feinting and if the situation persists for more than a few seconds, we collapse. This is Sick Sinus Syndrome when the heart's internal pacemaker or SA node is firing inadequately.

Sometimes when the SA node is dysfunctional or diseased it can beat very rapidly and often in an irregular fashion. This condition, known as atrial fibrillation, can also present with similar symptoms as SSS, because the coordinated rhythmic beating is lost and the heart does not have time to fill with enough blood for each pump. Often people with SSS have fleeting or sustained episodes of slow, normal and fast regular or irregular heart beats, including episodes of atrial fibrillation or atrial flutter.

The likely cause of sick-sinus syndrome is coronary artery disease however, anything that damages the SA node can cause the syndrome. Treatment usually requires an implantable external pacemaker.

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