During an Arrhythmia

What happens in the heart during an arrhythmia?

The normal heart is a strong, hardworking, muscular pump. A person's heart, when normal sized, is slightly larger than his or her fist. Describing how the heart beats normally helps to explain what happens during an arrhythmia.

The heart is divided into right and left sides; there's an upper and lower chamber on each side. The right and left atria (upper chambers) receive blood from the body and the lungs. The right and left ventricles (lower chambers) are the muscular chambers. They pump blood out of the heart to the lungs and body.

As blood travels through the heart, it moves through a series of valves. The valves open and close to let blood flow in only one direction.

Each heartbeat begins when a specialized area of the right atrium (the sinus node or S-A node, which is also called the heart's pacemaker) generates a small amount of electricity. Each electrical signal leaves the sinus node and spreads into the muscle cells of the heart's atria. This causes them to contract.

The electrical activity then moves into the junction between the atria and ventricles. There it passes through the atrioventricular node (A-V node). The A-V node acts as a relay station. It takes the signal coming from the atria, delays it slightly, and then passes it into the ventricles, causing them to beat.

Usually the whole heart contracts between 60 and 100 times per minute with beats spaced evenly. Each contraction equals one heartbeat. This is called normal sinus rhythm.

An arrhythmia may occur for one of several reasons:

• Instead of beginning in the sinus node, the heartbeat begins in another part of the heart.
• The sinus node develops an abnormal rate or rhythm.
• The signal bypasses the normal regulation of the AV node
• A patient has a heart block.

How does the doctor know that I have arrhythmia?

Arrhythmia's (also called dysrhythmias) may occur at any age. Sometimes a person may not be aware they have an arrhythmia.

The usual ways to evaluate a rhythm abnormality are similar to those used to evaluate other health problems. The patient's history is very important. Questions like these might be asked:

• Are you aware of unusual heartbeats?
• Does anything bring on the arrhythmia? What can you do, if anything, to make it stop?
• If it's a fast rate, how fast?
• Do you feel weak, lightheaded or dizzy?
• Have you ever fainted