Arrhythmia

What is an Arrhythmia?

Arrhythmias are abnormal changes in pattern and/or changes in speed from the normal heart rhythm. Some changes in the speed of the heart rhythm (heart rate) are quite normal, for example, when the heart speeds up during exercise or slows down when you are resting or when you are asleep. Arrhythmias occur for different reasons but usually indicate that there are changes, possibly diseases, in the heart, of which some are more serious than others. With regard to more common arrhythmias and their consequences:

• A slow heartbeat is called a bradycardia and a rapid heartbeat is called a tachycardia.
  
  
• Arrhythmias can occur in both the upper chambers of the heart (called the atria) and the lower chambers (called the ventricles), for example, ventricular tachycardia.
  
  
• Both tachycardias and bradycardias can lead to lack of blood flow to the brain, the coronary arteries (supplying the heart muscle), or the rest of the body.
  
  
• Arrhythmias can lead to lack of blood flow to the brain causing dizziness or loss of consciousness (fainting or syncope).
  
  
• Lack of blood supply to the coronary arteries can cause chest pain or pressure (angina). Inadequate blood supply to the rest of the body can cause weakness and shortness of breath.

How do you get Arrhythmias?

Arrhythmias usually happen when the heart is injured or damaged, for example, in heart valve disease, heart failure, heart muscle disease, during attacks of angina or after a heart attack.

• The kind of arrhythmia depends on which part of the heart is affected.
  
  
• Normally, electrical signals pass around the heart in an well-organised system of special cells that keep it beating in a regular and organised manner.
  
  
• Arrhythmias are caused by abnormal electrical signals within the heart being produced by injury that disrupts the normal pattern; for example, in the upper chambers, this could result in atrial fibrillation or tachycardia.

The most serious kind of arrhythmia is called ventricular (lower chamber) fibrillation because it means the heart rhythm is beating rapidly in a totally disorganised manner and the heart is no longer able to pump blood around the body.

How serious are Arrhythmias?

Arrhythmias suggest the presence of heart disease and are serious because they can lead to sudden death. They may also have an impact on quality of life if they are not treated because they result in chest pain, weakness, shortness of breath and fainting. These symptoms are themselves very alarming and distressing and may limit everyday activity.

How long do Arrhythmias last?

This depends on the cause and source of the arrhythmia. Atrial fibrillation, which means the upper chambers (atria) are beating rapidly in a disorganised manner, can be present for months or years. Fortunately, it is usually controlled with medicines. Other arrhythmias may last only a short period of minutes as in ventricular tachycardia or fibrillation.

How are Arryhthmias treated?

Tachycardias involve a rapid and sometimes disorganised beat. These include atrial fibrillation, atrial flutter, atrial tachycardia, and ventricular fibrillation. They are managed with medicines that include calcium-channel blockers, beta-blockers and digoxin. There are other anti-arrhythmic drugs that can be used. Also, there are other forms of treatment that can be recommended if medicines don't work.

• Certain types of calcium-channel blockers work on the cells of the heart by dampening down the abnormal electrical activity and making the heart less excitable so restoring a more normal rhythm.
  
  
• Beta-blockers work by slowing the rate of the heart and the force of its beating. They do this by blocking chemicals called noradrenaline, which comes from the nerves in the heart, and adrenaline, which is carried in the blood. This has the effect of resting the heart and making it less excitable and, therefore, less likely to have abnormal electrical activity and arrhythmias.
  
  
• Digoxin, sometimes called digitalis, works by slowing down the speed of electrical pulses in the heart that control its rhythm. This is useful where there is a rapid arrhythmia because it allows the normal electrical signals to take control again.

The goal of treatment is to slow down the rate of ventricular contractions and to bring the heart rate back to normal.

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