Cardiac Arrhythmias

Your heart rate is controlled by a complex electrical system within the heart muscle which drives it to go faster when you exert yourself and slower when you rest. A number of conditions can affect the heart rate or rhythm. Heart rate simply refers to how fast your heart is beating. Heart rhythm refers to the electrical source that is driving the heart rate and whether or not it is regular or irregular.

As some types of arrhythmias can cause you to faint without warning, your doctor may restrict your driving until the condition is controlled.

Some common terms:

• Sinus rhythm is the normal rhythm
• Arrhythmia means abnormal rhythm
• Fibrillation means irregular rhythm or quivering of one part of the heart
• Bradycardia means slow heart rate
• Tachycardia means fast heart rate
• Paroxysmal means the arrhythmia comes and goes

Tachycardia

The most common of these is atrial fibrillation. This is where your heart rhythm is irregular and often too fast. Symptoms include fatigue, palpitations (where you are aware of your heart racing or pounding), dizziness and breathlessness.

Other tachycardias include supraventricular tachycardia (SVT) or ventricular tachycardia (VT). These have similar symptoms to atrial fibrillation but can also cause you to lose consciousness (faint).

Bradycardia

The most common form of this is called heart block. This is because messages from the electrical generator of the heart don't get through efficiently to the rest of the heart and hence it goes very slowly or can pause. Symptoms of the heart going too slowly include feeling tired, breathless or fainting.

Tests

As well as having the following tests to diagnose what sort of arrhythmia you have, you might be investigated for evidence of heart diseases that cause arrhythmias with echocardiography, blood tests, or other tests looking for evidence of cardiovascular disease.

The first test you will have will be a resting electrocardiogram (ECG). The trace of the heart's electrical activity gives the diagnosis of the source of the arrhythmia. The resting ECG is often normal at rest and more extensive prolonged testing is needed to try and catch the arrhythmia especially if it is intermittent.

Ambulatory ECG (Holter monitor)
This test is used to monitor your heart for rhythm abnormalities during normal activity for an uninterrupted 24-hour period. During the test, electrodes attached to your chest are connected to a portable recorder - about the size of a matchbox - that is suspended in a pouch around your neck.

Event recorder
This is a test covering 1-2 weeks. You wear a small monitor  and if you have any symptoms, such as dizziness, you press a button on a recording device which saves the recording of your heart rhythm made in the minutes leading up to and during your symptoms. Because you can wear this for a longer period of time it has a higher chance of catching your abnormal rhythm.

Treatment

Tachycardia
Most treatments for these conditions consist of medication to stop the abnormal rhythm or make it slower if and when it occurs.

Bradycardia
Depending on how slow your heart goes and what symptoms you have you may be referred for a pacemaker. This is a small operation where a battery powered device is placed under the skin with wires that lead to your heart and provide it with electrical stimulation to prevent the heart from going too slow. You can't feel anything when the pacemaker is working but will be aware of a small flat lump under your skin just below your collar bone where the pacemaker is implanted.