What exactly is an arrhythmia?

The word arrhythmia comes from two greek words. The first is ‘a-’ which means absence or loss and the second is ‘rhythmos’ which means rhythm. So arrhythmia literally means absence or loss of rhythm. A cardiac arrhythmia therefore means loss of cardiac rhythm. It is however used in medical practice as a description for disturbance rather than absence of heart rhythm. In that sense the term dysrhythmia is preferable because it does literally translate as a disturbance in normal rhythm which is exactly what it is meant to describe.
The heart is a pump and its role is to work as efficiently as possible to try and get oxygen rich blood round to all the vital organs of the body. It works most efficiently by beating in a regular rhythm and at a certain speed. Any unsolicited disturbance of the rate or rhythm can be termed a dysrhythmia and result in the heart beating less efficiently only for the duration of the dysrhythmia. Sometimes the inefficiency may be so trivial or short-lived that the patient feels no symptoms at all. Sometimes the inefficiency can be so significant or sustained that the patient feels symptoms or can even be incapacitated. It is important that the term dysrhythmia is never enough as a complete diagnosis. Dysrhythmia is an umbrella term for any kind of electrical disturbance rather than pinpointing the exact diagnosis.
In terms of symptoms, the most common symptom of a dysrhythmia is heart palpitation. A heart palpitation is an awareness of the heart beating in a way that feels abnormal to the patient. This may feel as an unusually fast heart beat or an unusually slow heart beat or a skipping, banging, racing or fluttering sensation in the chest. It is important to know that not all dysrhythmias cause palpitations and neither are all palpitations due to a dysrhythmia. Palpitations are a symptom that the patient experiences and a dysrhythmia is a diagnosis usually made on an ECG recording of the heart.
Depending on how inefficient the heart becomes during the dysrhythmia, other symptoms may also become manifest. These include breathlessness, chest pain, dizziness or even blackouts.
The diagnosis of a dysrhythmia is made by recording an ECG during the dysrhythmia. As dysrhythmias are often paroxysmal, meaning that they can come and go, an ECG done in the absence of the dysrhythmia may be normal and therefore mislead the patient into thinking that there is no dysrhythmia present. This is why the most reliable way to diagnose a dysrhythmia is to do an ECG during the symptoms. In those patients who are asymptomatic, the only way to pick up a dysrhythmia is to do prolonged and continuous ECG monitoring. Perhaps the most useful monitor in this regard is a REVEAL device which is a small cigarette lighter sized device which can be easily inserted under the skin and can monitor the heart for any rhythm disturbances for up to two years.
Definitive treatment of a dysrhythmia is only possible after it has been caught on an ECG. The good news is that catching it on an ECG will allow the doctor to characterise it further and give it a name. This is very important because different heart rhythm disturbances can disturb the heart efficiency in different ways and therefore pose different risks to the patient.
In particular, sustained dysrhythmias which go on persistently for minutes or several hours are more likely to cause symptoms or even harm compared to transient dysrhythmias. Secondly, dysrhythmias which are accompanied with the heart going excessively fast or excessively slow are again more likely to be more serious. Finally dysrhythmias which originate in the ventricles of the heart are more likely to be more inefficient and thereby more dangerous than those that arise from the atria or from above the ventricles.
There are two other important points to note. Dysrhythmias are more likely in patients who are older and sicker with a larger burden of comorbidities such as diabetes, high blood pressure, sleep apnoea and vascular disease. Dysrhythmias are also more likely to be less benign in such patients compared to patients who are young and otherwise completely well.
The second point is that if the heart is damaged for some reason then it is already inefficient and irritable. Therefore damaged hearts are more likely to be prone to dysrhtyhmias and are likely to tolerate sustained dysrhythmias poorly and this is why everyone with a sustained dysrhythmia should have an echocardiogram and ideally some evaluation of the heart arteries which supply blood to the heart. If we know that the heart as a pump is strong and the blood supply to the pump at times of stress is good then the heart will cope with even very fast heart rhythm disturbances. The patient may still feel unwell with them but the heart will cope well enough to give the patient enough time to go to a hospital to get it treated.