The normal rhythm of the heart is called sinus rhythm. Abnormal rhythms are referred to as arrhythmias.
In order for the heart to pump blood around the body, it needs electrical impulses.
These impulses start at the top of the heart (at the sino-atrial node) and trigger the top chambers of the heart (the atria) to contract, forcing blood into the lower chambers (the ventricles). The impulse then reaches the full ventricles, causing the right one to pump blood to the lungs to receive oxygen, and the left one pumps oxygen rich blood around the body.
The electrical rhythm of the heart can be recorded and interpreted by an ECG (electrocardiogram). The normal resting heart rate for a healthy adult is 60-100 beats per minute. However, it is perfectly normal for our heart rate to fluctuate throughout the day, generally being lower at rest, and higher during light activity. When we exercise, our heart rate increases to meet the oxygen demands of body, particularly our muscles.
Palpitations are a common and usually normal sensation of being able to feel your own heartbeat and most people will experience these at some time, for example in times of confrontation you may feel your heart ‘pound’. However, frequent or persistent episodes of palpitations should be investigated to ensure your heart is healthy and there is no underlying cause.
People may also experience something called an ectopic beat which is the feeling that your heart has given an extra beat, or even skipped a beat. These are normally harmless and do not indicate a cardiac problem, however, if you are concerned you should consult your GP for advice.
There are several abnormal rhythms that can be produced by the heart but there are two main groups of arrhythmias:
- Supraventricular arrhythmias (abnormal rhythm starts above the ventricles)
- Ventricular arrhythmias (start in the ventricles)Arrhythmias can not only cause irregular heart rates, but also cause either a slow heart rate, known as bradycardia, or a fast heart rate, known as a tachycardia.
One of the most common arrhythmias is atrial fibrillation, a supraventricular arrhythmia, which is when the electrical impulses are not fired from the normal place in the heart and are released in a disorganised manner. This causes the top chambers of the heart (the atria) to contract irregularly, and often so quick that the muscles are not given enough time to relax (and re-fill with blood). The result is that the heart may not work as efficiently as it should.
Atrial fibrillation can be felt as an irregular and sometimes fast pulse and requires investigation to find out the cause. AF is a serious arrhythmia and can lead to suffering a stroke, and can be commonly associated with coronary heart disease.
The cause of AF is not fully understood, however the commonly known conditions that can lead to developing AF include:
- high blood pressure
- heart valve disease
- congenital heart disease
AF can be triggered by certain factors:
- excess alcohol
- excessive intake of caffeine (tea, coffee & energy drinks)
- being overweight
- taking illegal drugs – such as amphetamines or cocaine
The most obvious symptom of AF is an irregular pulse, but you may also experience dizziness, shortness of breath, fatigue and chest pain. People with atrial fibrillation may experience no symptoms, however, and the condition is discovered during GP checks or investigations for another condition.
Atrial fibrillation on its own is generally not life –threatening, although you may feel uncomfortable at times. Treatment depends on several factors, but is generally aimed at controlling the abnormal rhythm with medications, preventing strokes, and improving lifestyle.
For more information on arrhythmias, please refer to:
The British Heart Foundation