What are palpitations?
The term palpitation simply means an awareness of the heartbeat. The majority of palpitations are a nuisance rather than a danger. Although they can be unpleasant, they are usually quite harmless. The heart may be beating at a normal rate, slowly, fast, erratically or just missing beats. Abnormal heartbeats are called arrhythmias. On occasions they may indicate problems with the heart muscle, valves or arteries.
The heartbeat is triggered by an electrical impulse that starts in the sinus node – the heart’s natural pacemaker. Normally the sinus node delivers electrical impulses at a rate of 60–100 beats per minute; this is called sinus rhythm. The optimum heart rate is determined by the sinus node, which responds to your needs, causing the heart to beat faster during exertion and slower when resting.
A heart rhythm that is fast is called a tachycardia; one beating too slow is called a bradycardia. If the arrhythmia starts in the upper chambers of the heart it is called a supraventricular arrhythmia. For example, if a fast rhythm starts from the upper chamber it would be called a supraventricular tachycardia. If the abnormal beats originate from the lower chambers they are called ventricular arrhythmias.
Heartbeats that are too fast or too slow can be associated with symptoms such as:
- Chest pain
What causes palpitations?
Each beat of the heart is triggered by an electrical impulse from the heart’s natural pacemaker, the sinus node. The electrical wave passes through the atria to the atrioventricular node (the AV node). From here it spreads rapidly through the heart’s lower chambers, the ventricles.
Arrhythmias (disturbances of the heart rhythm) may occur due to:
- Abnormal functioning of the cells carrying the electrical impulse.
- Damage to the heart muscle.
- Heart defects, including valve disorders.
- Conditions where there are abnormal electrical connections or pathways between the upper and lower chambers of the heart, for example Wolff–Parkinson-White syndrome.
- Side-effects of certain medications.
- Overactive thyroid or adrenal glands producing excessive hormone levels.
Other common causes of palpitations include:
There are many different types of arrhythmia:
- Extrasytoles or ectopic beats are extra beats and are very common. They may come from the upper chambers when they are called atrial ectopics, or from the lower chambers, when they are termed ventricular ectopics. They can be recognised as differing from the normal heartbeat and can therefore cause concern. However, these do not damage the heart and are not dangerous.
- Sinus tachycardia is a normal speeding up of the heartbeat in response to stress or exercise.
- Sick sinus syndrome is a condition in which the sinus node does not fire often enough, resulting in the heart rate being too slow. It can also be associated with periods of rapid heartbeats.
- Supraventricular tachycardia, also known as SVT, is caused by rapid but regular electrical activity in the upper chambers of the heart.
- Atrial flutter is a form of supraventricular tachycardia. The upper chambers of the heart beat regularly but very fast.
- Atrial fibrillation, also known as AF, is the result of rapid and irregular electrical activity in the atria that causes the ventricles to contract irregularly.
- Ventricular tachycardia is a condition in which the larger chambers of the heart beat fast but the rate in the upper chambers remains normal. It occurs usually as a complication of heart disease and can be dangerous if untreated, leading to blackouts.
- Ventricular fibrillation results from very fast, erratic and uncontrollable electrical signals in the ventricles. This is potentially a very dangerous rhythm as it causes the heart to quiver rather than beat, invariably leading to blackouts within seconds.