Premature atrial contractions: skipped beats explained

The heartbeat is set off by an electrical signal that normally starts in a small area at the top of the right atrium. Occasionally another spot in the atria fires early, before the next regular signal is due. The result is a premature atrial contraction, usually shortened to PAC. The early beat often fills the heart with less blood than usual, so it is barely felt, and the pause that follows lets the next regular beat fill the chambers more fully and land harder. That harder beat, rather than the early one, is often what people describe as a thump or a flip in the chest.

PACs belong to the group of beats known as ectopic beats. The NHS describes palpitations as a heartbeat that feels racing, irregular with skipped or extra beats (ectopic beats), pounding or fluttering, and says they can last seconds, minutes or longer. NICE Clinical Knowledge Summaries lists supraventricular and ventricular extrasystoles among the arrhythmias that can cause palpitations, alongside tachycardias, atrial fibrillation and atrial flutter. A PAC is therefore one small piece of a wider picture, and the reason for a proper assessment is to make sure it is only that.

Sensation varies enormously. Some people with hundreds of PACs a day feel nothing, and the beats only come to light on an ECG or fitness-tracker alert taken for another reason. Others are acutely aware of a single early beat. Awareness tends to rise when you are lying still at night, after a large meal, when you are anxious, or when you are tired, because there is less to distract attention from the chest.

The British Heart Foundation describes palpitations as the feeling that the heart is racing, pounding, fluttering or has missed beats, felt in the chest, neck or throat, and notes they can happen at any time, even at rest. It also points out that they often feel more serious than they are. That is reassuring, but it does not remove the need to look at the whole picture: how often they happen, whether they come on with exertion, and whether anything else accompanies them.

• A brief flutter or a sense that the heart stopped for a moment.

• A single hard thump, often just after a pause.

• Short runs of fast beating that settle on their own.

• No symptoms, with the beats discovered on a routine pulse check or tracing.

The NHS lists strenuous exercise, lack of sleep, stress and anxiety, some medicines, and alcohol, caffeine, nicotine and recreational drugs as common causes of heart palpitations. It adds that menopause and pregnancy can bring them on, and that they can be linked to iron deficiency anaemia, an overactive thyroid, a heart rhythm problem or other heart problems such as valve disease. The British Heart Foundation adds smoking or vaping, triggering foods such as spicy or rich meals, and over-the-counter medicines to the list.

Because triggers differ between people, a symptom diary is the most practical tool. Noting the time, what you had eaten or drunk, how you slept and what you were doing often reveals a pattern that a single appointment cannot. The same diary helps a clinician decide whether blood tests, a thyroid check or a longer monitor would be useful.

The first test is usually a 12-lead electrocardiogram. Small sticky pads on the skin record the electrical signals of the heart over a few minutes. NICE Clinical Knowledge Summaries advise arranging it ideally during an episode of palpitations, because a trace taken when you feel fine is often normal. If the beats come and go, the next step is an ambulatory ECG, a small portable recorder worn for days or weeks, which is the reason a routine cardiology referral may be made for palpitations of uncertain cause.

Other checks depend on the story. Blood tests can look for causes such as anaemia or thyroid overactivity. An echocardiogram, an ultrasound scan of the heart, is arranged if a murmur, heart failure or structural heart disease is suspected. The aim is to separate the common benign picture from the smaller number of people whose beats sit on top of a heart muscle, valve or rhythm problem that deserves its own treatment.

The NHS advises seeing a GP if palpitations keep coming back or are happening more often, last longer than a few minutes, or occur in someone who has a heart condition or a family history of heart problems. It advises calling 999 or going to A&E if palpitations are happening now and will not go away, or if they come with chest pain, shortness of breath, or feeling faint or fainting. If those symptoms have stopped, it suggests asking the surgery for an urgent appointment or contacting NHS 111.

NICE Clinical Knowledge Summaries lists the features that move a person towards urgent cardiology assessment: palpitations with associated symptoms, palpitations triggered by exercise, and a family history of sudden cardiac death under the age of 40 or of hypertrophic cardiomyopathy. These are the situations where the early beat could be a clue to something else, which is why they are separated from the ordinary, reassuring pattern.

When the ECG and examination show nothing concerning, the standard approach is reassurance and attention to triggers. The NHS says treatment depends on the cause and that palpitations often need no treatment; avoiding triggers such as stress, smoking, caffeine and alcohol can help when no health condition is responsible. The British Heart Foundation gives a sensible alcohol ceiling of no more than 14 units a week and suggests cutting back caffeinated drinks and managing stress.

Medicines are reserved for troublesome symptoms or an underlying rhythm disorder. The British Heart Foundation gives beta blockers as an example of a drug a doctor might prescribe to control heart rate and rhythm in a person diagnosed with an arrhythmia. People who have been told their PACs are harmless often find the fear of them fades faster than the beats themselves; asking for the explanation to be written down can help.

• Keep a symptom diary for a few weeks and bring it to the appointment.

• Try cutting caffeine and alcohol for a short period to see whether the pattern changes.

• Review the leaflets of any regular or over-the-counter medicines with a pharmacist.

• Do not ignore chest pain, breathlessness or fainting, however familiar the beats feel.