Atrial fibrillation

Atrial fibrillation is the commonest lasting disturbance of heart rhythm. The upper chambers of the heart stop contracting together and merely quiver, so the pulse becomes uneven and often fast as well. On its own it rarely threatens life in the first minutes, yet this particular arrhythmia is behind a large share of severe strokes — and those are exactly what can be prevented.

Why the beat loses its rhythm

In a healthy heart the timing is set by a small patch in the right atrium, and the impulse travels downwards in even waves. In fibrillation hundreds of small impulses race chaotically across the atria: no coordinated squeeze happens, blood pools, and only a random share of those impulses reaches the ventricles. That is where the ragged pulse comes from.

The arrhythmia is grouped by how it behaves. The paroxysmal kind stops by itself, usually within a day or a few days. The persistent kind does not stop on its own: the rhythm has to be brought back with drugs or with a shock. It is called permanent once doctor and patient have agreed to stop trying to restore the rhythm. Over the years one form tends to turn into another.

People feel it very differently. The heart may pound or seem to stumble, breath runs short on an ordinary walk, unusual tiredness sets in, the head swims, the chest feels tight. Yet a sizeable number of people notice nothing at all, and the arrhythmia turns up by chance on a tracing taken before surgery or at a check-up. Feeling nothing does not mean the risk is any lower.

The pulse is easy to check yourself: two fingers on the wrist on the thumb side, counting beats for a full minute. In fibrillation the gaps between beats are of different lengths and the strength of each beat jumps about.

The real danger is a clot, not the palpitations

When the atria quiver instead of contracting, blood stagnates in a small pouch of the left atrium. A clot forms there and one day the bloodstream carries it into the vessels of the brain. Strokes of this kind are on average more severe and more often leave lasting disability.

The key point: the risk of a clot has nothing to do with how strongly the arrhythmia is felt. With short, occasional episodes it can be the same as with the permanent form. It is worked out from age, sex, blood pressure, diabetes, heart failure, vascular disease and any previous stroke.

Where that risk is appreciable, the doctor prescribes anticoagulants — medicines that make the blood clot less readily. Ordinary aspirin does not give this protection and cannot stand in for them. Missed doses matter, because the cover disappears quickly. Bruises with no cause, blood in the urine or stool, prolonged bleeding from the nose or gums are all reasons to contact the doctor promptly rather than quietly stop the tablets.

What sets an episode off

• raised blood pressure, the commonest soil for this arrhythmia;
• heart failure, a previous heart attack, damaged valves;
• excess weight, which loads the atria;
• pauses in breathing during sleep, especially with loud snoring;
• alcohol, including a single heavy session in an otherwise healthy person;
• an overactive thyroid gland;
• diabetes, chronic kidney disease, smoking;
• years of endurance training: marathons, long cycle rides, cross-country skiing;
• acute illness such as pneumonia, severe infection, surgery or dehydration, where the rhythm often settles once the person recovers.

Two causes deserve to be singled out. The first is an excess of thyroid hormone: the arrhythmia can be its only sign, and once the thyroid is treated the rhythm may return on its own, which is why a thyroid-stimulating hormone test is done for everyone newly diagnosed. The second is a rare inborn quirk of the conducting pathways, ventricular pre-excitation syndrome. It shows up in young people, and with it some of the usual rate-slowing drugs are not merely useless but dangerous: the rhythm can speed up to threatening levels. That is why the tracing of a young person is read with particular care.

Signs that mean calling an ambulance

• crushing or burning chest pain, all the more so with sweating and nausea;
• a drooping face, weakness in an arm or leg on one side, slurred speech, sudden loss of vision — even if it has already passed;
• fainting, or the feeling that a faint is coming;
• severe breathlessness, being unable to lie flat, bubbling breathing;
• a very fast pulse that will not slow, along with pallor, cold sweat and weakness;
• a first-ever episode, if it lasts more than a day or is hard to bear.

Call your local emergency number (112 in much of Europe). Nobody should drive in that state.

How the diagnosis is made

Only an electrocardiogram recorded during the arrhythmia can make the diagnosis. That is the difficulty: the episode often ends on the way to the clinic and the ordinary tracing comes back normal.

So when episodes are occasional, monitoring over a day or over several days is used, and when they are very rare, a recorder that the patient switches on personally. Smartwatches and portable sensors are sometimes the first to spot an uneven rhythm, but their trace is a reason to have a proper electrocardiogram, not a diagnosis in itself.

An ultrasound scan of the heart is added: chamber sizes, valves, pumping function. The useful blood tests are thyroid-stimulating hormone, haemoglobin, potassium, magnesium, kidney function and glucose (measured in mmol/L), because they change which drugs can be used.

What treatment can and cannot do

Treatment runs along two independent tracks, and neither replaces the other.

The first is protection against clots: anticoagulants, and where these are ruled out because of bleeding, closing off that same pouch of the atrium with a device is discussed.

The second is work on the rhythm itself, and here there are two routes. The rhythm can be left as it is while the rate is held within sensible limits, using beta blockers, certain calcium channel blockers and sometimes cardiac glycosides. Or the correct rhythm can be restored and maintained with antiarrhythmic drugs, with a shock under brief anaesthesia, or with catheter ablation, in which the areas sending out the surplus impulses are treated spot by spot from inside the heart. Ablation works better in the paroxysmal form and when the atria are not much enlarged.

A separate job is to remove whatever feeds the arrhythmia: bring the blood pressure down, correct the thyroid, treat sleep apnoea and heart failure. Without that the episodes come back, whatever is done to the rhythm.

No method can promise that the arrhythmia will never return. The aim is different: to take away the symptoms, restore tolerance of exertion, and lower the chance of a stroke.

What is in your hands day to day

• lose weight if there is excess: episodes become noticeably less frequent;
• give up alcohol or cut it to a minimum — the effect shows within the first months;
• have sleep breathing checked if there is loud snoring with pauses, and treat apnoea if it is confirmed;
• keep blood pressure under control and measure it at home;
• stay active regularly and moderately, without punishing training or marathons;
• never stop the anticoagulant on your own and do not skip doses;
• tell every doctor and the dentist that you are taking an anticoagulant;
• check new medicines and supplements with your doctor: painkillers, some antibiotics and herbal remedies alter how they work.

Online consultation

In an online appointment a doctor can go through how the episodes run and what brings them on, look at electrocardiograms and blood results you already have, say which investigations should come next, explain the point of the prescribed regimen and the rules for taking an anticoagulant, and advise when a face-to-face visit to a cardiologist is needed.

This material is for information only and does not replace medical advice.