Wolff-Parkinson-White syndrome (WPW)
The heart beats on the command of an electrical signal, and that signal normally has one road to travel.
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Medicines commonly prescribed for Wolff-Parkinson-White syndrome (WPW)
For informational purposes only. Always consult a doctor before using any medicine.
Dosage form: CAPSULE, 100 mgActive substance: disopyramideManufacturer: Cheplapharm Arzneimittel GmbhPrescription requiredDosage form: INJECTABLE, 150 mg/3 mlActive substance: amiodaroneManufacturer: Sanofi Aventis S.A.Prescription requiredDosage form: TABLET, 200 mgActive substance: amiodaroneManufacturer: Aurovitas Spain, S.A.U.Prescription required
The heart beats on the command of an electrical signal, and that signal normally has one road to travel. In WPW syndrome it has two: alongside the normal route there is a spare bridge of muscle fibres that the person is born with. While the signal goes the way it should, nothing happens; but the moment it turns down the shortcut it starts running in a loop, and the heart races to two hundred beats a minute and beyond. For most people these are unpleasant but harmless episodes that a single procedure removes for good. There is one caveat, and it is worth reading on for: this particular syndrome has a rare scenario in which the spare pathway becomes genuinely dangerous.
Where the spare pathway comes from
Normally the atria and the ventricles are separated by a dense fibrous layer that carries no current, and the only door between them is the atrioventricular node. That node works like a turnstile: it holds the signal back, refuses to pass it on too often, and in doing so shields the ventricles from a runaway rhythm coming from above.
In WPW syndrome a thin strand of heart muscle has grown through that layer — the accessory pathway. It forms while the baby is developing before birth, and there is usually no reason behind it: it is not a consequence of anything the mother did, not a punishment, and not an acquired disease. Now and then families turn up with several affected relatives, but that is the exception.
The trouble with the accessory pathway is that it has no turnstile. The signal shoots along it in an instant, comes back through the node, sets off down the pathway again, and the loop closes. For as long as the loop turns, the heart contracts at its speed. That is the episode.
Two things are worth telling apart. Sometimes the pathway shows on the tracing but the person has never had an episode — that is called the WPW pattern, and the approach is calmer. Syndrome is the word used once episodes have been added to the picture on the trace.
What an episode feels like
The onset is always abrupt: not a heart winding itself up gradually out of nerves, but a switch being flicked. It stops just as suddenly. Between episodes the person feels ordinary and is in fact well.
During an episode there may be:
- a fast, regular, forceful heartbeat that can be heard in the ears and the throat;
- weakness, light-headedness, vision darkening on trying to stand up;
- breathlessness;
- pressure or pain in the chest;
- anxiety, trembling, cold sweat;
- an urge to pass urine shortly after the episode ends — a normal response of the stretched heart, and nothing to be alarmed by;
- less often, fainting.
It can last anything from a few seconds to several hours. Some people get an episode once every few years, others several times a week; the frequency cannot be predicted in advance. Most begin of their own accord, though a sudden effort, strong coffee, a lot of alcohol, a short night or bending forward can set one off.
A separate word about children: a baby will not complain, and an episode shows itself as refusing feeds, pallor, listlessness and fast breathing. If that keeps happening, the thing to tell the doctor is precisely that it keeps happening.
Why the syndrome is not left unwatched
The episodes described above are not, in themselves, life-threatening. The danger lies in a different combination, and it is rare but real.
If someone with an accessory pathway goes into atrial fibrillation — the chaotic quivering of the atria at several hundred impulses a minute — the atrioventricular node holds back most of that torrent, as it is designed to. The accessory pathway holds back nothing. It can let the chaos straight through to the ventricles, which then contract so fast and so disorderedly that they stop pumping blood. This is a life-threatening state and needs immediate help.
It does not happen often, and the great majority of people with this syndrome grow old without any drama at all. But it is because of this scenario that the syndrome is not left unattended even when episodes are infrequent and easily tolerated: the risk depends not on how often you feel unwell, but on the properties of the pathway itself. Only a doctor can judge those properties — from the tracing, from how the pre-excitation signs behave under exertion and, if needed, from a study carried out inside the heart.
When to call an ambulance, and what to try before it arrives
Call an ambulance (112 is the single European number; your country may have its own) if any of the following appears during an episode:
- pain or heavy pressure in the chest;
- marked breathlessness, air hunger at rest;
- fainting, or feeling that you are about to pass out;
- the heartbeat stops being regular and turns ragged and disordered;
- the episode does not settle on its own and does not respond to the manoeuvres you have been taught;
- the skin turns pale and clammy and the person is drowsy and hard to rouse.
In these situations there is no point waiting to see whether it passes, and nobody drives in that state. If it was your first episode, see a doctor whatever happens, even if the whole thing lasted a minute and you now feel perfectly fine: between episodes the tracing can look deceptively calm, and capturing the rhythm matters.
There are manoeuvres that irritate the vagus nerve and can break the loop: straining with the mouth shut and the nose pinched, putting the face in cold water, coughing. In people who already have the diagnosis they often work. But they are not to be picked up from a description on the internet — which one suits you, how long to hold it and when it must not be done is something a doctor shows you. Massaging the neck is not on this list: it is not done unsupervised.
How it is picked up
The main tool is an ordinary electrocardiogram. The accessory pathway leaves a characteristic mark on it: the ventricles start to be activated a fraction early, and the rise of the trace becomes sloped, with a smudged beginning. An experienced eye recognises the picture at once, and the syndrome is often found by chance on a tracing taken before an operation or at a routine check.
The difficulty is that the pathway is not always visible: it can conduct intermittently, and then a tracing taken on a quiet day looks normal. Hence the use of:
- monitoring over a day or several days, with a device worn on the body that records the rhythm continuously;
- an event recorder switched on by the patient when an episode starts — handy when episodes are rare;
- an exercise test: if the pre-excitation signs vanish at a high heart rate, that argues for a pathway that conducts sluggishly;
- an echocardiogram, to look at the structure of the heart, because occasionally the syndrome sits alongside a congenital defect;
- an electrophysiological study: fine electrodes are passed into the heart through a vessel, the pathway is pinpointed and its conduction speed measured. That same study is usually combined with treatment.
Ablation is the routine answer, not a last resort
Catheter ablation removes the cause: the accessory pathway is located from inside the heart and destroyed at a single spot with heat or cold. Access is through a vessel in the groin, the chest is not opened, the anaesthetic is usually not a general one, and people normally go home the next day.
Three things are worth knowing about it:
- it cures the great majority — success is measured at figures of the order of ninety-five per cent, and after a successful procedure the episodes do not come back and the pathway stops being a threat;
- it is not the final barricade reached after everything else has been tried. Nowadays it is often offered straight away instead of years of tablets, particularly to young people, to those whose work carries responsibility for others, and to those whose pathway has worrying properties;
- the risk of complications is low but not nil, and it is higher when the pathway sits close to the normal conducting system. That is discussed before the procedure.
Medicines are used too — when ablation is unsuitable, is being postponed, or the person declines it. They are chosen only by a heart rhythm specialist, and that is what the next section is about, because there is a catch here.
What your doctors must always be told
This is the most practical part of the page. Some of the drugs used in ordinary life to slow the pulse and treat arrhythmias can do harm in WPW syndrome. The mechanism is simple: they hold the signal back at the atrioventricular node — that turnstile — and in doing so clear the road for the accessory pathway. If atrial fibrillation happens at that moment, the whole torrent goes round the shortcut and things get worse rather than better. Cardiac glycosides and some rate-slowing calcium antagonists belong to this group, and a number of other agents are used with caution. The names matter less than the rule.
The rule is this: if you have been diagnosed with WPW, name the diagnosis to every doctor who prescribes for you — your family doctor, a surgeon, the anaesthetist before an operation, the dentist, the ambulance crew. Carry the report with you, or a note on your phone. And do not take anything "for palpitations" that helped an acquaintance or was left over from an old prescription: what is safe in an ordinary tachycardia does the opposite when there is an accessory pathway.
After a successful ablation this restriction is lifted, and the doctor will tell you so plainly.
Online consultation
A remote appointment is a good place to sort out what usually stays unclear. A doctor can help you read the report on your tracing and explain whether this is a pattern or a syndrome; work out whether your episodes look like an accessory pathway tachycardia or like something else; and say which test makes sense next and how urgently. It is also a convenient way to weigh up whether ablation is worth having and what it would change, to check that the medicines you have been prescribed sit safely with the diagnosis, and to settle questions about sport, pregnancy and work. An episode happening right now is not treated online — with any of the signs listed above, call an ambulance.
This material is for information only and does not replace medical advice.
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