Wolff-Parkinson-White Syndrome

Wolff Parkinson White syndrome is an unusual heart rhythm condition in which patients can develop sudden onset of fast heart palpitations. These can be associated with light-headedness/dizziness, blackouts, chest pain and in very rare cases, sudden death. However the good news is that this is a completely curable condition.

Wolff –Parkinson-White syndrome was first described by 3 physicians – Louise Wolff, Sir John Parkinson and Paul Dudley White who described 11 patients who had and abnormal resting ECG and who developed intermittent sudden episodes of fast heart rate. There were 3 main ECG abnormalities seen.

Firstly: the PR interval was short

Secondly: the QRS was abnormally wide

Thirdly: they had something called a Delta wave which was an unusually slurred upstroke to the QRS segment.

The fundamental problem in patients with this condition is that they have an extra electrical pathway in their heart.

Let me explain. In the normal heart, the top chambers of the heart (the atria) and the bottom chambers of the heart (the ventricles) are electrically isolated. So normally what happens is that an impulse is generated in the sino-atrial node (the pacemaker of our heart that god gives us when we are born). The impulse can only travel to the ventricle via an electrical pathway known as the His-Purkinje system. To get to the His Purkinje system, the impulse has to go through the AV node which can be likened to a toll booth and the AV node ensures that the impulses don’t go through too quickly. Once the impulse gets to the ventricles, it causes the ventricles to contract. Patients with WPW however have another electrical pathway too and usually as there is no AV node, these pathways conduct electricity much quicker that the normal.  These extra pathways are called accessory pathways and the problem is that they can therefore provide a short-circuting mechanism by which an impulse could go either down the AV node and then back up through the accessory pathway or down the accessory pathway and up through the his-purkinje system thereby causing a very rapid heart rate which can then be manifest in the patient as a sudden onset of very fast palpitations

One other thing to be aware of is that not all accessory pathways are the same. The majority (60-75%) of accessory pathways are capable of bi-directional conduction which means that they can allow impulses to go down them and up them.  About 17-37% allow only impulses to go up them but not down them and 5-27% will only allow impulses to go down them but not up them.

So if you have a pathway which allows impulses to go down it or in both directions, you can get a clue on the ECG. As the pathway conducts faster, the PR interval is shorter and because the pathway is on one side the conduction acorss the ventricle takes longer and therefore the QRS looks wider and you see a delta wave. This ECG pattern is called Pre-excitation or WPW pattern.

However if you have a pathway that only allows retrograde conduction, the impulses would still go down the right way and therefore the ECG will look normal and the first time you will know about the extra pathway is when the short circuiting takes place i.e when the palpitations happen. This is why these pathways are called ‘concealed pathways’.

I think it is important to understand the difference between Wolff-Parkinson-White pattern which is purely what you see on an ECG and Wolff-Parkinson-White syndrome which is when you have the ECG abnormalities in a patient who is suffering recurrent palpitations due to the extra pathway.

1-2 people in a thousand have WPW pattern.

The prevalence is higher in 1st degree realtives suggesting that there may be a familial component – 3.4%

The WPW pattern may be intermittent and may even disappear permanently over time. Intermittent WPW pattern is seen in 10-40% of patients.

Intermittent WPW pattern actually indicates that the accessory pathway may not be a particularly fast pathway and therefore can get even slower with age and thereby disappear.

Only 1-2% of these actually have WPW syndrome i.e. suffer the consequences of having the extra pathway by manifesting with a heart rhythm disturbances.

Even in these patients, the risk of sudden death is exceedingly rare (1/1000). One of the reasons for this is that patients with WPW often do not have any other coexisting heart disease

Diagnosis

Usually made by doing a simple ECG which may show pre-excitation – but as I have said before if the pathway is concealed the ECG may be normal. In these patients the only way to be sure is by doing electrophysiological studies.

Exercise testing can sometimes be helpful because if on exercise the ECG changes normalise it means that the extra pathway is unable to conduct impulses at a very fast rate and therefore it is less likely that they will develop extremely fast heart rates.

 

Treatment

In patients who have a typical ECG and are having typical heart rhythm disturbances, treatment is straightforward, They should see an electrophysiologist and be considered for an ablation because this offers a permanent cure.

The bigger problem is in those patients who have an abnormal ECG but have never had any palpitations. Most of these patients will remain asymptomatic. Up to 20% may develop symptoms over the next 3 years.  Generally as long as patient have a structurally normal heart and no symptoms then they can generally be reassured. In those patients who have WPW pattern, there is obviously a worry about this risk of sudden death but virtually all the cases of sudden cardiac arrest will have had palpitations before hand so if you have never had fast sustained palps then the risk is extremely low. If further reassurance is needed then an exercise test can be very helpful because if at fast heart rates, the ecg pattern disappears then it is unlikely that the extra pathway will conduct very fast heart rates and therefore this is a good sign.

If the ecg pattern doesn’t disappear then patients may benefit from electrophysiological studies.

 

In summary, it is very important to understand the difference between WPW pattern and WPW syndrome. Most patients with WPW pattern will remain asymptomatic. If you have had had recurrent sustained palpitations and have WPW pattern on your ECG then it is likely that you have WPW syndrome and in this setting, you should definitely see an electrophysiologist and consider an ablation which will usually be curative.

Here is a link to a video, I have done on this subject:

https://youtu.be/pqZ3Bdqf7W4

About the Author:

Dr Sanjay Gupta
I'm Dr Sanjay Gupta, a Consultant Cardiologist with specialist interest in Cardiac Imaging at York Teaching Hospital in York, UK. I believe that high quality reliable jargon-free information about health should be available at no cost to everyone in the world.

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