Wolff–Parkinson–White syndrome

Introduction•Wolff–Parkinson–White syndrome (WPW) a pre-

excitation syndrome is caused by the presence of an abnormal accessory electrical conduction pathway between the atria and the ventricles.

• This is often congenital

Signs and Symptoms • People with WPW are usually asymptomatic. However, the

individual may experience

• palpitations,

• dizziness,

• shortness of breath,

• syncope

• sweating

Pathophysiology

•…and as it gets to the Purkinje fibers, next is the endocardium at the apex of the heart, then

finally to the ventricular myocardium.

Atrioventricular node.

The AV node serves an important function

• limiting the electrical activity that reaches the ventricles.

• it slows down individual electrical impulses. (the PR interval)

However….• Individuals with WPW have an accessory pathway that

communicates between the atria and the ventricles, in addition to the AV node. This pathway forms a bypass which enables supraventricular impulse to bypass AV node , bundle of HIS and distal conducting system and so activate or pre excite the ventricles. An Individual could have more than one accessory pathway.

• The most common accessory pathway is known as the Bundle of Kent

• This accessory pathway does not share the rate-slowing properties of the AV node, and may conduct electrical activity at a significantly higher rate than the AV node.

…with Bundle of Kent

This pathway may communicate between

the left atrium and the left ventricle, in which case it is termed a "type A pre-excitation"

or the right atrium and the right ventricle, in which case it is termed a "type B pre-pre-excitation".

Problems arise when this pathway creates an electrical circuit that bypasses the AV node. When an aberrant electrical connection is made via the bundle of Kent, tachydysrhythmias may therefore result.

ECG Presentation

• Short PR interval

• Slurred initial upstroke of QRS – delta wave

•Relatively normal , narrow terminal QRS –main QRS deflection

• Slight widening of QRS

• Secondary STT changes

Phases of Cardiac ActivationPHASE 1

• Atrial activation- normal

PHASE 2

• Ventricular pre-excitation

• sinus activation occurs through both normal , anomalous pathway

• anomalous pathway lacks AV nodal conduction delay

• so sinus impulse conducted at a rapid rate

• this enables ventricles to be activated or pre exited- short PR interval , delta wave

• Further activation through normal pathway

PHASE 3

• Narrow terminal QRS

PATHWAY

ORTHODROMIC

• DESCEND- NORMAL PATHWAY

• ASCEND- ACCESSORY PATHWAY

• In orthodromic tachycardia, the normal pathway is used for ventricular depolarization and the accessory tract is used for reentry.

• Ventricular Premature Contractions can initiate orthodromic tachycardia

• On ECG findings, • the delta wave is absent, • QRS complex is normal, • P waves are inverted in the inferior and lateral leads

ANTIDROMIC

• LESS COMMON PATHWAY.

• DESCEND- ACCESSORY PATHWAY.

• ASCEND – NORMAL PATHWAY

• On ECG findings, • the QRS is wide, which is an exaggeration of the delta wave during sinus

rhythm (i.e, wide-QRS tachycardia).

• Such tachycardias are difficult to differentiate from ventricular tachycardia

The ‘accessory’ conduction pathway fibers

Other than the Kent Fibers (Atrio-Ventricular) previously discussed…

MAHAIM FIBRE:

• Origin- distal to AV node (Hiso-Ventricular)

• Ends in the ventricular myocardium

ECG:

• normal PR interval

• delta waves

JAMES FIBRE (LGL SYNDROME)

• Origin- atria (Atrio- His)

• Bypass AV node

• Ends in bundle of HIS

ECG:

• Short PR

• Normal QRS (AV node function is still retained)

Complications• Tachyarrhythmia

• Syncopal attacks

• Sudden cardiac death

• Complications of drug therapy (eg, proarrhythmia, organ toxicity)

• Complications associated with invasive procedures and surgery

• Recurrence

Treatment

• People with atrial fibrillation and rapid ventricular response are often treated with procainamide or amiodarone (rarely). This is to stabilize their heart rate

• The definitive treatment of WPW is a destruction of the abnormal electrical pathway by radiofrequency catheter ablation.

Caution should be taken in regards to…• Possibility of Sudden Cardiac death

• AV node blockers should be avoided in atrial fibrillation and atrial flutter with WPW or history of it; this includes adenosine, digoxin, diltiazem, verapamil, other calcium channel blockers and beta blockers. They can exacerbate the syndrome by blocking the heart's normal electrical pathway

• Underlying Ebstein’s anomaly, hypertrophic cardiomyopathy should be evaluated (In cases of more than one accessory pathway)

I appreciate your attention.Adighibenma S.O.S