Wolff-Parkinson-White Syndrome

Wolff-Parkinson-White Syndrome

Article Nov 29, 2009

Wolff-Parkinson-White (WPW) Syndrome is a potentially lethal abnormality within the heart’s conduction system that affects about 0.2% of the general population. About 70% of those with WPW have no history of cardiac disease. WPW is more common in men, and is most often diagnosed in children and young adults after they present to the ER with an arrhythmic event.

WPW is associated with an accessory pathway, usually the bundle of Kent, that is an extra lane of conduction between the atria and ventricles of the heart. This extra pathway is located in the myocardial wall and is faster than the normal lane of atrioventricular conduction due to the lack of an AV nodal pause. Many people with WPW may be asymptomatic their entire life. Most patients who do have symptoms present with a tachycardic emergency.

The AV node pauses normal conduction to allow for proper filling of the ventricles after atrial depolarization. Since the accessory pathway allows a faster lane of conduction, this can lead to premature ventricular depolarization, also known as pre-excitation,1 which can lead to what is known as a re-entry tachycardia.

The pause caused by the AV node can be depicted on an ECG as the PR segment, which starts at the end of atrial depolarization--the end of the P wave. The PR segment lies on the isoelectric line and ends at the start of the QRS complex. This segment becomes nearly nonexistent when WPW is present. Since the heart’s conduction bypasses the AV node by way of the accessory pathway, ventricular depolarization occurs directly after atrial depolarization. This inhibits maximum filling and cardiac output, according to Frank Starling’s law.

Because of the abnormal conduction of a heart with WPW, certain ECG findings may indicate this condition. In addition to a shortened PR segment, a delta wave may be present. This is a slurring upslope from the end of the P wave to the peak of the R wave that occurs due to the immediate ventricular depolarization following atrial depolarization.

Let's look at some examples of the way conduction might be altered in the presence of WPW. In the first example (Figure 1), an impulse is initiated in the SA node, then travels simultaneously down both the accessory pathway and the normal AV tract to the bundle of His. This causes the classic WPW presentation of a short PR segment and a delta wave.

The second example (Figure 2) shows what is called antidromic conduction.2 In this cycle, the impulse originates somewhere in the right atrium but conducts in a retrograde fashion through the accessory pathway and re-enters the atrium via the AV junction. This is an example of a re-entry tachycardia. This particular rhythm is called AVRT (atrioventricular reciprocating tachycardia), and is commonly misinterpreted as ventricular tachycardia due to its wide and fast appearance. Since the AV node is bypassed, atrial rhythms may be much faster than normal. A 3:1 atrial flutter can easily become a 1:1 atrial flutter at rates in excess of 300 bpm. These patients may need immediate intervention.

Figure 3 Conduction may also be orthodromic.3 Impulses may enter the ventricles in a normal physiologic manner, but they re-enter the atrium through the accessory pathway. The antegrade conduction may keep the QRS complex narrow, but the heart rate may accelerate due to a re-entry circuit. A bundle branch-like pattern may indicate this form of conduction.

Another possible presentation of WPW is FBI (fast, broad and irregular), which is specific for atrial fibrillation with WPW. By definition, this is a wide complex tachycardia (WCT). The American Heart Association (AHA) designed the WCT algorithm specifically for aberrancy like this. In the presence of WPW, traditional treatments may be contraindicated.

Continue Reading

Any AV nodal slowing agent, including adenosine, diltiazem and amiodarone, may cause an adverse reaction in the presence of WPW. Of those three medications, AHA recommends amiodarone. It is important to anticipate a lethal re-entry tachycardia with administration of any AV nodal slowing agent.4 Synchronized cardioversion is indicated for the unstable tachycardic patient.

It is important to keep WPW in mind when treating a tachycardia. The most benign treatment may be electrical therapy. Recognizing WPW may change your treatment strategy. Remaining keen to alternate patient presentations that may contraindicate traditional treatments is the practice of a good clinician.


1. Valderrama AL. Wolff-Parkinson-White syndrome: Essentials for the primary care nurse practitioner. J Amer Acad Nurse Prac 16(9):378-383, 2004.

2. Deam AG, Burton ME, Walter PF, Langberg JJ. Wide complex tachycardia due to automaticity in an accessory pathway. Pacing and Clinical Electrophysiology: PACE 18(11):2106-2108, 1995.

3. Kalarus Z, Kowalski O, et al. Electrophysiological features of orthodromic atrioventricular reentry tachycardia in patients with Wolff-Parkinson-White syndrome and atrial fibrillation. Pacing and Clinical Electrophysiology 26(7), Pt 1: 1479-1488, 2003.

4. Tijunelis MA, Herbert ME. Myth: Intravenous amiodarone is safe in patients with atrial fibrillation and Wolff-Parkinson-White syndrome in the emergency department. CJEM: Canadian Journal of Emergency Medical Care = JCMU: Journal Canadien De Soins Médicaux D'urgence 7(4):262-265, 2005.

Adam Thompson, EMT-P, is a paramedic with Lee County EMS in southwest Florida and an EMS educator with Edison State College. He is also creator of the multi-authored Web log paramedicine101.blogspot.com.

First responders in Mexico City were temporarily forced to pause search and rescue efforts in the wake of two massive earthquakes when residents experienced the third earthquake to occur in a matter of weeks.

California Urban Search and Rescue Task Force 6 brought 54 crew members to Puerto Rico to assist in search and rescue operations.
Emergency officials are telling residents to be patient while waiting for assistance because FEMA is stretched thin with three back-to-back hurricanes.
Join EMS leaders from around the country on October 5 for an interactive live discussion about how first responders can address the opioid epidemic.
The new contract will add an additional ambulance within the county, bringing the total to eight ambulances with the option to add additional ambulances if call volume increases.
You can help in an in-flight emergency, but here’s what to know.
Heavy traffic forces a childbirth in a familiar location.
The funds will be divided between the State Firefighter Association, the State Fire Marshal Association and the Assist the Officer Foundation of Houston in gratitude for their public service.
DMI announces the launch of EndZone, a cloud-based platform for mobile-centric situational awareness, delivering increased responsiveness and efficiency in emergency situations.
First responders are encouraged to link the website to their pages, as the service allows users to reconnect with loved ones in the aftermath of a natural disaster, such as Hurricane Maria.
The city of Twin Falls wants to place AED locations on its online public map after first responders informed officials of the importance of immediate AED use in a medical emergency.
First responders and legislators from Niagara County are saying too many areas are underserved and have to be covered by fire companies, calling for the need for additional ambulance services.
IV Tylenol, Motrin and Toradol will now be added to the options of ice and fentanyl for patient pain treatment during hospital transports to prevent opioid addiction.
Patients from the Caribbean islands in need of hospitals are being sent to South Carolina, where it's the first time the SCFC Incident Management Team has been activated for a disaster assistance response.

After the service at Burnette Chapel Church of Christ in Nashville, Tennessee had ended, a man wearing a ski mask drove up to the church and shot its attendees, killing one woman and injuring six others.