October 05, 2010

Q&A: Diagnosis of Wolff-Parkinson-White Syndrome

Louis Wolff, Sir John Parkinson, and Paul Dudley White published a seminal article in 1930 describing 11 patients who suffered from attacks of tachycardia associated with a sinus rhythm electrocardiographic (ECG) pattern of bundle branch block with a short PR interval. This was subsequently termed Wolff-Parkinson-White (WPW) syndrome, although earlier isolated case reports describing similar patients had been published.

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This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the Electrocardiogram (ECG) article more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.
In this article:
Diagnosis of Wolff-Parkinson-White Syndrome
MCQ exam: clinical scenario
MCQ exam: answer
MCQ exam: explanation

Diagnosis of Wolff-Parkinson-White Syndrome

The diagnosis of the WPW pattern, which usually requires only a surface ECG, is typically prompted by an incidental finding on an ECG obtained for another clinical indication. Identification of a short PR interval and a delta wave is usually adequate to confirm the diagnosis of the WPW pattern. In some rare circumstances, invasive electrophysiology testing can be helpful in confirming the diagnosis of an accessory pathway or detecting patients with short effective refractory periods (<250 milliseconds), for example in competitive athletes.

The diagnosis of WPW syndrome is typically made in a patient with a preexisting WPW pattern on an ECG who develops an arrhythmia that involves the accessory pathway, although some patients initially present with an arrhythmia and no known history of the WPW pattern.

MCQ exam: clinical scenario

In a patient with Wolff Parkinson White syndrome, the most characteristic finding on an ECG is:

a) ST segment elevation
b) Inversion of lead I
c) Q wave measuring 50% of QRS height
d) Delta waves
e) ST segment depression

MCQ questions & answers on medicalnotes.info

MCQ exam: answer

The correct answer is D.

MCQ explanation

This diagnosis should be suspected in persons with an arrhythmia and a very rapid ventricular heart rate, particularly when a delta wave can be identified and particularly in children or young adults presenting with a paroxysmal arrhythmia.

In WPW pre-excitation syndrome findings on the ECG include delta wave (initial slurring) of the QRS complex and short PR interval. The combination of PR interval <0.12 sec, a delta wave at the beginning of the QRS complex, and a rapid, regular tachyarrhythmia has been termed the Wolff-Parkinson-White (WPW) syndrome.

The PR interval is short because the descending electrical impulse bypasses the normal AV nodal conduction delay. The delta wave is produced by slow intramyocardial conduction that results when the impulse, instead of being delivered to the ventricular myocardium via the normal conduction system, is delivered directly into the ventricular myocardium via an abnormal or anomalous bundle. The QRS duration is prolonged because it begins too early.

See also the separate Q&A articles, Forms of Wolff-Parkinson-White Syndrome and Treatment Options for Wolff-Parkinson-White Syndrome.

UpToDate: Wolff-Parkinson-White syndrome: Anatomy, epidemiology, clinical manifestations, and diagnosis. Available online: https://www.uptodate.com/contents/wolff-parkinson-white-syndrome-anatomy-epidemiology-clinical-manifestations-and-diagnosis

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