How should an ECG be reported when it shows a Wolff-Parkinson-White (WPW) pre-excitation pattern?

How to Report an ECG with WPW Pattern

An ECG should be reported as showing "ventricular pre-excitation pattern" or "Wolff-Parkinson-White (WPW) pattern" when it demonstrates the classic triad: PR interval <0.12 seconds, delta wave (slurred initial QRS upstroke), and QRS duration >0.12 seconds with discordant ST-T wave changes. 1

Essential Diagnostic Criteria

The formal ECG report must document these four specific features 1, 2:

1. PR interval <120 milliseconds (shortened due to accessory pathway bypassing the AV node)
2. Delta wave - the characteristic slurring of the initial QRS upstroke representing early ventricular activation
3. QRS duration >120 milliseconds (widened from fusion of pre-excited and normal ventricular activation)
4. Secondary repolarization changes - ST segment and T wave abnormalities directed opposite (discordant) to the major delta wave and QRS vector

Critical Reporting Distinctions

Distinguish between "WPW pattern" versus "WPW syndrome" in your report. 1

• WPW Pattern (Asymptomatic Pre-excitation): Report as "ventricular pre-excitation pattern consistent with accessory pathway" when the ECG shows the above features but the patient has no documented arrhythmias or symptoms
• WPW Syndrome: Only use this term when pre-excitation is accompanied by documented supraventricular tachycardia or symptoms consistent with SVT 1

This distinction has major clinical implications - the pattern alone doesn't warrant the "syndrome" diagnosis.

Important Reporting Caveats

Pre-excitation can be intermittent or subtle - if delta waves are not clearly visible on the current ECG but clinical suspicion exists, report "consider serial ECGs to evaluate for intermittent pre-excitation" 1, 3. The degree of pre-excitation varies based on:

• Accessory pathway location and conduction properties
• Relative contribution of AV nodal versus accessory pathway conduction
• Autonomic tone

When reporting wide-complex tachycardia in a patient with known WPW, specify the suspected mechanism 3, 4:

• Pre-excited atrial fibrillation (irregular, wide, variable QRS morphology)
• Antidromic AVRT (regular, maximally pre-excited wide QRS)
• Note that ventricular tachycardia cannot be reliably excluded by ECG alone

Structured Reporting Template

Your ECG report should include:

Rhythm: Sinus rhythm with ventricular pre-excitation pattern (WPW pattern)

Intervals:

• PR interval: [specific measurement] ms (shortened, <120 ms)
• QRS duration: [specific measurement] ms (prolonged, >120 ms)

Morphology: Delta wave present in leads [specify leads], consistent with [location if determinable - e.g., left lateral, posteroseptal] accessory pathway

Repolarization: Secondary ST-T wave changes, discordant to QRS vector

Clinical Correlation: Recommend clinical correlation for symptoms of supraventricular tachycardia. If asymptomatic, consider cardiology referral for risk stratification.

Common Pitfalls to Avoid

• Don't report as "bundle branch block" - the wide QRS is from pre-excitation, not conduction system disease
• Don't miss intermittent pre-excitation - compare with prior ECGs if available 3
• Don't use "WPW syndrome" for asymptomatic patients - this requires documented arrhythmias 1
• In atrial fibrillation with pre-excitation, explicitly state "pre-excited atrial fibrillation" as this is a medical emergency requiring different management than typical AF 5, 4