6.41

Minnesota Code 6-4-1: WPW pattern — short PR, delta wave, risks of tachycardia and atrial fibrillation, and ablation.

Code 6.41 — Minnesota Code 6-4-1: Wolff–Parkinson–White (WPW) pattern. Besides the normal AV node, the heart has an extra electrical connection between the atria and the ventricles: an accessory pathway. Part of the ventricle is activated early ("pre-excitation"). The ECG shows a short PR interval (< 120 ms), a slurred initial upstroke of the QRS called the delta wave, and a wide QRS. When the pattern is accompanied by episodes of tachycardia, it is called WPW syndrome.

Minnesota Code 6Pre-excitationAccessory pathway

PR interval< 120 ms

Delta waveslurred QRS onset

QRSwidened, often ≥ 120 ms

Prevalenceabout 1–3 per 1000

Figure 1. Left: normal conduction. Right: WPW pattern — short PR, slurred delta wave at the start of the QRS and a widened QRS with secondary ST-T changes.

Why it matters

The accessory pathway can form an electrical circuit with the AV node and cause atrioventricular re-entrant tachycardia, a sudden, regular, fast heartbeat. A less common but dangerous situation is atrial fibrillation in WPW. If the pathway conducts quickly, impulses can reach the ventricles very rapidly, and this can degenerate into ventricular fibrillation. The risk of sudden cardiac death is low but real, which is why the pattern needs specialist assessment, even in people without symptoms.

Medicines

In atrial fibrillation with pre-excitation, drugs that block the AV node (adenosine, verapamil, diltiazem, digoxin, and intravenous amiodarone) can be dangerous, because they may increase conduction over the accessory pathway. Always tell medical staff that you have WPW.

Diagnosis and treatment

Assessment of risk may include exercise testing, Holter monitoring and an electrophysiological study. Catheter ablation of the accessory pathway cures the condition in most patients and is the treatment of choice in symptomatic WPW. It is also considered in asymptomatic people whose pathway has high-risk properties.

Seek emergency care

if you have WPW and develop a very fast or irregular heartbeat, dizziness, fainting, chest pain or breathlessness.

References

Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia. Circulation. 2016;133(14):e506–e574. doi:10.1161/CIR.0000000000000311
Surawicz B, Childers R, Deal BJ, Gettes LS. AHA/ACCF/HRS recommendations for the standardization and interpretation of the electrocardiogram: part III: intraventricular conduction disturbances. Circulation. 2009;119(10):e235–e240. doi:10.1161/CIRCULATIONAHA.108.191095
Prineas RJ, Crow RS, Zhang ZM. The Minnesota Code Manual of Electrocardiographic Findings. 2nd ed. London: Springer; 2010. doi:10.1007/978-1-84882-778-3

This article is for general information and does not replace a consultation with a doctor. ECG findings must be interpreted by a physician together with symptoms and other tests.

Published on 14 May 2019