Wolff-Parkinson-White syndrome (WPW) is a syndrome of pre-excitation of ventricles of the heart due to an accessory pathway known as the bundle of Kent. This accessory pathway is an abnormal electrical communication from the atria to the ventricles, in addition to the AV node. 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.
WPW syndrome is commonly diagnosed on the basis of the surface ECG in an asymptomatic individual. In this case it is manifested as a delta wave, which is a slurred upstroke in the QRS complex that is associated with a short PR interval. The short PR interval and slurring of the QRS complex is actually the impulse making it through to the ventricles prematurely (across the accessory pathway) without the usual delay experienced in the AV node.
When an individual is in normal sinus rhythm, the ECG characteristics of WPW syndrome are a short PR interval, widened QRS complex (greater than 120 ms in length) with slurred upstroke of the QRS complex, and secondary repolarization changes reflected in ST segment-T wave changes.
If the patient experiences episodes of atrial fibrillation, the ECG will show a rapid polymorphic wide-complex tachycardia (without torsades de pointes). This combination of atrial fibrillation and WPW is considered dangerous, and most antiarrhythmic drugs are contraindicated.
下圖是：WPW + PSVT 的樣子
急診同仁不能不知道的 WPW syndrome！
重點：如果WPW+Af，不要誤判為Torsades de pointes，也不能給 A-V nodal blocking agents〔如 Adenosine, Isoptin, Digoxin...〕