Wolff Parkinson White (WPW) syndrome
See brief interpretation of 12 lead EKG above
– a delta wave is seen, most clearly in the precordial leads (note that it may be negative)
– PQ interval ≤ 120 ms
– QRS complex ≥ 120 ms
Wolff Parkinson White (WPW) syndrome is characterized by an accessory conduction pathway between the atria and the ventricles.
The accessory pathway causes pre-excitation of the ventricles leading to the characteristic delta wave on the EKG seen as a slurred, early upstroke of the QRS complex. Also, because of the delta wave, the PQ interval is shortened (≤ 120 ms) and the QRS complex is prolonged (≥ 120 ms). Finally secondary ST segment and T wave changes may be seen.
The location of the accessory bundle varies. It may be situated near the septum or in the left or right myocardial walls. Complex algorithms exist to define the anatomic location of the accessory bundle from a 12 lead EKG.
The accessory bundle may be concealed in which it is only capable of conducting from the ventricles to the atria (retrograde conduction). In this case no pre-excitation occurs and the EKG will be normal during sinus rhythm.
Concealed or not – the accessory bundle may result in the formation of a supraventricular tachycardia (atrioventricular re-entrant tachycardia, AVRT). In this case the EKG presents with high ventricular rate (140-250 beats/min). The delta wave is not visible during tachycardia and the QRS complexes may be narrow or wide.
However, when Wolff Parkinson White syndrome is seen with atrial fibrillation delta waves are present (the mechanism in which the tachycardia arise is different).
Wolff Parkinson White syndrome may cause paroxysmal palpitations, dyspnoea and syncope due to episodes of tachycardia. Also sudden cardiac death occurs. The definitive treatment of Wolff Parkinson White syndrome is a radio frequency catheter ablation in which the accessory bundle is destroyed.