An Athletic 37-Year-Old Woman With Suspicious Panic Attacks

Thomas J. Hemingway, MD


September 01, 2020

Preexcitation, or WPW syndrome, is an abnormality recognized on the surface ECG that represents an early activation of the ventricle outside the normal conduction pathway.[2] As normal atrial conduction occurs, an inherent delay is seen in the atrioventricular node prior to activation of the ventricles. With preexcitation, a communication or "accessory pathway" exists between the atria and ventricle that bypasses normal atrioventricular node conduction delay and activates some portion of the ventricle. The resultant beat is a fusion of early and normal ventricular activation.

The bundle of Kent, a communicating tract between the left atrial appendage and left ventricle, is a classic example of a preexcitation pathway. Localization of the various types of accessory pathways can often be achieved through the baseline ECG.[3] For example, in Figure 2, the delta wave is positive in V1 (moves toward V1) and negative in aVL (moves away from aVL), suggesting that this pathway is located in the left ventricle along the lateral wall.

Figure 2.

Atrioventricular accessory pathways are not the only mechanism of early ventricular activation. There are rare reports of atrio-Hisian (from atria to bundle of His) pathways, a condition known as Lown-Ganong-Levine (LGL) syndrome.[2] In LGL syndrome, the ECG demonstrates a short P-R interval (usually < 0.12 sec) without a delta wave and with a normal QRS complex.

Preexcitation is believed to have an estimated prevalence of 0.1%-0.3% in the general population. As in the original descriptions, preexcitation syndromes predispose patients (often otherwise young and healthy) to paroxysmal tachyarrhythmias, specifically atrioventricular reentrant tachycardias. Initially, these syndromes were thought to be benign until the recognition that atrial fibrillation in these patients can precipitate ventricular fibrillation.[4,5] Luckily, this patient presented prior to having such a lethal event.

As many as 80% of patients with WPW syndrome have reentrant tachycardia, 15%-30% have atrial fibrillation, and 5% have atrial flutter.[2] Ventricular fibrillation is estimated to occur in patients with recurrent tachycardia at about 0.1% of the time.


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