Case 14: Two Accessory Pathways Revealed by One Holter ECG

A 12-year-old girl with WPW syndrome and recurring palpitations was admitted for noninvasive and invasive testing of the accessory pathway. She was diagnosed with WPW syndrome 3 years before her presentation. She presented episodes of palpitations every 2 weeks, lasting between 5 min and 1 h. Vagal maneuvers could stop arrhythmia episodes. Upon admission, the patient’s blood pressure was 110/70 mmHg, heart rate was 80 beats per minute, and the ECG indicated a short PR interval of 80 ms and a delta wave, suggestive of ventricular preexcitation. An exercise test showed a maximum heart rate of 171/min with persistent preexcitation. Subsequently, a Holter ECG revealed a gradual disappearance of the preexcitation at a rate of 191/min. The abrupt disappearance of the delta wave is essential for evaluating the refractory period of the accessory pathway, which the Holter ECG was unable to detect in this case. The refractory period of the accessory pathway was evaluated invasively by an electrophysiological study due to the limitations of noninvasive testing (Figs. 20.1, 20.2, 20.3, 20.4, 20.5, 20.6, 20.7, 20.8, 20.9, 20.10, 20.11, 20.12, 20.13, 20.14, 20.15, 20.16, 20.17, 20.18, 20.19, 20.20, 20.21, 20.22, and 20.23).