A 81-year-old woman is seen in the Emergency Department because of an episode of palpitation that lasted for over 2 hours, accompanied by dyspnea and weakness. Episodes of paroxysmal tachycardia had been occurring for over ten years, at first mild and responding to Valsalva maneuver, but recently more severe and prolonged, requiring treatment in the emergency department:

• Supraventricular tachycardia, 137/min
• AV Nodal Re-entrant Tachycardia (AVNRT)

Narrow QRS tachycardia, with P waves closely following the QRS. The P waves are negative (pseudo-S’) in II, III, aVF and V4-V6 and positive in aVR and aVL (the P wave axis is directed). The findings support the diagnosis of AVNRT.

Vagal stimulation maneuvers were carried out unsuccessfully. The arrhythmia subsided after IV injection of Adenosine. The patient became symptom-free:

• Sinus rhythm with 1st degree AV block
• Otherwise normal

Electrophysiology studies were carried out. Dual AV nodal physiology was demonstrated. Typical AVNRT was easily induced and reproduced the patient’s clinical tachycardia. The slow pathway was ablated and the arrhythmia could no longer be induced.

ECG 1

ECG 2