A 35 year old lady presents following an episode of rapid, regular palpitations felt as a "rapid pounding sensation in her neck", which was abrupt in onset, lasted for around 20 minutes and terminated suddenly, without treatment. She is also polyuric. The paramedics obtained an ECG during the episode. She has experienced a few shorter but similar episodes during the last 2 to 3 months. She is otherwise healthy and is not on any drugs.
The ECG obtained en-route shows a narrow complex tachycardia with a rate of 200 bpm and a regular rhythm.
The resting ECG is significant for delta waves and a short PR interval.
The echocardiogram appears normal, with an ejection fraction of 65%. No structural or valvular cardiac defects or regional wall motion abnormalities are noted.
Electrophysiological studies show a single, left posteroseptal accessory pathway. Ventricular tachycardia induction studies are negative.