4th May 2025

A 32-year-old female presents with light-headedness and palpitations.

A 32-year-old female presents with light-headedness and palpitations. She notes in the past she has had similar episodes lasting 10-15 mins and each time they have spontaneously resolved on its own. Clinical examination shows a blood pressure of 120/95 mmHg and a heart rate of 175bpm. The ECG shows an irregularly irregular rhythm with no P waves and a QRS of 135ms.

A trial of adenosine is given. Shortly after this, the patient loses consciousness, and her monitor shows a broad-based tachycardia before going into cardiac arrest.

What is the likely underlying diagnosis?

Select the SINGLE most appropriate option from the list below. Select ONE option only.