5th May 2025

Miss Smith is a 19-year-old university student who is referred by her GP to the general cardiology clinic.

Miss Smith is a 19-year-old university student who is referred by her GP to the general cardiology clinic. She reports periods of ‘total blackout’ with loss of consciousness. She first noticed her symptoms when she was playing a football match and suddenly passed out on the pitch. She states she was brought to the emergency department as her heart rate was very low but was discharged as she felt very well in herself soon afterwards. She noticed recurrence of these symptoms when she was running on a treadmill in the gym, but did not present to the emergency department at the time. She has no past medical history of note but states her father also had similar symptoms and has a pacemaker. She is a lifelong non-smoker and has a normal BMI. Clinical examination is unremarkable and she looks euvolaemic. A 12-lead ECG shows a PR interval of 210ms. A transthoracic echocardiogram is unremarkable. What is the next most appropriate investigation?

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