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Mark O'Neill





English, French

NHS Base

Guy's and St Thomas' Hospital

Clinics at


020 7636 6363


Professor Mark O'Neill is a Consultant Cardiologist and Professor of Cardiac Electrophysiology.  He completed his undergraduate medical and postgraduate scientific training at University College Dublin and the University of Oxford before embarking on specialist medical and cardiology training in London. 

In 2005, he undertook a specialist training fellowship in cardiac electrophysiology in Bordeaux with Professors Michel Haissaguerre and Pier Jais, specifically to develop expertise in catheter ablation of atrial fibrillation before being appointed Senior Lecturer and Consultant Cardiologist at Imperial College and St. Mary’s Hospital, London. 

In 2009, Professor O'Neill joined Guy's and St Thomas' where he is a Professor in Cardiac Electrophysiology and acts as the Electrophysiology lead for the Cardiovascular Clinical Academic Group at King’s Health Partners.

He is a council member of Heart Rhythm UK, the training lead for EP in the London Deanery and directly supervises students towards the PhD degree at Kings College London, in addition to maintaining a full clinical workload as an NHS consultant cardiologist. He is a regularly invited faculty member for major international arrhythmia meetings and is widely published in the subspecialty of arrhythmia medicine.

His specialist interest is in the management of patients with complex heart rhythm disturbances of atrial and ventricular origin, in particular atrial fibrillation and tachycardia in the context of inherited and acquired structural heart disease.

Special Interests

All arrhythmias, atrial fibrillation, catheter ablation, MRI, clinical research.

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