Mark O'Neill


Consultant cardiologist and professor of cardiac electrophysiology


Mark O'Neill has been a consultant cardiologist at Guy's and St Thomas' NHS Foundation Trust since 2009. He leads the clinical research group in cardiac electrophysiology.

Before this he was a senior Lecturer and honorary consultant cardiologist at Imperial College Healthcare NHS Trust.

He is a council member of Heart Rhythm UK.

He is a training lead in the London Deanery and supervises PhD students at King's College London.

He is regularly invited to major international arrhythmia meetings and is widely published.

Education and training

  • Fellowship of the Royal College of Physicians, 2012
  • Fellowship of the Heart Rhythm Society, 2011
  • Certificate of completion of specialist training in cardiology, 2007
  • Membership of Royal College of Physicians, 2001
  • Medicine and surgery (MB BCh), First-Class Honours, University College Dublin, 1998
  • DPhil in physiological sciences, Rhodes Scholar, University of Oxford, 1995

Specialist Registrar

  • Academic Clinical Lecturer in Cardiology, Imperial College Healthcare NHS Trust, 2007 to 2008
  • British Heart Foundation International Fellowship, Hôpital Cardiologique du Haut Lévêque, Bordeaux, 2005 to 2007
  • Specialist registrar in cardiology, Imperial College Healthcare NHS Trust, 2003 to 2005
  • Specialist registrar in cardiology, Central Middlesex Hospital, 2002 to 2003
  • Specialist registrar in cardiology, Hillingdon Hospital, London, 2001 to 2002

Senior House Officer

  • Whittington Hospital, 2000 to 200
  • Royal Brompton Hospital and Hammersmith Hospital, 1999 to 2000

House Officer

  • Intern to the Medical and Surgical Professorial Units, Mater Hospital, Dublin, 1998 to 1999

Research interests

  • Comparison of fibrosis determined by MRI and electrical conduction properties
  • Evaluation and study of ablation lesions using MRI
  • Use of new catheter technologies for ablation


  • Ruben Harvey prize for highest aggregate mark in medicine, surgery and obstetrics in Dublin Medical Schools, Royal College of Physicians of Ireland, 1998
  • Mater Hospital gold medal in medicine, 1998
  • Surgeon Hugh Kennedy Boyle bequest for best performance in surgical finals, 1998
  • Rhodes Scholarship, University of Oxford
  • Colman Saunders medal in paediatrics
  • Kirwan medal and prize
  • Dwyer Joyce Prize in ophthalmology
  • Dr Henry Hutchinson Stewart prize in physiology 1992
  • Dr Henry Hutchinson Stewart prize in pharmacology, 1992
  • Dillon memorial prize in pharmacology, 1992
  • Research scholarship, Health Research Board 1992
  • Dr Henry Hutchinson Stewart prize in biochemistry, 1991 
  • Ambrose Birmingham medal in anatomy, 1991 

Last updated: January 2023

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