Mark O'Neill


26 years of experience
26 years of experience



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Professor O’Neill is a Consultant Cardiologist and Professor of Cardiac Electrophysiology, who sees private patients at The Cardiac Clinic at London Bridge Hospital. He completed a DPhil in Cardiac Physiology at the University of Oxford as a Rhodes Scholar in 1995 before graduating with first-class honors from University College Dublin in 1998. He completed his subspecialty training in interventional cardiac electrophysiology at St Mary’s Hospital and in the internationally renowned arrhythmia centre in Bordeaux.

He became a Reader in 2011 and was appointed a Professor in 2013. Since then, he has led the arrhythmia service, the regional training program, and the cardiac electrophysiology divisional research program. He was awarded a National Bronze Clinical Excellence award in 2016 and 2021 in recognition of the quality and breadth of both his clinical and academic work.

In his current role, Professor O’Neill treats patients with all manner of palpitations, including those caused by simple and complex heart rhythm conditions such as supraventricular tachycardia, atrial fibrillation, atrial flutter/tachycardia, arrhythmias associated with adult congenital heart disease and ventricular tachycardia. Where appropriate, he performs interventional electrophysiology procedures to manage these conditions. He spends time helping his patients to understand fully their symptoms and works with them to develop tailored treatment plans to suit their needs and concerns.

Outside of his clinical work, Professor O’Neill is an international opinion leader in cardiac electrophysiology. He is actively involved in research and has published widely in peer-reviewed journals. His research addresses the mechanisms of atrial fibrillation and the use of imaging and computational modeling techniques to improve clinical outcomes of AF ablation. He lectures regularly both in the UK and overseas on the management of atrial arrhythmias.

Diseases, Medical Tests and Treatments

  • Catheter ablation
  • AF ablation
  • Pulmonary vein isolation
  • Electrophysiology Study
  • DC Cardioversion
  • Implantable Loop Recorder
  • Ambulatory heart rhythm monitoring (1-14 days)
  • Atrial fibrillation
  • Atrial tachycardia
  • Atrial flutter
  • Arrhythmia in adult congenital heart disease
  • Supraventricular Tachycardia
  • Ventricular Tachycardia



All procedures

  • ECG (Electrocardiogram)
  • CT Coronary Angiogram
  • ECG Holter Monitor
  • Echocardiogram
  • Calcium Coronary Score
  • Cardioversion
  • Stress Echocardiogram
  • 24 Hour Blood Pressure Monitor
  • Cardiac MRI
  • Health Assessments
  • Heart & Lung Health Assessments
  • Heart Scan
  • Transoesophageal Echocardiogram
  • Video Consultation

All conditions

  • Atrial Fibrillation
  • Arrhythmia (Irregular Heartbeat)
  • Palpitations
  • Breathlessness
  • Atrial Flutter
  • Tachycardia
  • Adult Congenital Heart Disease
  • Bradycardia
  • Chest Pain
  • Dizziness
  • Fainting
  • Heart Attack
  • Loss of Consciousness (Syncope)
  • Supraventricular Tachycardia (SVT)
  • Ventricular Fibrillation


French, English



Registered with

General Medical Council: 4636126


St Olaf House 27 Tooley Street, London, SE1 2PR

  • Wednesday:
    2:00 PM - 7:00 PM

Consultation Fees

New appointment: £300

Follow-up appointment: £160


Overall Rating

Overall rating

Overall experience

5 / 5

Personal care received

4.96 / 5

Explanation of care provided

4.96 / 5



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