Professor Mark O'Neill

Professor Mark O'Neill

The Cardiac Clinic

Cardiology 04636126


  • Bupa Platinum consultant
  • Fee assured
  • Open Referral network
Bupa Platinum consultant
Fee assured
Open Referral network

Specialises in

  • Electrophysiology
  • General cardiology


  • Face-to-face consultations
  • Video and telephone consultations

About us

Professor Mark O’Neill 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.

In October 2009, he joined St Thomas’ Hospital and King’s College London in the Department of Cardiology and School of Biomedical Engineering and Imaging Sciences. He was promoted to Reader in 2011 and Professor in 2014. He is the Departmental Lead for Arrhythmias in Adult Congenital Heart Disease, the Divisional research lead for electrophysiology and the Service lead for Cardiac Electrophysiology and Devices. He currently supervises five PhD students and has published over 250 peer-reviewed papers, books and proceedings in the field of arrhythmia medicine.

He is an internationally recognized expert in catheter ablation of atrial fibrillation and tachycardia. He founded the London Deanery Subspecialty Electrophysiology Training Programme in 2008 and is the South London Training Programme Director for Electrophysiology. He is an editorial board member of three specialist electrophysiology journals and has served as a scientific programme committee member of the Heart Rhythm Society and currently European Heart Rhythm Society, the largest professional associations in the field of arrhythmia medicine.

He sees patients privately at 88 Harley St and the Harley St. Clinic. He performs electrophysiological interventions for simple and complex arrhythmias using the very latest techniques and technologies at both the Harley St Clinic and St. Thomas’ Hospital, London where he is the Director of the Translational XMRI Cardiac intervention Research Facility.

Areas of interest

Palpitations; Atrial fibrillation ablation; Cardiac electrophysiology; Radiofrequency catheter ablation; Arrhythmias; Ablation; Arrhythmias in adult congenital heart disease; magnetic resonance imaging; Supraventricular tachycardia; Ventricular tachycardia;

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Anaesthetists worked with

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Information for healthcare professionals

Information for healthcare professionals (Bupa patients only, last 12 months)

Procedures completed

  • 20365

    Follow-up out-patient consultation - remote - (5-50)

  • K5760

    Ablation of atrial fibrillation by isolation of the pulmonary veins (RFA/CRYO/laser) (including mapping) - (5-50)

    London Bridge Hospital (1-5)

  • 64302

    Transoesophageal echocardiography (including reporting) (as sole procedure) - (5-50)

    London Bridge Hospital (1-5)

  • K5780

    Ablation of accessory pathway or selected modification of AV node (including mapping) - (1-5)

    London Bridge Hospital (1-5)

  • K5730

    Ablation of atrial arrhythmia (including mapping) - (1-5)

  • X5020

    External cardioversion - (1-5)

    London Bridge Hospital (1-5)

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