Prof. Mark O'Neill, Cardiologist and Professor of Electrophysiology

Prof. Mark O'Neill DPhil, FRCP, FHRS, MRCP, MB BCh BAO

Cardiologist and Professor of Electrophysiology

DPhil, FRCP, FHRS, MRCP, MB BCh BAO
Prof.Mark O'Neill,Cardiologist

Prof. O'Neill is a recommended Cardiologist and Professor of Electrophysiology

How do wearable devices like smart watches help heart rhythm experts?

How do wearable devices like smart watches help heart rhythm experts?

What is a heart palpitation and should I be worried?

What is a heart palpitation and should I be worried?

What is atrial fibrillation and is it dangerous?

What is atrial fibrillation and is it dangerous?

Prof. Mark O'Neill - Consulting

Prof. Mark O'Neill - Consulting

Areas of expertise

  • All arrhythmias
  • Atrial fibrillation
  • Catheter ablation
  • MRI
  • Clinical research

Recommendations for Prof. O'Neill

These recommendations are for information purposes only. Doctors providing recommendations do so in good faith and are not responsible for clinical outcomes.

Recommended by:

  • byDr Samina Showghi, GP

    Over the 10 years I have known and referred to Mark, he always provides the best care clinically, technically and psychologically to my patients and my family – there is no higher recognition possible. The ‘cardiac electrician’ not to be missed!

  • byDr Brian Clapp, Cardiologist

    Prof Mark O’Neill is a very knowledgeable specialist within his field of Electrophysiology. He always provides a valuable opinion for patients that I refer to him and, if required, has a high level of technical ability when undertaking procedures. I am confident in recommending him to my patients.

  • byDr James Harrison, Consultant Cardiologist

    Prof. Mark O'Neill is an outstanding clinician, who always provides an excellent opinion for patients with heart rhythm problems. He is an international expert in atrial fibrillation and I have no hesitation in recommending him to my patients.

  • byDr Matthew Wright, Cardiologist and Electrophysiologist

    Prof. Mark O'Neill really cares about individual patients and doing what's safe. He's technically excellent. If it was me, I'd have Prof. Mark O'Neill operate on me.

  • by Dr Sonja Meier, Pain Medicine Specialist

    He is exceptionally professional, compassionate and engaged. I would always recommend him to my friends and family!

  • byDr Samina Showghi, GP

    Over the 10 years I have known and referred to Mark, he always provides the best care clinically, technically and psychologically to my patients and my family – there is no higher recognition possible. The ‘cardiac electrician’ not to be missed!

  • byDr Brian Clapp, Cardiologist

    Prof Mark O’Neill is a very knowledgeable specialist within his field of Electrophysiology. He always provides a valuable opinion for patients that I refer to him and, if required, has a high level of technical ability when undertaking procedures. I am confident in recommending him to my patients.

  • byDr James Harrison, Consultant Cardiologist

    Prof. Mark O'Neill is an outstanding clinician, who always provides an excellent opinion for patients with heart rhythm problems. He is an international expert in atrial fibrillation and I have no hesitation in recommending him to my patients.

  • byDr Matthew Wright, Cardiologist and Electrophysiologist

    Prof. Mark O'Neill really cares about individual patients and doing what's safe. He's technically excellent. If it was me, I'd have Prof. Mark O'Neill operate on me.

  • by Dr Sonja Meier, Pain Medicine Specialist

    He is exceptionally professional, compassionate and engaged. I would always recommend him to my friends and family!

  • Address

    • The Heart Rhythm Clinic

      88 Harley Street, Marylebone, London, W1G 7HR

    • The Harley Street Clinic

      35 Weymouth Street, London, W1G 8BJ

    • The Harley Street Clinic Diagnostic Centre

      16 Devonshire St, Marylebone, London, W1G 7AF

  • Guy's Hospital (NHS)

    Great Maze Pond, London, Greater London, SE1 9RT

  • St Thomas' Hospital (NHS)

    Westminster Bridge Road, London, Greater London, SE1 7EH

  • About Prof. Mark O'Neill

    GMC number: 4636126

    Year qualified: 1998

    Place of primary qualification: University of Dublin

    Areas of expertise

    • All arrhythmias
    • Arrhythmias in adult congenital heart disease
    • Atrial fibrillation ablation
    • Cardiac electrophysiology
    • Atrial tachycardias
    • Bradycardia
    • Syncope
    • Heart rhythm disorders
    • Vasovagal syncope
    • Catheter ablation
    • Clinical research
    • MRI
    • Atrial septal defect
    • Patent foramen ovale
    • Palpitations
    • Radiofrequency catheter ablation
    • Supraventricular tachycardia
    • Ventricular tachycardia
    • Dizzy spells and blackouts
    • General cardiology
    • Wolff–Parkinson–White syndrome (WPW)

    Frequently asked questions

  • What are the common symptoms that your patients tend to present with?

    It's quite varied. If the patient has been appropriately referred, it is usually because of palpitations. That's the most common symptom among the patients that I would see.

    Patients may also be referred with dizzy spells, breathlessness, lightheadedness, or even loss of consciousness. Oftentimes, patients will have researched their symptoms online in advance and will have decided that they should visit a doctor. Ectopic beats are a common symptom for which patients self-refer.

    Sometimes a specific arrhythmia diagnosis has been made or suspected elsewhere and the patient has been referred for specialist arrhythmia-focused investigation and management. The most common confirmed diagnosis made elsewhere and for which I am referred patients is atrial fibrillation. Less common but very amenable to curative treatment is an ECG-confirmed diagnosis of either atrial flutter or supraventricular tachycardia.

    Some patients may have a family history of heart troubles and they just want to be checked out to make sure they don’t have the same problem.

  • What are the treatments that you're able to offer your patients?

    At The Heart Rhythm Clinic, we can investigate and treat every form of heart rhythm disorder. The treatments break down into two broad categories – those for bradycardia (excessively low heart rates) and tachycardia (excessively high heart rates). For bradycardia, the treatment may be implantation of a pacemaker; for tachycardia, the treatments options are broader and depend really very much on the diagnosis. This could vary from medication to catheter ablation to implantation of a defibrillator.

    The majority of our work is seeing patients who have symptoms, but who don’t necessarily need an intervention and distinguishing those from the patients who do need an intervention, or whose quality of life could be improved by considering one.

    The most common intervention by far that we perform is catheter ablation for atrial fibrillation which is not surprising as this is the most common heart rhythm disturbance!

  • What are your areas of sub-specialist interest?

    Our practice is built on a strong academic base. The consultant members of The Heart Rhythm Clinic are engaged in ongoing research into the conditions that we ultimately treat in patients, particularly atrial fibrillation. We have a very broad-reaching research portfolio to investigate mechanisms of atrial fibrillation, but also to identify the patients who would benefit most from intervention and hopefully to avoid invasive treatments in patients where the likelihood of arrhythmia cure is low.

    Atrial fibrillation is a blunt diagnosis, made on the basis of a single heart rhythm ECG recording but actually it represents a spectrum of electrical disorder of the heart. So, being able to tailor appropriately the investigation and management to the patient in front of us is very important. I would argue that this is something we do very well, helped in part by our extensive research work (over 250 peer-reviewed journal papers) specifically in the investigation and management of atrial fibrillation.

    We also have strong links with cardiac imaging, bioengineering, and computational modelling to support our research in atrial fibrillation. Although we are electrophysiologists, we have access to expertise in these complementary fields that permits us to offer something beyond standard electrophysiological practice. Whether that makes us better or not, I don’t know, but it certainly makes us evidence-based and unlikely to offer treatment on the basis of gut feeling or tradition!

    The investigation and treatment our patients receive are based on the most contemporary data in the field of arrhythmia medicine and where appropriate, our own published work.

  • Professional memberships

    Heart Rhythm Society
    European Heart Rhythm Association
    British Heart Rhythm Society
    General Medical Council
    Independent Doctors Federation grayscale

    Articles by Prof. Mark O'Neill

    Atrial Septal Defects and Patent Foramen Ovale

    Other specialists recommended by Prof. O'Neill