Dr Iain Sim

Chest pain | breathlessness |  palpitations| fainting (syncope) | coronary artery disease and heart failure — with a specialist focus on arrhythmia and cardiac devices. 

Dr Iain Sim is a Consultant Cardiologist and Electrophysiologist at Frimley Health. He specialises in the diagnosis and treatment of heart rhythm disorders (arrhythmias) and practices across Frimley Park and Wexham Park Hospitals.

He manages a full range of cardiac conditions including chest pain, breathlessness, palpitations, fainting (syncope), coronary artery disease and heart failure — with a specialist focus on arrhythmia and cardiac devices. 

His clinical expertise spans catheter ablation for atrial fibrillation (including pulsed field ablation), atrial flutter, supraventricular tachycardia (SVT), ectopic beats and ventricular tachycardia, alongside complex cardiac device implantation including pacemakers, defibrillators (ICDs) and conduction system pacing. His further interests include inherited cardiac conditions and in identifying and protecting patients at risk of dangerous heart rhythms.

Qualifications & training

MBBS, St George’s, University of London · Member of the Royal College of Physicians (MRCP(UK)) · PhD, King’s College London · CCT in Cardiology, with specialist accreditation in cardiac electrophysiology and devices · 

Dr Sim held senior registrar posts at leading UK centres including the Royal Brompton and Harefield Hospitals, King’s College Hospital and the Royal Sussex County Hospital , where he developed his expertise in cardiac electrophysiology.

Research & academic interest

Dr Sim completed his PhD within the cardiac electrophysiology and imaging group at King’s College London, under Professor Mark O’Neill. His work focused on the mechanisms that drive atrial fibrillation and ventricular arrhythmias, and on using advanced imaging to guide treatment. His published research includes MRI-guided electrophysiology and ablation, patient-specific computational modelling to predict ablation outcomes in persistent atrial fibrillation, the characterisation of atrial fibrosis and atrial cardiomyopathy, and tools for analysing electroanatomic mapping data. His work has appeared in journals including Circulation: Arrhythmia and Electrophysiology, Europace and the Journal of Cardiovascular Electrophysiology.

This research background informs his everyday practice: a detailed, evidence-based approach to diagnosing the cause of a patient’s symptoms and tailoring treatment to the individual. Known for his patient-centred approach, Dr Sim combines clinical excellence with clear communication to ensure patients feel informed, reassured, and supported throughout their care.