1 Oxford Heart Centre, Oxford University Hospitals NHS Foundation Trust, Oxford, UK.
2 Department of cardiology, Taunton and Somerset NHS Foundation Trust, Musgrove Park, Taunton, UK.
3 Department of cardiology, Guy's and St Thomas' Hospitals NHS Foundation Trust, London, UK.
4 Department of oral and maxillofacial medicine, surgery & pathology, University of Sheffield School of Clinical Dentistry, Sheffield, UK m.thornhill@sheffield.ac.uk.