1. aDepartment of Anesthetics and Critical Care, Harefield Hospital, Royal Brompton and Harefield Hospitals, Guy’s and St Thomas NHS Foundation Trust
2. dSchool of Cardiovascular Sciences and Medicine, King’s College London
3. bDepartment of Medical Biotechnologies, Division of Cardiology, University of Siena, Siena, Italy
4. cInstitute of Clinical Physiology, National Research Council, Pisa, Italy