Cerebrovascular accident and acute coronary syndrome and perioperative outcomes (CAPO) study protocol: a 10-year database linkage between Hospital Episode Statistics Admitted Patient Care, Myocardial Infarction National Audit Project and Office for National Statistics registries for time-dependent risk analysis of perioperative outcomes in English NHS hospitals

Introduction: An increasing number of people who have a history of acute coronary syndrome or cerebrovascular accident (termed cardiovascular events) are being considered for surgery. Up-to-date evidence of the impact of these prior events is needed to inform person-centred decision making. While perioperative risk for major adverse cardiac events immediately after a cardiovascular event is known to be elevated, the duration of time after the event for which the perioperative risk is increased is not clear.

Methods and analysis: This is an individual patient-level database linkage study of all patients in England with at least one operation between 2007 and 2017 in the Hospital Episode Statistics Admitted Patient Care database. Data will be linked to mortality data from the Office for National Statistics up to 2018, for 30-day, 90-day and 1-year mortality and to the Myocardial Ischaemia National Audit Project, a UK registry of acute coronary syndromes. The primary outcome will be the association between time from cardiovascular event to index surgery and 30-day all-cause mortality. Additional associations we will report are all unplanned readmissions, prolonged length of stay, 30-day hospital free survival and incidence of new cardiovascular events within one postoperative year. Important subgroups will be surgery specific (invasiveness, urgency and subspecialty), type of acute coronary syndrome (ST or non-ST elevation myocardial infarction) and type of cerebrovascular accident (ischaemic or haemorrhagic stroke).

Ethics and dissemination: Ethical approval for this observational study has been obtained from East Midlands-Nottingham 1 Research Ethics Committee; REC reference: 18/EM0403. The results of the study will be made available through peer-reviewed publications and via the Health Services Research Centre of the Royal College of Anaesthetists, London.