Background
With 40 per cent of elective surgery occurring in patients aged 65 years and over, and frailty significantly prevalent amongst this cohort, cardiac complications will affect hundreds of thousands of older Australians undergoing surgery annually. Myocardial injury after noncardiac surgery (MINS) and postoperative myocardial infarction (MI) are common, and associated with substantial mortality risk. Unfortunately, almost 90 per cent of MINS is clinically silent, and therefore cannot be diagnosed without systematic troponin testing. International society guidelines currently recommend postoperative troponin surveillance in high-risk patients. However, a pressing knowledge gap is how preoperative assessment can accurately identify such individuals at high risk of MINS and MI, who will benefit from postoperative troponin screening.
Aims
To examine how the combination of functional capacity (measured by the Duke Activity Status Index) and frailty predicts postoperative cardiac complications in older patients undergoing intermediate-to-major surgery. This will form the basis of a larger study, which will develop a risk model to identify individuals at elevated risk of cardiac complications, who will benefit from postoperative cardiac surveillance.
Significance of Outcomes
Identifying individuals at increased risk of postoperative cardiac complications will enable initiation of appropriate postoperative monitoring and open potential avenues for secondary prevention therapy (such as aspirin, cholesterol agents and risk factor modification). With increasing numbers of elderly individuals undergoing surgery in Australia over the next two decades, accurate stratification of high-risk patients is crucial in preventing thousands of cardiovascular complications annually.
Objectives
1. Determine the incidence of MINS and postoperative MI in a high-risk cohort of patients in a Victorian metropolitan hospital;
2. Investigate how the Duke Activity Status Index (DASI) score, when combined with a Frailty Index (FI), is associated with MINS and postoperative MI;
3. Examine postoperative outcomes amongst individuals with MINS or postoperative MI, who undergo troponin surveillance with early cardiology consultation and
4. Conduct a cost analysis to evaluate the cost of troponin screening and early cardiology intervention vs the cost of missing diagnoses of MINS or postoperative MI.
Methods
Single-centre, prospective cohort study, in adults aged 65 years and over, undergoing elective, intermediate-to-major surgery at the Royal Melbourne Hospital, with a planned postoperative stay of at least one night. Patients presenting to preadmission clinic will be eligible for participation. The planned sample size is 300 patients. Preoperative data will include the DASI score, FI and other co-morbidities. Three postoperative troponin levels will be obtained, with an electrocardiogram (ECG) at each troponin measurement. The primary outcome is a composite of in-hospital MINS and MI and 30-day MI. Secondary outcomes are days alive at home at 30 days and 1-year myocardial infarction, coronary revascularisation and mortality. Patients recruited to this study will undergo normal hospital processes, with postoperative care at the discretion of the attending clinicians according to institutional protocols.
Likely benefits of research project
MINS and postoperative MI have been established as postoperative complications of prognostic importance. Emerging data suggests secondary prevention measures instituted in patients diagnosed with MINS can potentially reduce cardiovascular complications. Therefore, with increasing numbers of elderly patients undergoing elective surgery in Australia each year, accurate identification of MINS will represent a major step in potentially preventing thousands of postoperative cardiovascular complications and deaths. The findings from this study will help inform future interventional secondary prevention research. There is hence major potential impact on elderly surgical patient health outcomes and quality of life, with reduced economic burden of longer-term myocardial events.
Dr Earlene Silvapulle, Staff Specialist Anaesthetist, Department of Anaesthesia & Pain Management, Royal Melbourne Hospital, Parkville, Victoria. Research Fellow & PhD candidate, Department of Critical Care, University of Melbourne, Parkville, Victoria.
The project was awarded A$89,241 (including scholarship) funding through the ANZCA research grants program for 2024.