Patients in this study were drawn from the Second Medical Center, Chinese PLA General Hospital. We included consecutive patients undergoing non-cardiac surgery who were at least 80 years of age and had a troponin measurement within the first 24 h and 3 days after surgery between January 1, 2011, and January 1, 2021.

Data were collected from electronic health records (EHR) from our hospital. The variables collected included demographics, laboratory measurements, troponin I concentrations, disease diagnosis, comorbidities, procedures, and outcomes. Comorbidities were extracted using International Classification of Disease-Revision 9/10 billing codes for atrial fibrillation (AF), asthma, coronary artery disease (CAD), cancer, chronic kidney disease (CKD), chronic obstructive pulmonary, diabetes (DM), heart failure (HF), and hypertension (HTN). Troponin T concentrations were assessed and the reference level for normal is <0.03 ng/ml. The clinical follow-up data were obtained using direct contact with the patients, their referring physicians, and family physicians.

The PMI was defined as a peak plasma troponin T concentration of 0.03 ng/ml or greater than resulted from myocardial ischemia within 3 days after surgery. The pre-operative assessment was carried out by physicians.

Trained research personnel reviewed the charts to obtain information on potential preoperative predictors of major perioperative complications by using standardized definitions. The Revised Cardiac Risk Index (RCRI) was calculated in all patients to estimate cardiovascular risk. The RCRI has six predictors of risk as to the following: creatinine ≥2 mg/dl, heart failure, insulin-dependent diabetes mellitus, intrathoracic, intra-abdominal, or suprainguinal vascular surgery, history of cerebrovascular accident or Transient Ischaemic Attack (TIA), and ischemic heart disease. Each predictor is worth 1 point. Patients with more predictors of risk would have a higher risk.

Postoperative pulmonary complications were evaluated by using a seven-variable risk assessment tool Assess Respiratory Risk in Surgical Patients in Catalonia (ARISCAT). The ARISCAT score included seven independent risk factors: low preoperative arterial oxygen saturation, acute respiratory infection during the previous month, age, preoperative anemia, upper abdominal or intrathoracic surgery, surgical duration of at least 2 h, and emergency surgery (8).

Hypotension was defined as a mean arterial pressure (MAP) below 65 mm Hg for at least 1 min (9).

Major bleeding was defined using modified International Society on Thrombosis and Haemostasis (ISTH) criteria to include any one of the following: (1) fatal bleeding, (2) bleeding into a critical area or organ, (3) fall in hemoglobin of ≥ 2 g/dl over 24 hours, (4) transfusion of two or more units of whole blood or packed red blood cells over 24 h, and in surgical patients, and (5) surgical site bleeding that required a second intervention (10).

We excluded patients who were incorrectly screened (<80 years, <24-h hospital stays), had their surgery canceled, had cardiac surgery or MI within 14 days before surgery. For the analysis addressing 30-day and 1-year mortality, we only included every patient once at first enrollment.

Descriptive analyses were performed by troponin T levels stratified into normal and elevated groups (more than the upper limit of normal, >0.03 ng/ml). We used troponin measurements within 3 days after the operation. If multiple troponin measurements were available within 24 h, the patient's highest measurement was used. Categorical variables were reported as total count and percentage of patients. Continuous no troponin laboratory values were reported as median and interquartile range. The characteristics of patients who did and did not develop PMI were compared using the Chi-square test for categorical variables and the Student's t-test for continuous variables. Multivariable logistic regression analysis was used to estimate the independent predictors of myocardial injury after non-cardiac surgery. We report the 30-day mortality and other important 30-day outcomes (non-fatal cardiac arrest, congestive heart failure, stroke, and composite of major events) for patients with and without PMI. To assess the effects of PMI on outcomes, we conducted a survival analysis with the dependent variable of time to mortality, setting the time of days after the operation.

A total of 2,984 surgeries met our inclusion criteria. The baseline characteristics of the surgical patients who did and did not develop PMI are reported in Table 1. All the patients underwent troponin measurement every day within 3 days after the operation. Approximately 50% of PMI occurs on the day of surgery, and 18% on the second postoperative day. The mean [±standard deviation (SD)] age of the patients was 83.7 ± 8.25 years. The majority of participants were classified as either ASA class 2 (70.38%) or ASA class 3 (23.39%) before surgery. More often, patients with PMI had coronary artery disease, atrial fibrillation, peripheral artery disease, prior stroke, diabetes mellitus, chronic obstructive pulmonary disease (COPD), active tumor disease, and had a higher ARISCAT score than patients who did not develop PMI.

The overall incidence of PMI was 418/2,984 (14%). In clinical presentation, the ECG changes within 7 days in patients experiencing a PMI were shown in Table 2. Among the surgical patients who suffered PMI, 156 (37.32%) patients had palpitations and forty (9.57%) patients had clinical ischemic symptoms. The most common ischemic ECG findings were T wave inversion (32.54%) and ST-segment depression (24.4%). Twenty patients were with ECG findings of LBBB and the mortality at 30 days was as high as 10%. In multivariable analyses, coronary artery disease [adjusted OR (aOR) 1.92 95% CI (1.43–2.69)], chronic heart failure [aOR 2.16 95% CI (1.48–4.15), and hypotension [aOR 2.79 95% CI (1.88–4.20) were independently associated with the development of PMI (Table 3).

Patients who suffered from PMI were at higher risk of death (OR, 2.69; 95% CI, 1.78–3.65; P < 0.001), non-fatal cardiac arrest (OR,4.52; 95% CI, 2.63–7.64; P < 0.001), congestive heart failure (OR, 10.25; 95% CI, 7.86–13.40; P < 0.001), and stroke (OR, 3.06; 95% CI, 2.62–4.31; P < 0.001) compared with patients who did not develop PMI (Table 4). The overall mortality was 3.15% (Figure 1). The 30-day and 1-year mortality for surgical patients with and without PMI was shown in Figures 2, 3. The 30-day (0.96 vs.0.35%; OR 3.46; 95% CI, 1.49–7.98; P < 0.001) and 1-year mortalities (5.37 vs. 2.60%; OR 2.35; 95% CI, 1.12–6.53; P < 0.001) were significantly higher in patients who developed PMI compared with those who did not develop PMI.

Patients were prescribed with low molecular heparin in 18.13% of cases, antiplatelet therapy in 30.7% of cases, oral anticoagulation in 9.42%, an angiotensin-converting enzyme (ACE) inhibitor in 19.7%, a statin in 34.75%, and a beta-blocker in 11.16%. As shown in Table 5, patients who developed PMI were more likely to have received low molecular heparin, anti-plantlet therapy, beta-blocker, early coronary angiography, and statin than patients who did not develop PMI. There were no differences in the prescribing frequency of Angiotensin-converting-enzyme inhibitors (ACEI)/ angiotensin II receptor blockers (ARB) , oral anticoagulation. Overall, low molecular heparin was prescribed in 31.05% (130/418) of PMI cases. Dalteparin sodium 2,500 IU was injected subcutaneously every 12 h. The incidence of major bleeding was 15.38% (20/130) in the entire group. However, four (3.07%, 4/130) patients, who received low molecular heparin therapy, died of massive hemorrhage of the gastrointestinal tract, all of them suffered from acute myocardial infarction.

In this retrospective study of 2,984 patients 80 years of age or older undergoing non-cardiac surgery, the incidence of PMI was 14%, which was higher than that seen in a large national database (8%) (3). The 30-day mortality was 0.43%, which was much lower than that seen in other studies (11, 12). The observed 30-day mortality after surgery ranges between 1 and 10% (3, 12–17).

Approximately 50% of PMI occurs on the day of surgery, and 18% on the second postoperative day. Only 22% of patients with PMI fulfilled the universal definition of myocardial infarction. A minority (9.57%) of patients suffering PMI experienced an ischemic feature. Any ischemic ECG changes were presented in 76.56% of patients with PMI. Therefore, nearly 90% of PMI would, probably, have gone undetected without systematic troponin and ECG monitoring after surgery. Patients with PMI had a greater burden of cardiovascular events than patients without PMI. In comprehensive elevations of cardiac troponin in combination with ischemic symptoms, ECG changes are helpful to identify PMI.

The combination of aging and multi-comorbidities, such as cardiovascular disorders or renal insufficiency, is the principal factor increasing surgical stress in older patients. The elderly patient who undergoes surgery has decreased ability to compensate and maintain homeostasis when the body is stressed. The perioperative management of old patients with multiple conditions is a great challenge for hospital physicians.

The perioperative risk of patients is markedly increased due to the cardiac condition itself and co-morbidities. In the present study, multivariable analyses showed that coronary artery disease, chronic heart failure, and hypotension were independently associated with the development of PMI. Co-management model by surgeons and geriatricians is helpful with perioperative management of cardiovascular complications and has the potential to improve outcomes. In our study, the incidence of PMI was higher and the 30-day mortality was lower than that seen in other studies (11, 12). A system review showed orthogeriatric collaboration to improve mortality after hip repair (18). One recent meta-analysis demonstrated that orthogeriatric care models reduced length of stay, in-hospital mortality, 1-year mortality, and delirium of patients with hip fracture and may reduce complications and cost (19).

The PMI is a complex syndrome with multiple different underlying etiologies, including type 1 myocardial infarction (T1MI), and emphasis on the causal relationship of plaque disruption with coronary atherothrombosis; while in type 2 myocardial infarction (T2MI), settings with oxygen demand and supply imbalance are unrelated to acute coronary atherothrombosis (6). The PMIs, after non-cardiac surgery, are largely considered type 2 infarction. The OPTIMUS and Coronary CTA VISION Studies showed that, at most, a quarter to a third of PMIs are due to thrombosis, whereas at least two-thirds to three-quarters are likely due to supply-demand mismatch (20, 21). In the present study, 22% of patients with PMI fulfilled the universal definition of myocardial infarction. A patient with a history of previous coronary artery disease merits special attention as it is a strong predictor of PMI. Given the super old age and higher prevalence of concomitant coronary artery disease in a series of patients with PMI, we suggest consideration of non-invasive evaluation for ischemia if appropriate. The risk and benefit of coronary interventions should be taken into account more cautiously in patients, who are at risk of bleeding shortly after surgery, because withdrawing antiplatelet therapy may lead to in-stent thrombosis (22, 23).

Another issue of perioperative risk is bleeding (24). Of note, 31.05% of patients with PMI received therapy of low molecular weight heparin (LMWH). The median duration of postoperative LMWH administration was 7 days. The incidence of major bleeding was 15.38% and 30-day mortality was 3.07%. Management of anticoagulation during invasive procedures varies widely and remains challenging and controversial. Based on these findings, it was concluded that LMWH should be used to decrease the risk of thromboembolic events without increasing the risk of bleeding. The risks of bleeding for any surgical procedure must be weighed against the benefit of remaining on anticoagulants on a case-by-case basis.

The optimal management of patients with PMI remains an area of the ongoing investigation. A multidisciplinary approach and expert guidance on the assessment and medical management of multi-morbidity, pump flow control, hemodynamic monitoring, anticoagulation strategies, infection, and bleeding prevention strategies are considered important. Appropriate use of intravenous fluids to maintain fluid and electrolyte balance is important for normal organ function after surgery. Optimal perioperative medical therapy should be adopted for the prevention and management of PMI, including antiplatelet agents, β-Blocker (25–29), statins (12, 30–34), ACE inhibitors, and anticoagulants. These patients can benefit from intensification of assessment and medical management of multi-morbidity during the perioperative period (35).

The main strength of the present study is that it includes a large sample of surgical patients aged over 80 years, which allowed us to demonstrate the incidence and prognosis of the PMI diagnosis in elderly surgical patients, to show the advantage of the co-management model by geriatricians and surgeons in mortality. There are several limitations of this study. First, this study was a retrospective study, excluding patients without troponin T measurement, thus, leading to a remarkable risk of selection bias. Second, the effects of troponin levels on outcomes were not analyzed. Third, the subjects were from a single health center and most of them were male.