Clinical Characteristics and Functional Outcomes of Postoperative Myocardial Injury: a Prospective Cohort Study. TEAMS (Troponin Elevation After Major Surgery) Study

Background to main study question: Cardiac complications are a common cause of morbidity after non-cardiac surgery. Patients with perioperative myocardial injury (both MI, and lower levels of cardiac troponin elevation) experience higher short-term and long-term mortality. They are also at substantially increased risk of additional cardiac and non-cardiac complications. It is therefore plausible that myocardial injury adversely affects quality of life. This study will compare postoperative health-related quality of life of patients who did or did not experience perioperative myocardial injury (defined by troponin-I > 0.07ng/ml) after non-cardiac surgery

Study Design: Pilot prospective cohort study (n = 300). Population: Consecutive patients undergoing non-cardiac, non-transplant surgery at UHN.

Background to secondary study questions:

1. Clinically based risk stratification tools used in non-cardiac surgery (e.g., Revised Cardiac Risk Index) are of moderate utility and assign patients only to broad risk categories. This study will examine the usefulness of pre-operative biomarkers (BNP, HbA1c, and others) in supporting cardiac risk stratification and will address the question: Is there a set of preoperative criteria that can accurately inform the decision to monitor troponin postoperatively?
2. Intra-operative physiological derangement measured with the Surgical Apgar Score correlates with morbidity and mortality 3-months postoperatively. This study will examine the relationship between the Surgical Apgar Score; continuous non-invasively monitored intraoperative metrics of hemoglobin concentration and occult hypovolemia (Pleth Variability Index) with the Masimo Radical-7 Pulse Co-Oximeter; and the primary and secondary outcomes. This aspect of the study will address the question: Can readily available intraoperative physiological data inform the decision to monitor troponin postoperatively?
3. Quality of Recovery-40 Score evaluates (in the recovery room and at 24 hours postoperatively) the patient's subjective experience of their recovery from surgery. This metric is correlated with quality of life 3-months postop. This study will evaluate correlation between Quality of Recovery-15 Score, a valid and more efficient means of measuring recovery, and the primary and secondary outcomes.
4. Approximately 2/3 of patients who have postoperative myocardial injury are asymptomatic and have no ECG changes. Diagnosis of MI requires biomarker elevation (Troponin > 0.3ng/ml) plus clinical or ECG or imaging evidence of myocardial injury. Of the latter 3 criteria, 2 are often absent. In selected patients, this study will use trans-thoracic echocardiography, CT coronary angiography, and cardiac MRI to improve diagnostic yield and define those diagnostic modalities that are most useful in the postoperative patient.

Rationale:

Postoperative myocardial injury may negatively impact health-related quality of life. Affected patients may experience higher levels of postoperative dependency. This possibility has implications for patient rehabilitation, provincial and personal healthcare costs, as well as patients' physical, emotional and mental well-being and relationships. The public health dimension of this problem could therefore be significant. In addition, an incomplete understanding exists of how individual patient cardiac risk factors, in combination with the perioperative environment, result in myocardial injury. The diagnostic investigations that are most useful in this setting have not yet been clearly defined. Patients who fail to be rescued after experiencing postoperative complications (as distinct from failure to avoid experiencing the complication in the first instance) plays a central role in postoperative mortality. Early recognition of such patients is therefore crucial. By prospectively observing a cohort of high-risk surgical patients, this study will provide insight into how these factors interact. This will allow us to better characterize the potential predictors and features of postoperative myocardial injury. We hope that our findings will aid in the identification of patient characteristics associated with increased risks of postoperative myocardial injury, thus helping to direct diagnosis, early treatment and rescue. This study will thus potentially yield important data that will positively impact future patient care and the rational use of healthcare resources.