Perioperative myocardial injury in non-cardiac surgery - incidence, patient characteristics, outcome, and possible strategies to improve outcome

The global volume of surgery is steadily increasing and surgical patients are becoming older and increasingly comorbid, making the perioperative setting a common challenge for physicians. Despite substantial improvements in surgical and anaesthesiological techniques, there is still a relevant risk of dying associated with non-cardiac surgery, with 30-day mortality rates ranging from 1 to 10% depending on the patient population.
Major cardiac complications are believed to be a major contributor to this excessive mortality. In particular, perioperative myocardial injury (PMI) appears to be a major contributor and is potentially associated with one third of postoperative mortality. Initial study data have highlighted that PMI is difficult to diagnose, as typical symptoms of spontaneous acute myocardial infarction, especially ischemic chest pain, are only observed in <20% of all patients.
In order to address important gaps in knowledge of PMI, we conducted my PhD project “Perioperative Myocardial Injury in Non-cardiac Surgery – Incidence, Patient Characteristics, Outcome and Possible Strategies to Improve Outcome“ (BASEL-PMI) at the University Hospital Basel. Its aim was to generate data within clinical routine to gain important insights into the incidence of PMI, its association with postoperative mortality, and to further characterise PMI.
We were able to show that PMI is surprisingly common after non-cardiac surgery, occurring in 16% or in one in seven patients. With a mortality rate within 30 days of 10% and of 23% within one year, the associated mortality increased six-fold in comparison to patients without a PMI (1.6% at 30 days, 9.3% within one year), highlighting the importance of PMI as a perioperative complication. Nonetheless, due to their asymptomatic presentation (2/3 did not show any signs or symptoms), PMI are often missed in clinical routine. This lack of appreciation of a significant postoperative complication compromises the prognostic accuracy of preoperative scores used to assess the risk-benefit of surgery.
In characterising PMI, we were able to identify two distinct subcategories of PMI, separating a “cardiac” subtype from an “extra-cardiac” subtype in which the heart is damaged by a systemic pathology such as severe sepsis. Furthermore, we were able to show that PMI is associated with an increased mortality independent of the ischemic symptoms or of whether the signs are present or not (8.7% vs 10.4%).
Finally, we made our first tentative steps towards the hypothesis that systematic screening for PMI might improve outcome.