How to Manage PMI? – Practical Implementation in Ramathibodi Hospital

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Q1. What is perioperative myocardial injury (PMI), and how does it differ from AMI?

PMI refers to myocardial injury detected by an elevation in cardiac troponin following non-cardiac surgery, typically within the first 48 hours. Unlike AMI, PMI does not require ischemic symptoms, ECG changes, or angiographic evidence of plaque rupture. It reflects myocardial stress or injury of varying severity, often related to supply–demand mismatch, hemodynamic instability, anemia, or perioperative stress. Importantly, PMI should be viewed as a risk signal, not automatically as an indication for emergent coronary intervention. [2] 

Q2. Why is cardiac troponin useful beyond diagnosing acute MI?

High-sensitivity cardiac troponin (hs-cTn) is highly sensitive for detecting myocardial injury, even at low levels. Troponin can be released not only with irreversible cardiomyocyte necrosis but also with reversible injury or cellular stress, through mechanisms such as membrane blebbing. As a result, modest troponin elevations may occur in a range of conditions, including hypertension, chronic kidney disease, or perioperative stress, yet still carry important prognostic information. This makes hs-cTn a valuable screening and risk-stratification tool, not just a diagnostic test for AMI. [1,2] 

Q3. How common is PMI, and why is it frequently missed?

Large observational data and real-world experience demonstrate that PMI is common and under-recognised. Approximately 80% of PMI cases are asymptomatic, meaning they would be missed without routine biomarker monitoring. Despite the absence of symptoms, PMI is associated with a significantly higher 30-day mortality compared with patients without PMI. Notably, outcomes are similar in symptomatic and asymptomatic PMI, underscoring that the absence of chest pain does not imply low risk. [2,4] 

Q4. What do current guidelines recommend regarding perioperative troponin monitoring?

Contemporary guidelines increasingly support the routine use of perioperative cardiac biomarkers in selected surgical patients. The 2022 ESC guidelines go further, issuing a Class I recommendation for both preoperative and postoperative high-sensitivity cardiac troponin testing in patients aged ≥65 years or those with cardiovascular risk factors or known ASCVD undergoing intermediate- or high-risk noncardiac surgery. Together, these recommendations reposition troponin from a reactive diagnostic test to a proactive tool for perioperative risk assessment. [1] 

Q5. How was PMI surveillance implemented at Ramathibodi Hospital?

At Ramathibodi Hospital, perioperative myocardial injury surveillance was implemented using a pragmatic, workflow-adapted protocol that integrated seamlessly into routine care. High-sensitivity cardiac troponin T is measured preoperatively to establish baseline risk, followed by postoperative testing on Day 1 and Day 2 rather than strict 24- and 48-hour intervals, thereby avoiding overnight disruptions. A rise in hs-cTn above 14 ng/L is used to define PMI. Surgeons and anesthesiologists initiate testing, nurses manage sampling, laboratories flag abnormal results, and internal medicine teams provide first-line clinical review, with cardiology consultation reserved for patients with ST-elevation MI or other high-risk features. This approach enables timely detection while limiting unnecessary escalation. [4] 

Q6. What were the key findings from Ramathibodi Hospital’s real-world data?

Real-world data from Ramathibodi Hospital closely mirrored international observations. PMI occurred in approximately 10% of monitored patients, with a mean age of around 71 years. In most cases (about 80%), individuals were asymptomatic. Despite this, 30-day mortality was substantially higher in patients with PMI, at approximately 9%, compared with around 1% in those without PMI. These findings reinforced PMI as a clinically meaningful risk state in routine surgical populations. [4] 

Q7. How should patients with PMI be managed in practice?

In practice, PMI management prioritizes risk optimisation over reflexive, invasive intervention. Patients without ischemic symptoms are managed similarly to those with a positive stress test, with attention directed toward identifying and correcting reversible contributors such as anemia, infection, or hemodynamic instability. Preventive therapies, including statins or antiplatelet agents, are initiated or optimised when appropriate, and structured outpatient follow-up with further cardiac evaluation is arranged as needed. Invasive coronary assessment is reserved for patients with clear high-risk features, thereby balancing patient safety with responsible resource use.[1,3] 

Q8. What are the key lessons for hospitals considering PMI implementation?

Successful PMI surveillance requires a shift in mindset, recognising myocardial injury detection as an opportunity for earlier intervention rather than an added burden. Implementation depends on close multidisciplinary collaboration among surgery, anesthesia, nursing, laboratory services, and internal medicine, as well as on the thoughtful adaptation of guideline recommendations to local staffing, infrastructure, and workflow realities. When implemented effectively, PMI detection enables earlier identification of vulnerable patients and has the potential to meaningfully improve perioperative outcomes. [4]