ACUTE CORONARY SYNDROME

By: J. de la Cruz

Aim:

 To explain perioperative cardiac complications.  

Background: 

Acute coronary syndromes (ACS) represent a medical emergency where heart muscle is starved of oxygen due to sudden coronary artery blockage. Symptoms  are subjective such as classic chest pain, but can be subtle: dyspnoea (laboured breathing) , nausea, and  jaw pain.

In perioperative settings, they can emerge unexpectedly, turning a routine procedure into a crisis.

ACS includes

• Unstable angina- ECG can be normal or show ischaemic changes such as ST depression or T‑wave inversion

•  non-ST-elevation myocardial infarction (NSTEMI) -ECG may show ST depression, T‑wave inversion, or be nonspecific. 

  
  

• ST-elevation MI (STEMI) -New ST‑segment elevation 

Diagnosis of ACS depends on the results from : ECG trace, troponin blood marker, and clinical context. Troponin confirms if heart muscle cells have ruptured, spilling proteins into blood after >20-30 minutes of myocardial ischaemia (MI). The 2025 Australian guideline stresses rapid troponin testing and ECG . 

Perioperative Relevance

Surgery stresses the heart through haemodynamic  shifts, inflammation, anaemia, and tachycardia. Patients with recent ACS (<30 days) have 5-10x higher perioperative MI risk; even stable coronary artery disease (CAD) elevates it 2-3x. Non-cardiac surgery can provoke plaque rupture via demand-supply mismatch. This mismatch happens when your heart muscle suddenly doesn't get enough oxygen-rich blood to keep up with its workload

ACS example scenarios:

​An elderly patient post orthopaedic surgery was stable intraoperatively. Post operatively, pt is sweaty, short of breath, with a  BP 90/60, HR 120. Initial ECG shows subtle ST depression in the ECG trace, and positive  troponin with blood test. This  suggests perioperative NSTEMI from surgical stress on the undiagnosed coronary artery disease. 

A patient with hypertension, undergoes emergency laparotomy for bowel obstruction. Midway, the patient develops ventricular ectopics, ST elevation with hypotension and positive troponin blood test result. It is likely to be STEMI. 

References:

Australian Institute of Health and Welfare (2025), https://www.aihw.gov.au/reports/heart-stroke-vascular-diseases/hsvd-facts/contents/all-heart-stroke-and-vascular-disease/coronary-heart-disease?gh_jid=5059341003

Mahendran, S., Thiagalingam, A., Hillis, G., Halliwell, R., Pleass, H. C., & Chow, C. K. (2023). Cardiovascular risk management in the peri‐operative setting. Medical Journal of Australia, 219(1). https://onlinelibrary.wiley.com/doi/pdf/10.5694/mja2.51988

National Heart Foundation of Australia & Cardiac Society of Australia and New Zealand. (2025). Australian clinical guideline for diagnosing and managing acute coronary syndromes 2025. https://www.heartfoundation.org.au/for-professionals/acs-guideline

DISCLAIMER:

The information presented here is provided for general educational and informational purposes only. It does not constitute medical advice and is not a clinical protocol. Readers must always refer to their institutional policies and clinical guidelines and consult with qualified healthcare professionals for individual patient care. The author and this site disclaim any liability for adverse outcomes that may result from the use or application of the information provided.