30th May 2026

Non-ST Elevation Myocardial Infarction (NSTEMI)

Background

Non-ST elevation myocardial infarction (NSTEMI) is an acute ischemic event causing myocyte necrosis, detected by troponin elevation. It can be distinguished from unstable angina by a dynamic elevation of troponin above the 99th percentile. The ECG may show ischemic changes (e.g., ST depression, T-wave changes), but it can also be normal or show non-specific changes.

Key Difference from Unstable Angina: NSTEMI involves troponin elevation, while unstable angina does not.

Epidemiology

NSTEMI incidence is rising due to improved diagnostics, early pharmacotherapy, and better STEMI prevention.

Aetiology & Pathophysiology

NSTEMI results from oxygen supply-demand imbalance, often due to non-occlusive thrombus from plaque rupture, vasospasm, or other factors. Severity depends on ischemia duration, collateral flow, and comorbidities. Key features include plaque rupture at thin cap regions, with occlusions often arising from lesions <50% stenotic.

Diagnosis

Investigations

• ECG: 12-lead within 10 minutes; may show ST depression, T-wave inversion, or transient ST elevation.
• Troponin: Dynamic elevation confirms NSTEMI. 
  • Diagnosis requires rise/fall with ≥99th percentile value.
  • Use rapid rule-in/rule-out algorithms (ESC 0/1h or 0/3h) where validated.
  • Large elevations (>5× URL) indicate acute Type-1 MI and higher risk.
• Other tests: Chest X-ray, blood tests (FBC, U&E, LFTs, glucose, CRP), and echocardiography if heart failure or instability is suspected.
• Risk Pathways: Use troponin levels and repeat testing to guide management.

Clinical Manifestations

Chest pain >15 minutes, new/worsened, accompanied by nausea, sweating, breathlessness, or hemodynamic instability. Risk factors include diabetes, renal dysfunction, hypertension, smoking, a family history of coronary artery disease, a sedentary lifestyle, and obesity. Red flags include hemodynamic instability, acute LV failure, or arrhythmias.

Management

• Initial Treatment: Aspirin, sublingual GTN, morphine, oxygen (if SpO₂ <90%).
• Anticoagulation: Fondaparinux or heparin.
• Urgent Coronary Angiography (ICA): For unstable patients or those with high-risk features (ongoing pain, instability, arrhythmias, high-risk comorbidities, or high-risk stratification scores).
• Long-term Treatment: Dual antiplatelet therapy (for at least 12 months), beta-blockers, ACE inhibitors/ARBs, statins, aldosterone antagonists (for HF), and SGLT2 inhibitors (for HF).

Prevention & Follow-Up

• Primary Prevention: Smoking cessation, healthy diet, regular physical activity, and statin therapy for high-risk individuals.
• Secondary Prevention: Lifestyle changes, cardiac rehab, and long-term medication adherence.
• Obesity is a significant modifiable risk factor, and weight management and lifestyle modification are key to reducing the risk of future cardiovascular events. 
• Smoking is also known to be a well-established risk factor linked to recurrent cardiovascular events, and smoking cessation should be encouraged in all patients.
• Follow-up: Outpatient visit 1-2 weeks post-discharge, lipid monitoring every 6 months, and regular medication reviews.

Complications

• Short-term: Cardiac arrhythmias, acute heart failure, cardiogenic shock, acute mitral regurgitation, post-MI pericarditis, venous thromboembolism (VTE).
• Variable: Depression, in-stent thrombosis.

Prognosis

NSTEMI patients face high morbidity and mortality risks, with a 4-6 times higher risk of sudden death than the general population. Key risk factors include diabetes, smoking, heart failure, and infarct extent. Modern treatments (statins, revascularisation) reduce mortality, but age and other factors temper the benefits. Cardiovascular death risk post-MI is about 10% in the first year, with lifestyle changes and cardiac rehab improving survival.