What are the diagnostic criteria for Non-ST-Elevation Myocardial Infarction (NSTEMI)?

From the Guidelines

Non-ST-Elevation Myocardial Infarction (NSTEMI) is diagnosed based on a combination of clinical presentation, cardiac biomarkers, and electrocardiogram (ECG) findings, with elevated cardiac troponin levels above the 99th percentile upper reference limit being a key criterion, as recommended by the 2020 ESC guidelines 1. The primary diagnostic criteria for NSTEMI include:

• Elevated cardiac troponin levels (either troponin I or T) above the 99th percentile upper reference limit
• Symptoms of myocardial ischemia (typically chest pain, pressure, or discomfort)
• New ECG changes (such as ST-segment depression, T-wave inversion, or nonspecific ST-T wave changes)
• Development of pathological Q waves on ECG
• Imaging evidence of new loss of viable myocardium or regional wall motion abnormality
• Identification of intracoronary thrombus by angiography It is essential to note that NSTEMI differs from STEMI by the absence of ST-segment elevation on the ECG, as highlighted in the 2014 AHA/ACC guideline 1. Serial troponin measurements are often necessary, typically at presentation and 3-6 hours later, to detect a rise and/or fall in levels, and high-sensitivity troponin assays have improved early detection, as stated in the 2020 ESC guidelines 1. Other biomarkers like CK-MB have largely been replaced by troponin due to superior cardiac specificity. The diagnosis should be made in the context of the patient's clinical presentation, as troponin elevation can occur in conditions other than acute coronary syndrome, such as myocarditis, pulmonary embolism, or renal failure, as noted in the 2014 AHA/ACC guideline 1. The 2020 ESC guidelines recommend an immediate invasive strategy in patients with very high-risk criteria, such as haemodynamic instability or recurrent chest pain, and an early invasive strategy within 24 hours in patients with high-risk criteria, such as diagnosis of NSTEMI suggested by the diagnostic algorithm or dynamic ST/T-segment changes 1.

From the Research

Diagnostic Criteria for NSTEMI

The diagnostic criteria for Non-ST-Elevation Myocardial Infarction (NSTEMI) include:

• Elevated cardiac biomarkers of necrosis, such as troponin, in the absence of persistent ST-segment elevation on an electrocardiogram (ECG) 2
• Presence of anginal symptoms or other acute events 2
• Myocardial oxygen supply and demand mismatch, which can be caused by various factors, including acute atherothrombotic events or other conditions 2

Types of NSTEMI

There are two types of NSTEMI:

• Type 1: caused by an acute atherothrombotic event 2
• Type 2: caused by other factors that lead to a mismatch of myocardial oxygen supply and demand 2

Risk Stratification and Management

Risk stratification is essential in managing NSTEMI patients, and treatment should be based on individualized patient risk assessment 2. The management of NSTEMI includes:

• Anti-anginal therapy, such as nitrates and beta-blockers 3
• Anticoagulant and antiplatelet therapy, such as aspirin and P2Y12 inhibitors 3, 4, 5
• Revascularization procedures, such as percutaneous coronary intervention (PCI) 3, 5
• Secondary prevention therapies, such as statins and angiotensin-converting enzyme inhibitors, to reduce the risk of recurrent events 5

Challenges in NSTEMI Management

Despite the availability of guidelines and evidence-based treatments, there are still challenges in managing NSTEMI patients, including:

• Variability in treatment practices and delays in administration of medications 6
• Higher risk of complications and recurrent events in certain patient populations, such as those with diabetes 5
• Need for ongoing quality improvement efforts to optimize patient outcomes 6