What is the diagnostic approach for a myocardial infarction (MI)?

From the Guidelines

The diagnostic approach for myocardial infarction (MI) should involve a combination of clinical evaluation, cardiac biomarkers, and imaging studies, with a focus on high-sensitivity troponin assays and rapid "rule-in" and "rule-out" algorithms, as recommended by the 2020 ESC guidelines for the management of acute coronary syndromes in patients presenting without persistent ST-segment elevation 1. When a patient presents with symptoms suggestive of MI, such as chest pain, shortness of breath, or diaphoresis, the first step is to obtain a 12-lead electrocardiogram (ECG) within 10 minutes of arrival. The ECG may show ST-segment elevation, ST-segment depression, T-wave inversions, or new left bundle branch block. Blood tests for cardiac biomarkers, particularly troponin I or T, should be drawn immediately and then repeated at 1-2 hours, using the 0 h/1 h or 0 h/2 h algorithm, which allows for a minimal sensitivity and NPV of 99% and a minimal PPV of 70% 1. A significant rise and/or fall in troponin levels with at least one value above the 99th percentile upper reference limit confirms myocardial injury. Additional diagnostic tools include echocardiography to assess wall motion abnormalities and cardiac function, and coronary angiography to visualize coronary artery occlusions. In cases where the diagnosis remains uncertain, cardiac MRI or CT angiography may be employed. While awaiting diagnostic confirmation, treatment should begin immediately with aspirin 325 mg chewed, supplemental oxygen if saturation is below 90%, and pain management with nitroglycerin and morphine if needed, as timely reperfusion therapy significantly improves outcomes, with the goal of door-to-balloon time under 90 minutes for primary percutaneous coronary intervention in STEMI cases. It is essential to consider the clinical context and other factors that may affect troponin concentrations, such as age, renal dysfunction, and chest pain onset, as highlighted in the 2020 ESC guidelines 1. The use of high-sensitivity troponin assays and rapid diagnostic algorithms can help improve the accuracy and efficiency of MI diagnosis, ultimately leading to better patient outcomes. Key points to consider in the diagnostic approach for MI include:

• The use of high-sensitivity troponin assays as the preferred biomarker for myocardial damage 1
• The implementation of rapid "rule-in" and "rule-out" algorithms, such as the 0 h/1 h or 0 h/2 h algorithm, to minimize sensitivity and NPV of 99% and a minimal PPV of 70% 1
• The consideration of clinical context and other factors that may affect troponin concentrations, such as age, renal dysfunction, and chest pain onset 1
• The importance of timely reperfusion therapy and door-to-balloon time under 90 minutes for primary percutaneous coronary intervention in STEMI cases.

From the Research

Diagnostic Approach for Myocardial Infarction (MI)

The diagnostic approach for myocardial infarction (MI) involves several steps and tools, including:

• Detection of cardiac troponin elevation >99th percentile, which is a key indicator of acute myocardial infarction (AMI) 2
• Use of the 12-lead electrocardiogram (ECG) to guide management in patients with suspected MI, including the identification of subtle features suggestive of ischemia 3
• Integration of clinical presentation and ECG findings to diagnose coronary occlusion MIs
• Application of rules such as the modified Sgarbossa criteria to identify acute MI in left bundle branch block or ventricular pacing 3

Diagnostic Tools and Techniques

Some of the diagnostic tools and techniques used in the diagnosis of MI include:

• Electrocardiogram (ECG) to detect ST-segment elevation or depression, which can indicate the presence of an MI 3, 4
• Troponin testing to detect elevated troponin levels, which can indicate the presence of an MI 2
• Echocardiography (ECHO) to evaluate cardiac function and detect any abnormalities 2
• Coronary angiography (CAG) to visualize the coronary arteries and detect any blockages 2

Management and Treatment

The management and treatment of MI involve several strategies, including:

• Use of antiplatelet agents, such as aspirin and clopidogrel, to prevent further clotting 5, 6
• Use of anticoagulants, such as heparin and low-molecular-weight heparin, to prevent further clotting 5, 6
• Percutaneous coronary intervention (PCI) with stent placement to restore blood flow to the affected area 5
• Fibrinolytic therapy to dissolve clots and restore blood flow to the affected area 5
• Coronary artery bypass grafting (CABG) to bypass blocked coronary arteries and restore blood flow to the affected area 5