Diagnosis of myocardial infarction

12-lead EKG showing ST elevation, indicative of myocardial infarction

The diagnosis of myocardial infarction (MI), commonly known as a heart attack, involves a combination of clinical evaluation, electrocardiogram (ECG) findings, and laboratory tests. Myocardial infarction occurs when blood flow to a part of the heart is blocked for a long enough time that part of the heart muscle is damaged or dies.

Clinical Presentation

Patients with myocardial infarction typically present with chest pain or discomfort, which may radiate to the arms, neck, jaw, or back. Other symptoms can include shortness of breath, nausea, vomiting, palpitations, and sweating. It is important to note that some patients, particularly women, the elderly, and those with diabetes, may present with atypical symptoms or even be asymptomatic.

Electrocardiogram (ECG)

The ECG is a critical tool in the diagnosis of myocardial infarction. It can show characteristic changes such as ST-segment elevation, T-wave inversion, and the development of pathological Q waves. These changes help differentiate between ST-elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTEMI).

Biomarkers

Cardiac biomarkers are substances that are released into the blood when the heart is damaged. The most commonly used biomarkers for diagnosing myocardial infarction are troponin I and T, which are highly specific to cardiac tissue. Elevated levels of these biomarkers indicate myocardial injury.

Imaging

Histopathological image showing myocardial infarction with contraction bands

Imaging techniques such as echocardiography and coronary angiography can be used to assess the extent of myocardial damage and to identify the location and severity of coronary artery blockages. Echocardiography can also help evaluate heart function and detect complications such as heart failure or ventricular septal defect.

Pathology

Histopathology of myocardial infarction showing contraction bands

Pathological examination of myocardial tissue can reveal changes characteristic of infarction, such as coagulative necrosis, contraction band necrosis, and inflammatory cell infiltration. Gross pathology may show areas of pallor or hemorrhage in the heart muscle.

File:Gross pathology of a one week old myocardial infarction with focal rupture.jpg

Gross pathology of a one-week-old myocardial infarction with focal rupture

Differential Diagnosis

The differential diagnosis of myocardial infarction includes other causes of chest pain such as angina pectoris, pericarditis, aortic dissection, and pulmonary embolism. It is crucial to distinguish these conditions as they require different management strategies.

Related Pages

• Coronary artery disease
• Heart failure
• Cardiac arrest
• Cardiovascular disease