ECGs in Acute Myocardial Infarction

Acute myocardial infarction is myocardial necrosis that results from acute obstruction of a coronary artery. The symptoms include chest discomfort with or without dyspnea, diaphoresis, and nausea. The diagnosis is performed using electrocardiography (ECG) and the presence or absence of biomarkers. 

In the United States, it is a common sight to witness 1.0 million myocardial infarctions every year. It results in the deaths of 300,000 to 400,000 people. It is crucial to diagnose an myocardial infarction ECG because of the stakes involved for the patient. One of the complications is it is difficult to ascertain the changes that are new and old. Keep reading to explore more about ECGs in acute myocardial infarction.

What are the ECGs in acute myocardial infarction?

Here are the ECGs in acute myocardial infarction:

1. Acute coronary syndrome: Acute coronary syndrome includes various clinical entities, including infarction or ischemia. The syndrome includes unstable angina, non-ST segment elevation myocardial infarction, and ST segment elevation myocardial infarction (STEMI). Non-ST segment elevation myocardial infarction is referred to as a non-Q wave myocardial infarction. On the contrary, STEMI is referred to as a Q-wave myocardial infarction. This is because ST segment elevation myocardial infarction is associated with a pathological Q wave.
2. Myocardial infarction: For a patient to be diagnosed with myocardial infarction, you must meet two of the following three criteria: This is according to the World Health Organization. Here are the following criteria:

• Clinical history of chest discomfort consistent with ischemia, including crushing chest pain.
• Elevation of cardiac markers in the blood.
• Characteristic changes on electrocardiographic tracings taken serially.

It is crucial to compare the current ECG of the patient with an old ECG. On the other hand, treat the changes with ECG if the prior ECG is not available.

1. Pathological Q Waves: A pathological Q wave is more than 0.04 seconds in duration. More than 25% of the size of the following R waves is in that lead. As pathological Q waves may take hours to develop and can often act long, the presence of new pathological Q waves indicates acute myocardial infarction.
2. ST segment changes: One of the most crucial findings of myocardial infarction is the presence of ST segment elevation. This segment is part of ECG training. This starts where the S wave finishes and ends where the T wave begins. The point where the end of the wave and ST segment meet is known as the J point. If the J point is greater than 2mm, then it is inconsistent with an ST segment elevation myocardial infarction.

In the acute phase of non-ST segment elevation myocardial infarction, the ST segment is depressed in leads that face the compromised portion of the heart. It is challenging to diagnose a non-ST segment elevation myocardial infarction by ECG alone. It treats patients, and a diagnosis is made when the level of serum cardiac markers rises over several hours.

Read More: ECG Waves Explained: A Beginner’s Guide

What is the ischemic lesion?

A 12-lead ECG helps determine the coronary artery, which is likely affected by a chemical event. Leads II, III, and an aVF offer a view of the right coronary artery. The primary changes in ECG involve three leads. This suggests a problem in the right coronary. On the other hand, aVL, I, and V1 through V6 offer information about the left coronary artery.

Experienced users can understand the ECG tracing and localize damage to a few areas of the heart. The inferior wall of the heart is not compromised when there are active changes in leads II, III, and aVF. If there are abnormalities in leads V3 and V4, it suggests a problem in the interior wall of the heart. Leads V1 and V2 offer information about the cardiac septum.

For every active change, such as point elevation, there will be reciprocal changes in the complementary leads. This is opposite the affected area and suggests a problem in the left anterior infarct ECG descending artery. It affects the ventricular septum. It is expected to cause reciprocal changes in leads II, III, and aVF.

Read More: What Are The H’s and T’s of ACLS?

 

What are the ECG changes during myocardial infarction?

 

Location of MI	Leads affected	Vessel involved	Egg changes
Anterior wall	V2 to V4	Left Anterior Descending artery (LAD) – Diagonal branch	Progression of poor R-wave  T-wave inversion  ST-segment elevation
Septal infarct ECG wall	V1 and V2	Left Anterior Descending artery (LAD) – Septal branch	ST-segment rises  R-wave disappears  T-wave inverts
Lateral wall	I, aVL, V5, V6	Left Coronary Artery (LCA) – Circumflex branch	ST-segment elevation
Inferior wall	II, III, aVF	Right Coronary Artery (RCA) – Posterior descending branch	T-wave inversion  ST-segment elevation
Posterior wall	Vi to V4	Left Coronary Artery (LCA) – Circumflex branch Right Coronary Artery (RCA) – Posterior descending branch	Tall R waves  ST-segment depression  Upright T waves

 

Conclusion

ECGs are crucial to diagnosing acute myocardial infarction. This offers crucial insights into the functioning of the heart. Timely interpretation of ECG changes guides immediate treatment and improves outcomes. It is crucial to master ECG interpretation to manage and treat heart attack patients.