Learning Objectives 🎯

• 💡 Review key ECG findings related to ischemia, injury, and infarction.
• 📝 Identify different types of ACS based on ECG changes.
• 📚 Differentiate between STEMI, NSTEMI, and unstable angina on an ECG.
• 📈 Interpret ECGs to recognize reciprocal changes.
• ❓ Apply your knowledge to answer ACS-related quiz questions.

Step-by-Step Content 📝

Review of Key ECG Findings 🔍

Before diving into ACS, let’s recap essential ECG findings:

• Ischemia: T wave inversion or ST-segment depression. 💔
• Injury: ST-segment elevation. 🔥
• Infarction: Presence of Q waves (significant Q waves are > 1/3 the height of the R wave, or >0.04 seconds wide).💀

Acute Coronary Syndrome (ACS) Explained 🚨

ACS encompasses a range of conditions associated with sudden, reduced blood flow to the heart. Key types include:

• STEMI (ST-Elevation Myocardial Infarction): Complete blockage of a coronary artery leading to ST-segment elevation on the ECG. Requires immediate intervention (e.g., PCI). 🚑
• NSTEMI (Non-ST-Elevation Myocardial Infarction): Partial blockage or severe narrowing of a coronary artery, often with ST-segment depression or T-wave inversion, but *without* ST-segment elevation. ⚠️
• Unstable Angina: Chest pain that is new in onset, increasing in frequency, or occurs at rest. ECG may show transient ST-segment depression or T-wave inversion. 😟 Cardiac enzymes will be normal.

ECG Clues for ACS Identification 🕵️‍♀️

Here’s how to differentiate between these ACS types on an ECG:

1. STEMI: Look for ST-segment elevation in contiguous leads (e.g., V1-V4 for anterior MI, II, III, aVF for inferior MI). Reciprocal changes (ST-segment depression) may be present in opposite leads.
2. NSTEMI: Look for ST-segment depression, T-wave inversion, or both. ST-segment elevation *should not* be present.
3. Unstable Angina: ECG may appear normal or show transient ST-segment depression or T-wave inversion. Repeat ECGs may be necessary.

Reciprocal Changes Explained 🔄

Reciprocal changes refer to ST-segment depression seen in leads opposite the site of ST-segment elevation. For example, if you see ST-elevation in leads II, III, and aVF (inferior MI), you might see ST-depression in leads I and aVL. Recognizing reciprocal changes helps confirm the location of the myocardial infarction.

Example ECG Interpretation 🩺

Imagine an ECG showing ST-segment elevation in leads II, III, and aVF. This indicates an inferior STEMI. You also notice ST-segment depression in leads I and aVL, which are reciprocal changes. This reinforces your diagnosis of an inferior STEMI and suggests potential involvement of the right ventricle.

Practical Exercise 🏋️‍♂️

Consider an ECG showing ST-segment depression in leads V1-V3 and prominent, upright T-waves. What type of ACS is most likely?

(Answer: Posterior MI. Look for reciprocal changes. V1-V3 are viewing the posterior wall.)

Quiz Time ❓

1. Which of the following ECG findings is MOST indicative of ischemia?
   A. ST-segment elevation
   B. Q waves
   C. T-wave inversion (Correct)
   D. Peaked T waves
2. ST-segment elevation in leads II, III, and aVF suggests which type of myocardial infarction?
   A. Anterior
   B. Lateral
   C. Inferior (Correct)
   D. Septal
3. Which type of ACS is characterized by complete blockage of a coronary artery and ST-segment elevation on the ECG?
   A. Unstable Angina
   B. NSTEMI
   C. STEMI (Correct)
   D. Stable Angina
4. Reciprocal changes in an ECG are characterized by:
   A. ST-segment elevation in all leads
   B. ST-segment depression in leads opposite the area of ST-segment elevation (Correct)
   C. Q waves in all leads
   D. T-wave inversion in all leads
5. An ECG showing ST-segment depression in leads V1-V3 with upright T waves may indicate:
   A. Anterior MI
   B. Inferior MI
   C. Posterior MI (Correct)
   D. Lateral MI

Correct answers in parentheses above.

Summary: Today, we reviewed key ECG findings related to ischemia, injury, and infarction, focusing on how these findings manifest in different types of ACS (STEMI, NSTEMI, and Unstable Angina). Remember, early recognition is key to effective management.

Review and Practice: Review previous lessons on ECG basics. Practice interpreting ECG strips with various ACS presentations. Focus on identifying ST-segment changes, T-wave abnormalities, and Q waves.

Next Day Preview: Tomorrow, we will focus on Bundle Branch Blocks, specifically Right Bundle Branch Block (RBBB) and Left Bundle Branch Block (LBBB). We will discuss the ECG criteria for each and their clinical significance.