Learning Objectives 🎯

• 💡 Define NSTEMI and Unstable Angina and differentiate between them.
• 📝 Identify key ECG changes associated with NSTEMI and Unstable Angina.
• 🔍 Understand the importance of clinical context in diagnosing these conditions.
• 📊 Discuss the role of cardiac biomarkers in the diagnosis.
• ✅ Recognize limitations of ECG interpretation in these scenarios.

Step-by-Step Content 📝

Introduction to Acute Coronary Syndromes (ACS) 🚑

ACS encompasses a range of conditions caused by reduced blood flow to the heart. We’ve already talked about STEMI, so now we will focus on the other two conditions that make up the triad: NSTEMI and Unstable Angina.

Unstable Angina 💔

Unstable angina is characterized by chest pain (angina) that is new, worsening, or occurs at rest. Critically, in unstable angina, there’s no evidence of myocardial necrosis (heart muscle death) based on cardiac biomarkers (like troponin). ECG changes may be present during episodes of pain, but often resolve. Think of it as a warning sign! ⚠️

• ECG Findings: ST-segment depression, T-wave inversion, or may be normal.
• Cardiac Biomarkers: Negative (troponin levels are not elevated).

NSTEMI (Non-ST-Segment Elevation Myocardial Infarction) ❤️‍🩹

NSTEMI involves myocardial necrosis (heart muscle damage), reflected in elevated cardiac biomarkers (troponin). ECG changes are similar to those seen in unstable angina, but the presence of elevated troponin is the defining difference. This means there’s actual damage to the heart muscle. 💔

• ECG Findings: ST-segment depression, T-wave inversion, or may be normal. (Same as Unstable Angina!)
• Cardiac Biomarkers: Positive (troponin levels are elevated).

Differentiating Between Unstable Angina and NSTEMI 🤔

The key distinction lies in the cardiac biomarkers. Remember, if troponin is elevated, it’s NSTEMI. If troponin is normal, it’s Unstable Angina. Clinical context is important, but the lab result is key. 🧪

ECG Changes in NSTEMI and Unstable Angina: A Closer Look 🔍

• ST-Segment Depression: Horizontal or downsloping ST-segment depression of ≥ 0.5 mm in two contiguous leads.
• T-Wave Inversion: Deep, symmetrical T-wave inversion in multiple leads.
• Transient ST-Segment Elevation: Sometimes, transient ST-segment elevation may be observed, but it is typically less pronounced than in STEMI.

Important Considerations 💡

• Normal ECG doesn’t rule out ACS: A normal ECG does NOT exclude the possibility of unstable angina or NSTEMI, especially if the patient is experiencing chest pain. Serial ECGs and cardiac biomarkers are crucial.
• Clinical Correlation: Always correlate ECG findings with the patient’s clinical presentation, risk factors, and history.

Quiz Time ❓

1. Which of the following is TRUE regarding unstable angina?
   A. Troponin levels are elevated.
   B. ST-segment elevation is always present.
   C. Troponin levels are normal. (Correct)
   D. Q waves are always present.
2. Which ECG finding is commonly associated with both NSTEMI and unstable angina?
   A. ST-segment elevation.
   B. ST-segment depression. (Correct)
   C. Q waves.
   D. Torsades de pointes.
3. What is the MOST important differentiating factor between unstable angina and NSTEMI?
   A. The severity of chest pain.
   B. The presence of ST-segment changes.
   C. Cardiac biomarker levels (troponin). (Correct)
   D. Patient’s age.
4. A patient presents with chest pain and ST-segment depression on their ECG. Initial troponin levels are normal. What is the MOST likely diagnosis?
   A. STEMI.
   B. NSTEMI.
   C. Unstable Angina. (Correct)
   D. Benign early repolarization.
5. A patient with a known history of coronary artery disease presents with worsening chest pain. Their ECG shows T-wave inversions in multiple leads. What is the NEXT BEST step in management?
   A. Administer aspirin and obtain serial troponin levels. (Correct)
   B. Immediately administer thrombolytics.
   C. Discharge the patient home.
   D. Perform a stress test.

Summary 📝

Today, we learned about NSTEMI and Unstable Angina, differentiating them by the presence or absence of elevated cardiac biomarkers. Remember, ECG changes can be subtle, and clinical context is essential for accurate diagnosis and management. Understanding these concepts is crucial for providing timely and effective care to patients with acute coronary syndromes. 👍

Review and Practice 📚

Review the ECG criteria for ST-segment depression and T-wave inversion. Practice interpreting ECG strips from patients with chest pain and compare them to clinical scenarios. Search online for sample ECGs of NSTEMI and Unstable Angina. 💻

Next Day Preview 🗓️

Tomorrow, we will move on to discuss bundle branch blocks and their implications. Get ready for more fascinating ECG patterns! 😉