Learning Objectives 🎯

• 💡 Understand the pathophysiology of how PE can affect the ECG.
• 📝 Identify the most common ECG findings associated with PE (e.g., S1Q3T3, sinus tachycardia).
• 📚 Recognize limitations of using ECG alone for PE diagnosis.
• 🔍 Differentiate PE ECG findings from other similar conditions.
• 💪 Interpret ECGs in the context of clinical scenarios suggestive of PE.

Step-by-Step Content 📝

Introduction to Pulmonary Embolism 🫁

Pulmonary Embolism (PE) occurs when a blood clot (usually from the legs) travels to the lungs and blocks a pulmonary artery. This obstruction can lead to reduced blood flow to the lungs, right ventricular strain, and potentially life-threatening complications.

ECG Changes in PE: Why They Happen 💔

PE can cause several ECG changes due to:

• Right Ventricular Strain: The sudden increase in pulmonary artery pressure puts a strain on the right ventricle (RV).
• Pulmonary Hypertension: The blockage increases pressure in the pulmonary circulation.
• Tachycardia: The body’s response to hypoxia (low oxygen) and stress.

Common ECG Findings in PE 🕵️‍♀️

Keep in mind that these findings are not always present, and PE can sometimes present with a normal ECG. However, be on the lookout for:

• Sinus Tachycardia: A heart rate greater than 100 bpm. This is the *most common* ECG finding in PE.
• S1Q3T3: A classic, but relatively infrequent, finding consisting of:
  • A prominent S wave in lead I.
  • A Q wave in lead III.
  • Inverted T wave in lead III.
• Right Axis Deviation: The QRS axis points to the right.
• Right Bundle Branch Block (RBBB): Can be new or pre-existing. A new RBBB is more suggestive of PE.
• T Wave Inversions: In the anterior leads (V1-V4), indicating right ventricular strain.
• Atrial Fibrillation/Flutter: PE can trigger atrial arrhythmias.

The Infamous S1Q3T3 Pattern Explained 🧐

The S1Q3T3 pattern arises from right ventricular dilation and pulmonary hypertension. While considered a classic sign, it’s only present in a small percentage of PE cases (estimated less than 20%). Don’t rely solely on this pattern to diagnose PE!

Important Caveats and Differential Diagnosis ⚠️

The ECG findings in PE are often nonspecific and can be seen in other conditions. It is crucial to consider other possible diagnoses, such as:

• Acute Myocardial Infarction (MI)
• Chronic Obstructive Pulmonary Disease (COPD)
• Pulmonary Hypertension (without PE)

Remember: The ECG should always be interpreted in the context of the patient’s clinical presentation and other diagnostic tests (e.g., CT angiography).

Clinical Scenario Example 🏥

A 65-year-old woman presents to the emergency department with sudden onset shortness of breath and chest pain. Her ECG shows sinus tachycardia and T wave inversions in V1-V3. While these findings are concerning for PE, further investigation (e.g., CT scan) is necessary to confirm the diagnosis.

Summary 📝

Pulmonary Embolism can cause various ECG changes, most commonly sinus tachycardia. Other findings include the S1Q3T3 pattern, right axis deviation, RBBB, and T wave inversions. However, these findings are nonspecific, and a normal ECG does not rule out PE. Always correlate ECG findings with the patient’s clinical presentation and other diagnostic tests.

Review and Practice 📚

Review the ECG criteria for right ventricular strain and right bundle branch block. Look at ECG strips online with confirmed PE diagnoses. Practice identifying potential PE-related changes.

Next Day Preview 🚀

Tomorrow, we’ll be learning about the ECG changes seen in various electrolyte imbalances (e.g., hyperkalemia, hypokalemia). Get ready to delve into the world of electrolytes and their impact on the heart!

Quiz Time ❓

1. Which of the following is the *most common* ECG finding in Pulmonary Embolism?
   A. S1Q3T3 pattern
   B. Atrial Fibrillation
   C. Sinus Tachycardia (Correct)
   D. Right Bundle Branch Block
2. The S1Q3T3 pattern consists of which of the following?
   A. S wave in lead I, Q wave in lead III, upright T wave in lead III
   B. Q wave in lead I, S wave in lead III, inverted T wave in lead III
   C. S wave in lead I, Q wave in lead III, inverted T wave in lead III (Correct)
   D. Q wave in lead I, S wave in lead III, upright T wave in lead III
3. A new Right Bundle Branch Block (RBBB) in the setting of acute shortness of breath should raise suspicion for:
   A. Left Ventricular Hypertrophy
   B. Pulmonary Embolism (Correct)
   C. Myocardial Infarction in the Left Anterior Descending Artery territory
   D. Hyperkalemia
4. Which of the following ECG changes is most specific for Pulmonary Embolism?
   A. Sinus Tachycardia
   B. S1Q3T3 pattern (Correct)
   C. T wave inversions in V1-V4
   D. Right Axis Deviation
5. A patient presents with chest pain and dyspnea. Their ECG shows T wave inversions in leads V1-V4. What is the most appropriate next step?
   A. Immediately administer aspirin.
   B. Order a CT Angiogram to rule out Pulmonary Embolism (Correct)
   C. Start the patient on antibiotics.
   D. Reassure the patient that their ECG is normal.