Dysrhythmia ECG Monitoring & Analysis 1 — Questions and Answers
Question 1: What is the normal range for a PR interval on an ECG?
- 0.08 - 0.10 seconds
- 0.12 - 0.20 seconds (Correct answer)
- 0.22 - 0.30 seconds
- 0.30 - 0.40 seconds
Correct answer: 0.12 - 0.20 seconds
The PR interval represents the time it takes for an electrical impulse to travel from the sinoatrial (SA) node through the atria, AV node, and His-Purkinje system to the ventricles. A normal PR interval ranges from 0.12 to 0.20 seconds (3 to 5 small squares) on standard ECG paper. Deviations outside this range can indicate conduction abnormalities.
Question 2: Which ECG finding is characteristic of myocardial infarction?
- ST-segment elevation (Correct answer)
- Shortened PR interval
- Prolonged QT interval
- Flattened T waves
Correct answer: ST-segment elevation
ST-segment elevation on an ECG is a critical indicator of acute myocardial infarction (heart attack), specifically an ST-elevation myocardial infarction (STEMI). It signifies transmural ischemia, where the entire thickness of the heart muscle wall is deprived of oxygen due to a complete blockage of a coronary artery. This finding requires immediate medical intervention, such as reperfusion therapy.
Question 3: Which ECG lead placement provides a view of the heart’s electrical activity from the left lateral perspective?
- Lead II
- Lead III
- Lead aVL (Correct answer)
- Lead V1
Correct answer: Lead aVL
The 12-lead ECG provides different views of the heart's electrical activity. Lead aVL is one of the augmented unipolar limb leads and specifically offers a view of the heart from the high lateral wall, which is part of the left lateral perspective. This allows for detection of changes in this specific region of the myocardium.
Question 4: What does a prolonged QT interval indicate?
- Risk for bradycardia
- Risk for Torsades de Pointes (Correct answer)
- Risk for atrial fibrillation
- Improved cardiac output
Correct answer: Risk for Torsades de Pointes
A prolonged QT interval indicates a delay in ventricular repolarization, making the heart more vulnerable to developing dangerous arrhythmias. This increased vulnerability specifically predisposes individuals to Torsades de Pointes, a polymorphic ventricular tachycardia that can degenerate into ventricular fibrillation and sudden cardiac death. Therefore, identifying a prolonged QT interval is crucial for risk assessment.
Question 5: Which ECG abnormality suggests hyperkalemia?
- ST-segment depression
- Tall, peaked T waves (Correct answer)
- Shortened PR interval
- Prolonged QRS complex
Correct answer: Tall, peaked T waves
Hyperkalemia, an elevated potassium level in the blood, significantly affects cardiac electrical activity. One of the earliest and most characteristic ECG changes is the appearance of tall, narrow, and peaked T waves, often described as 'tented.' This reflects altered repolarization due to the increased extracellular potassium concentration.
Question 6: Which ECG change is commonly associated with hypokalemia?
- Elevated ST segment
- Peaked T waves
- Flattened or inverted T waves (Correct answer)
- Shortened QT interval
Correct answer: Flattened or inverted T waves
Hypokalemia, or low potassium levels, impacts myocardial repolarization. On an ECG, this often manifests as flattened T waves, which can progress to T wave inversion in more severe cases. Additionally, prominent U waves may appear, which are small waves following the T wave, further indicating potassium imbalance.
Dysrhythmia ECG Monitoring & Analysis 1
What is the normal range for a PR interval on an ECG?