ECG ECG Lead Placement and Technique 1 — Questions and Answers
Question 1: What is the correct placement of the V1 precordial lead?
- Fourth intercostal space, right sternal border (Correct answer)
- Second intercostal space, right sternal border
- Fourth intercostal space, left sternal border
- Fifth intercostal space, midclavicular line
Correct answer: Fourth intercostal space, right sternal border
V1 is placed at the fourth intercostal space at the right sternal border. Correct lead placement is crucial for accurate ECG interpretation.
Question 2: What do limb leads I, II, and III measure?
- Electrical activity in the frontal plane from three different angles of Einthoven's triangle (Correct answer)
- Only heart rate
- Blood pressure changes
- Respiratory patterns
Correct answer: Electrical activity in the frontal plane from three different angles of Einthoven's triangle
Limb leads I, II, and III measure cardiac electrical activity in the frontal plane, forming Einthoven's triangle: Lead I (RA to LA), Lead II (RA to LL), Lead III (LA to LL).
Question 3: What artifact appears on an ECG when a patient is shivering?
- Baseline irregularity mimicking atrial fibrillation due to muscle tremor (Correct answer)
- Flat line (asystole)
- Perfectly regular sharp spikes
- Large wandering baseline
Correct answer: Baseline irregularity mimicking atrial fibrillation due to muscle tremor
Muscle tremor from shivering creates an irregular, jagged baseline that can mimic atrial fibrillation or obscure the underlying rhythm, requiring patient warming and stillness.
Question 4: What is a 12-lead ECG and why is it called that?
- A standard ECG recording using 10 electrodes that produce 12 different views of the heart's electrical activity (Correct answer)
- 12 separate ECG machines
- 12 electrodes placed on the chest
- An ECG taken over 12 minutes
Correct answer: A standard ECG recording using 10 electrodes that produce 12 different views of the heart's electrical activity
A 12-lead ECG uses 10 physical electrodes (4 limb, 6 precordial) to create 12 different electrical viewpoints of the heart, providing a comprehensive picture of cardiac electrical activity.
Question 5: What does a normal sinus rhythm look like on an ECG?
- Regular P waves before each QRS complex, consistent PR interval, rate 60-100 bpm, and upright P waves in lead II (Correct answer)
- No P waves visible
- Irregular R-R intervals
- QRS complexes wider than 120ms
Correct answer: Regular P waves before each QRS complex, consistent PR interval, rate 60-100 bpm, and upright P waves in lead II
Normal sinus rhythm shows regular rhythm with each P wave followed by a QRS complex, PR interval 0.12-0.20 seconds, QRS duration <0.12 seconds, and rate between 60-100 bpm.
Question 6: Why is proper skin preparation important before applying ECG electrodes?
- To reduce skin impedance and ensure good electrical contact for accurate signal recording (Correct answer)
- To prevent allergic reactions to electrode gel
- To sterilize the skin for surgery
- It has no practical effect on the recording
Correct answer: To reduce skin impedance and ensure good electrical contact for accurate signal recording
Cleaning the skin with alcohol, removing excess hair, and mildly abrading the surface reduces skin impedance, ensuring good electrode contact and minimizing artifact in the ECG recording.
ECG ECG Lead Placement and Technique 1
What is the correct placement of the V1 precordial lead?