NHI Electrocardiography and Cardiac Monitoring 1 — Questions and Answers
Question 1: What does the P wave on an ECG represent?
- Ventricular depolarization
- Atrial depolarization (Correct answer)
- Ventricular repolarization
- Atrial repolarization
Correct answer: Atrial depolarization
The P wave reflects the electrical impulse that spreads through the atria causing atrial depolarization and contraction.
Question 2: The QRS complex on an ECG represents which cardiac event?
- Atrial depolarization
- Atrial repolarization
- Ventricular depolarization (Correct answer)
- Ventricular repolarization
Correct answer: Ventricular depolarization
The QRS complex reflects the rapid spread of the electrical impulse through the ventricles, causing ventricular depolarization and contraction.
Question 3: What is the normal range for heart rate in sinus rhythm?
- 40–60 bpm
- 60–100 bpm (Correct answer)
- 100–150 bpm
- 150–200 bpm
Correct answer: 60–100 bpm
Normal sinus rhythm is defined as a regular rhythm originating from the sinoatrial node with a rate between 60 and 100 beats per minute.
Question 4: How many electrodes are placed on a patient for a standard 12-lead ECG?
- 6
- 8
- 10 (Correct answer)
- 12
Correct answer: 10
A 12-lead ECG uses 10 electrodes—4 limb electrodes and 6 precordial (chest) electrodes—to produce 12 views of the heart's electrical activity.
Question 5: The T wave on an ECG represents which cardiac event?
- Atrial depolarization
- Ventricular depolarization
- Ventricular repolarization (Correct answer)
- Atrial repolarization
Correct answer: Ventricular repolarization
The T wave reflects ventricular repolarization—the recovery phase of the ventricles as they reset for the next contraction.
Question 6: Which is the correct placement for the V1 precordial lead?
- 4th intercostal space, left sternal border
- 4th intercostal space, right sternal border (Correct answer)
- 5th intercostal space, midaxillary line
- 2nd intercostal space, right sternal border
Correct answer: 4th intercostal space, right sternal border
V1 is placed at the 4th intercostal space along the right sternal border, making it the first chest lead closest to the right side of the heart.
Question 7: What is the standard paper speed used when recording an ECG?
- 10 mm/sec
- 25 mm/sec (Correct answer)
- 50 mm/sec
- 75 mm/sec
Correct answer: 25 mm/sec
The standard paper speed for ECG recording is 25 mm/sec, meaning each small square (1 mm) represents 0.04 seconds in time.
NHI Electrocardiography and Cardiac Monitoring 1
What does the P wave on an ECG represent?