ECG Basic Electrocardiogram 3 — Questions and Answers
Question 1: On standard ECG paper, how many seconds does one small (1 mm) box represent horizontally?
- 0.04 seconds (Correct answer)
- 0.20 seconds
- 0.10 seconds
- 0.01 seconds
Correct answer: 0.04 seconds
At the standard 25 mm/sec speed, each small horizontal box equals 0.04 seconds.
Question 2: Which limb electrode is considered the ground (neutral) and produces no tracing?
- Right leg (RL) (Correct answer)
- Left leg (LL)
- Right arm (RA)
- Left arm (LA)
Correct answer: Right leg (RL)
The right leg electrode serves as the ground/reference and does not generate a lead tracing.
Question 3: Which chest lead is placed at the fourth intercostal space to the right of the sternum?
- V1 (Correct answer)
- V6
- V4
- V2
Correct answer: V1
V1 is positioned at the fourth intercostal space just right of the sternal border.
Question 4: A wandering baseline artifact on an ECG is most often caused by:
- Patient movement or loose electrodes (Correct answer)
- AC electrical interference
- A fast heart rate
- A defective paper feed
Correct answer: Patient movement or loose electrodes
Baseline wander typically results from patient motion, respiration, or poorly attached electrodes.
Question 5: 60-cycle (AC) interference on an ECG appears as:
- A thick, fuzzy fine oscillation on the baseline (Correct answer)
- A slowly drifting baseline
- Random spikes with no pattern
- A completely flat line
Correct answer: A thick, fuzzy fine oscillation on the baseline
AC interference produces uniform fine, fuzzy oscillations from nearby electrical sources.
Question 6: Before applying chest electrodes, the technician should first:
- Prepare the skin by cleaning and, if needed, clipping hair (Correct answer)
- Apply electrodes over clothing
- Set the machine speed to 50 mm/sec
- Have the patient stand upright
Correct answer: Prepare the skin by cleaning and, if needed, clipping hair
Proper skin prep, including cleaning and hair removal, ensures good electrode contact and a clear tracing.
Question 7: The standard calibration mark on an ECG should produce a box that is:
- 10 mm tall (1 millivolt) (Correct answer)
- 5 mm tall
- 20 mm tall
- 2 mm tall
Correct answer: 10 mm tall (1 millivolt)
Standard calibration displays a 10 mm deflection representing 1 millivolt.
ECG Basic Electrocardiogram 3
On standard ECG paper, how many seconds does one small (1 mm) box represent horizontally?