ECG Electrocardiogram Knowledge Answers and Questions 3 — Questions and Answers
Question 1: 60-cycle (AC) interference on an ECG usually appears as:
- Uniform, thick, regular fine spikes across the tracing (Correct answer)
- A slow drifting baseline
- Random jagged deflections
- A completely flat line
Correct answer: Uniform, thick, regular fine spikes across the tracing
AC interference produces a consistent 60 Hz fuzzy pattern from nearby electrical sources.
Question 2: The SA node, the heart's natural pacemaker, is located in which chamber?
- Right atrium (Correct answer)
- Left atrium
- Right ventricle
- Left ventricle
Correct answer: Right atrium
The sinoatrial node sits in the upper wall of the right atrium.
Question 3: Which precordial lead is placed at the 5th intercostal space, midclavicular line?
- V4 (Correct answer)
- V1
- V2
- V6
Correct answer: V4
V4 is located at the 5th intercostal space along the midclavicular line.
Question 4: A wandering baseline artifact is most commonly caused by:
- Poor electrode contact or patient movement/respiration (Correct answer)
- Nearby AC power lines
- Muscle tremor
- Incorrect paper speed
Correct answer: Poor electrode contact or patient movement/respiration
Loose electrodes, lotion on skin, or breathing cause the baseline to drift.
Question 5: The PR interval measures the time from:
- Start of the P wave to the start of the QRS complex (Correct answer)
- Start of QRS to end of T wave
- Peak of R wave to next R wave
- End of T wave to next P wave
Correct answer: Start of the P wave to the start of the QRS complex
The PR interval reflects conduction from the atria through the AV node to the ventricles.
Question 6: Which limb lead views the heart from the left arm to the left leg?
- Lead III (Correct answer)
- Lead I
- Lead II
- aVR
Correct answer: Lead III
Lead III records the potential between the left arm and left leg.
Question 7: Before applying electrodes, the ECG technician should prepare the skin by:
- Cleaning and, if needed, lightly abrading and shaving the site (Correct answer)
- Applying a thick layer of lotion
- Wetting the site with saline only
- Leaving oils and hair in place
Correct answer: Cleaning and, if needed, lightly abrading and shaving the site
Clean, dry, hair-free skin ensures good electrode contact and a clear signal.
ECG Electrocardiogram Knowledge Answers and Questions 3
60-cycle (AC) interference on an ECG usually appears as: