NHI Electrocardiography and Cardiac Monitoring 2 — Questions and Answers
Question 1: Where should the RA (right arm) electrode be placed for a 12-lead ECG?
- On the right leg below the knee
- On the left arm above the wrist
- On the right arm above the wrist (Correct answer)
- On the left leg below the knee
Correct answer: On the right arm above the wrist
The RA electrode is placed on the right arm, typically above the wrist, to record the electrical potential from the right upper extremity.
Question 2: Which electrode serves as the electrical ground in a standard 12-lead ECG?
- LA (left arm)
- RA (right arm)
- RL (right leg) (Correct answer)
- LL (left leg)
Correct answer: RL (right leg)
The RL (right leg) electrode is the ground electrode; it reduces electrical interference and is not used to form any of the 12 leads.
Question 3: Somatic tremor artifact on an ECG is most commonly caused by:
- Electrical interference from nearby equipment
- Involuntary patient movement or muscle activity (Correct answer)
- Loose electrode connections
- Incorrect paper speed setting
Correct answer: Involuntary patient movement or muscle activity
Somatic tremor artifact results from voluntary or involuntary patient muscle movement, causing irregular baseline disturbances on the ECG tracing.
Question 4: The normal PR interval duration on an ECG is:
- 0.04–0.10 seconds
- 0.06–0.10 seconds
- 0.12–0.20 seconds (Correct answer)
- 0.20–0.30 seconds
Correct answer: 0.12–0.20 seconds
The normal PR interval is 0.12 to 0.20 seconds, representing conduction time from the atria through the AV node to the ventricles.
Question 5: Which precordial lead is placed at the 5th intercostal space, left midclavicular line?
- V3
- V4 (Correct answer)
- V5
- V6
Correct answer: V4
V4 is placed at the 5th intercostal space at the left midclavicular line, an important landmark for accurate precordial lead positioning.
Question 6: AC interference (60-cycle artifact) on an ECG appears as:
- Wandering baseline with slow undulations
- An irregularly irregular cardiac rhythm
- A fuzzy, thickened baseline with 60 tiny spikes per second (Correct answer)
- Absent P waves with wide QRS complexes
Correct answer: A fuzzy, thickened baseline with 60 tiny spikes per second
AC interference from nearby electrical equipment appears as a regularly fuzzy or thickened baseline caused by 60-cycle per second electrical noise.
Question 7: The QT interval on an ECG represents:
- Time for atrial depolarization only
- Total ventricular electrical activity including both depolarization and repolarization (Correct answer)
- Time between two consecutive heartbeats
- The PR interval added to the QRS duration
Correct answer: Total ventricular electrical activity including both depolarization and repolarization
The QT interval spans from the start of the QRS complex to the end of the T wave, encompassing total ventricular depolarization and repolarization.
NHI Electrocardiography and Cardiac Monitoring 2
Where should the RA (right arm) electrode be placed for a 12-lead ECG?