Free NCMA EKG/ECG Lead Placement and Artifacts Questions and Answers 1 — Questions and Answers
Question 1: Where is the V4 precordial electrode placed for a standard 12-lead EKG?
- Fourth intercostal space, right sternal border
- Fifth intercostal space, left midclavicular line (Correct answer)
- Fifth intercostal space, anterior axillary line
- Fourth intercostal space, left sternal border
Correct answer: Fifth intercostal space, left midclavicular line
Proper lead placement is critical for an accurate EKG. The V4 electrode is placed in the fifth intercostal space at the midclavicular line. This placement follows the placement of V1, V2, and V3, and provides a specific view of the heart's electrical activity.
Question 2: An EKG tracing shows a fuzzy, irregular baseline with erratic spikes. This is most likely caused by which type of artifact?
- AC Interference
- Wandering Baseline
- Somatic Tremor (Correct answer)
- Interrupted Baseline
Correct answer: Somatic Tremor
Somatic tremor is an artifact caused by muscle movement, such as patient shivering, talking, or involuntary tremors. It appears as a fuzzy, erratic baseline on the EKG tracing. Ensuring the patient is warm, comfortable, and still can help minimize this type of artifact.
Question 3: On an EKG, what does the P wave represent?
- Ventricular depolarization
- Ventricular repolarization
- Atrial depolarization (Correct answer)
- Atrial repolarization
Correct answer: Atrial depolarization
The P wave is the first positive deflection on the EKG and represents atrial depolarization. This is the electrical activation of the atria, which leads to atrial contraction. The QRS complex represents ventricular depolarization, and the T wave represents ventricular repolarization.
Question 4: A wandering baseline artifact on an EKG is often caused by:
- Patient shivering
- Improper grounding of the EKG machine
- Poor electrode contact or patient breathing (Correct answer)
- Nearby electrical equipment
Correct answer: Poor electrode contact or patient breathing
A wandering baseline is a slow, undulating up-and-down motion of the entire tracing. It is often caused by poor electrode contact with the skin, which can be due to lotions, oils, sweat, or patient movement like deep breathing. Properly preparing the skin and ensuring electrodes are secure can prevent this artifact.
Question 5: Which limb electrode is considered the ground lead in a standard 12-lead EKG?
- Right Arm (RA)
- Left Arm (LA)
- Left Leg (LL)
- Right Leg (RL) (Correct answer)
Correct answer: Right Leg (RL)
The right leg (RL) electrode serves as the ground lead in an EKG. Its purpose is to minimize electrical interference from outside sources, which helps to produce a clearer tracing. While it is placed on the patient, it does not contribute to any of the specific EKG leads but is essential for the overall quality of the recording.
Question 6: AC interference on an EKG tracing appears as:
- A slow, wandering up-and-down line
- A series of small, uniform spikes creating a thick, fuzzy line (Correct answer)
- A flat line where the tracing should be
- Large, erratic spikes caused by muscle movement
Correct answer: A series of small, uniform spikes creating a thick, fuzzy line
AC (alternating current) interference is caused by electrical interference from nearby power sources, such as lights, power cords, and other medical equipment. It appears as a uniform, thick, and shaky line, typically with small, rapid spikes at a frequency of 60 Hz in the United States. Ensuring the patient bed is away from walls and unplugging non-essential equipment can resolve this.
Free NCMA EKG/ECG Lead Placement and Artifacts Questions and Answers 1
Where is the V4 precordial electrode placed for a standard 12-lead EKG?