NRCMA EKG Basics 3 — Questions and Answers
Question 1: On EKG graph paper running at standard speed (25 mm/sec), one large box represents how many seconds?
- 0.20 seconds (Correct answer)
- 0.04 seconds
- 0.10 seconds
- 0.50 seconds
Correct answer: 0.20 seconds
Each large box on standard EKG paper equals 0.20 seconds (5 small boxes × 0.04 seconds each).
Question 2: Sinus tachycardia is defined as a heart rate above:
- 100 bpm (Correct answer)
- 90 bpm
- 120 bpm
- 80 bpm
Correct answer: 100 bpm
Sinus tachycardia is defined as a regular rhythm originating from the sinus node with a rate exceeding 100 bpm.
Question 3: Which EKG change is a hallmark of an acute ST-elevation myocardial infarction (STEMI)?
- ST segment elevation ≥1 mm in two contiguous leads (Correct answer)
- PR interval prolongation
- Peaked P waves
- Widened QRS complex only
Correct answer: ST segment elevation ≥1 mm in two contiguous leads
STEMI is diagnosed when ST elevation ≥1 mm appears in two or more anatomically contiguous leads.
Question 4: What does the term 'axis deviation' refer to on an EKG?
- The overall direction of ventricular depolarization in the frontal plane (Correct answer)
- The speed of conduction through the bundle of His
- The amplitude of the R wave
- The duration of atrial contraction
Correct answer: The overall direction of ventricular depolarization in the frontal plane
Axis deviation describes whether the mean electrical vector of ventricular depolarization is shifted left or right from normal.
Question 5: A medical assistant notices a saw-tooth pattern between QRS complexes at a rate of 300 bpm. This is characteristic of:
- Atrial flutter (Correct answer)
- Atrial fibrillation
- Ventricular fibrillation
- Supraventricular tachycardia
Correct answer: Atrial flutter
Atrial flutter produces a distinctive saw-tooth (flutter wave) pattern at approximately 300 atrial beats per minute.
Question 6: Right bundle branch block (RBBB) on EKG is characterized by a QRS duration of at least:
- 0.12 seconds (Correct answer)
- 0.08 seconds
- 0.10 seconds
- 0.16 seconds
Correct answer: 0.12 seconds
RBBB produces a wide QRS complex of 0.12 seconds or greater with an RSR' (rabbit ear) pattern in V1.
Question 7: Which electrode placement is correct for lead V4?
- 5th intercostal space at the midclavicular line (Correct answer)
- 4th intercostal space right sternal border
- 5th intercostal space at anterior axillary line
- 4th intercostal space left sternal border
Correct answer: 5th intercostal space at the midclavicular line
V4 is placed at the 5th intercostal space at the midclavicular line on the left side.
NRCMA EKG Basics 3
On EKG graph paper running at standard speed (25 mm/sec), one large box represents how many seconds?