CVT Electrocardiography (ECG/EKG) Techniques 3 — Questions and Answers
Question 1: A technician notices the QRS complexes alternate in amplitude on an ECG strip. This finding is called:
- Pulsus alternans
- Electrical alternans (Correct answer)
- Bigeminy
- Trigeminy
Correct answer: Electrical alternans
Electrical alternans is characterized by beat-to-beat variation in QRS amplitude and can indicate pericardial effusion or cardiac tamponade.
Question 2: Which electrode placement error causes the most clinically significant ECG distortion?
- V4 placed at V5 position
- Left arm and right arm leads reversed (Correct answer)
- V1 placed one space too high
- V6 placed slightly posterior
Correct answer: Left arm and right arm leads reversed
Reversing the left arm (LA) and right arm (RA) electrodes inverts lead I and swaps aVL and aVR, which can mimic dextrocardia or mask pathology.
Question 3: The QTc interval is calculated to correct for heart rate. Which formula is most commonly used?
- Fridericia formula
- Hodges formula
- Bazett formula (Correct answer)
- Framingham formula
Correct answer: Bazett formula
The Bazett formula (QTc = QT / √RR) is the most widely used method for heart rate correction of the QT interval despite its limitations at extreme rates.
Question 4: Posterior wall MI is best identified on a standard 12-lead ECG by which finding in leads V1–V2?
- ST elevation and Q waves
- Tall R waves and ST depression (Correct answer)
- Inverted T waves and wide QRS
- Prolonged PR interval
Correct answer: Tall R waves and ST depression
Posterior MI produces reciprocal changes in V1–V2: tall, broad R waves and ST depression representing the mirror image of posterior ST elevation and Q waves.
Question 5: To reduce 60-Hz AC interference on an ECG tracing, a technician should first:
- Increase paper speed to 50 mm/sec
- Check and re-prep electrode sites (Correct answer)
- Switch from 12-lead to 3-lead acquisition
- Reposition the patient to the right lateral decubitus
Correct answer: Check and re-prep electrode sites
Poor electrode-to-skin contact is the most common cause of AC interference; re-prepping the skin with abrasive prep and fresh gel usually eliminates it.
Question 6: In a complete left bundle branch block (LBBB), which finding is expected in lateral leads I, aVL, V5, and V6?
- RSR' pattern
- Broad, notched R waves (Correct answer)
- Deep S waves
- Prominent Q waves
Correct answer: Broad, notched R waves
LBBB produces broad, notched (M-shaped) R waves in lateral leads due to abnormal left ventricular depolarization.
Question 7: Which ECG change is associated with hypokalemia?
- Peaked T waves
- Shortened QT interval
- Prominent U waves (Correct answer)
- Widened P waves only
Correct answer: Prominent U waves
Hypokalemia classically produces prominent U waves (often larger than the T wave), flattened T waves, and a prolonged QU interval.
CVT Electrocardiography (ECG/EKG) Techniques 3
A technician notices the QRS complexes alternate in amplitude on an ECG strip.
This finding is called: