CCT Electrocardiography Procedures & Interpretation 4 — Questions and Answers
Question 1: Which of the following correctly describes the placement of the V4 precordial electrode?
- 4th intercostal space, right sternal border
- 5th intercostal space, midclavicular line (Correct answer)
- 4th intercostal space, left sternal border
- 5th intercostal space, anterior axillary line
Correct answer: 5th intercostal space, midclavicular line
V4 is placed at the 5th intercostal space at the midclavicular line, serving as a transition point between septal and lateral precordial leads.
Question 2: An ECG shows a ventricular rate of 150 bpm with a sawtooth baseline pattern and 2:1 conduction. What rhythm is present?
- Atrial fibrillation
- Atrial flutter with 2:1 block (Correct answer)
- SVT with aberrant conduction
- Sinus tachycardia
Correct answer: Atrial flutter with 2:1 block
Atrial flutter typically produces a sawtooth (flutter wave) pattern at approximately 300 bpm atrial rate; with 2:1 conduction, the ventricular rate is ~150 bpm.
Question 3: Which ECG change is most associated with digitalis (digoxin) toxicity?
- ST segment elevation in multiple leads
- Bidirectional ventricular tachycardia (Correct answer)
- Tall peaked T waves
- Prolonged QT interval >600 ms
Correct answer: Bidirectional ventricular tachycardia
Bidirectional ventricular tachycardia, where the QRS axis alternates beat-to-beat, is a classic and serious sign of digitalis toxicity.
Question 4: What is the correct paper speed for a standard 12-lead ECG recording?
- 10 mm/sec
- 25 mm/sec (Correct answer)
- 50 mm/sec
- 100 mm/sec
Correct answer: 25 mm/sec
The standard ECG paper speed is 25 mm/sec, which allows accurate measurement of intervals and comparison across recordings.
Question 5: A right bundle branch block (RBBB) pattern on ECG is best identified by which finding?
- Wide QRS with rSR' (rabbit ear) pattern in V1 and wide S wave in lateral leads (Correct answer)
- Wide QRS with broad monophasic R wave in V5-V6
- ST elevation in V1-V3 with J-point notching
- Deep Q waves in leads I, aVL, V5-V6
Correct answer: Wide QRS with rSR' (rabbit ear) pattern in V1 and wide S wave in lateral leads
RBBB produces a wide QRS (≥0.12 s) with an rSR' or RSR' pattern (rabbit ears) in V1 and broad, slurred S waves in leads I, V5, and V6.
Question 6: Which condition can cause electrical alternans on the ECG?
- Pulmonary embolism
- Cardiac tamponade (Correct answer)
- Hypertrophic cardiomyopathy
- Acute pericarditis
Correct answer: Cardiac tamponade
Electrical alternans — beat-to-beat alternation in QRS amplitude — is a classic ECG sign of cardiac tamponade due to the heart swinging within a large pericardial effusion.
Question 7: When recording a 12-lead ECG, which action should the CCT take if baseline wander is observed?
- Increase the gain setting to 20 mm/mV
- Ask the patient to hold their breath and apply a low-frequency filter (Correct answer)
- Switch to a 50 mm/sec paper speed
- Move all electrodes two intercostal spaces superiorly
Correct answer: Ask the patient to hold their breath and apply a low-frequency filter
Baseline wander from respiratory movement can be reduced by asking the patient to hold their breath briefly and applying a low-frequency (baseline) filter.
CCT Electrocardiography Procedures & Interpretation 4
Which of the following correctly describes the placement of the V4 precordial electrode?