CCT Electrocardiography Procedures & Interpretation 3 — Questions and Answers
Question 1: Which ECG pattern is associated with hyperkalemia?
- Prolonged PR and U waves
- Tall peaked T waves progressing to widened QRS (Correct answer)
- ST depression in lateral leads
- Short QT interval with delta waves
Correct answer: Tall peaked T waves progressing to widened QRS
Hyperkalemia first produces tall, narrow, peaked T waves; as potassium rises further, the PR prolongs, QRS widens, and ultimately a sine-wave pattern may develop.
Question 2: On a standard ECG tracing run at 25 mm/sec, how long does each large box (5 mm) represent in time?
- 0.04 seconds
- 0.10 seconds
- 0.20 seconds (Correct answer)
- 0.40 seconds
Correct answer: 0.20 seconds
At the standard paper speed of 25 mm/sec, each large box (5 mm wide) represents 0.20 seconds (200 ms).
Question 3: A patient's ECG shows P waves that change morphology beat to beat with a rate of 105 bpm. What is this rhythm?
- Multifocal atrial tachycardia (Correct answer)
- Atrial flutter with variable block
- Wandering atrial pacemaker
- Atrial fibrillation
Correct answer: Multifocal atrial tachycardia
Multifocal atrial tachycardia (MAT) features at least three distinct P-wave morphologies, irregular rhythm, and a rate >100 bpm, often seen in COPD patients.
Question 4: Which ECG lead is most commonly used as the monitoring lead in continuous cardiac monitoring?
- Lead I
- Lead II (Correct answer)
- Lead aVL
- Lead V4
Correct answer: Lead II
Lead II is the standard monitoring lead because it provides the best view of P waves and QRS complexes for rhythm assessment.
Question 5: ST depression in leads V1–V4 during an acute coronary event should raise concern for which condition?
- Anterior STEMI
- Posterior MI (reciprocal changes) (Correct answer)
- Pericarditis
- Left ventricular hypertrophy
Correct answer: Posterior MI (reciprocal changes)
ST depression in V1–V4 can represent reciprocal changes of a true posterior MI, which would show ST elevation in posterior leads V7–V9.
Question 6: What is the normal axis range for QRS complex in an adult ECG?
- -90° to -30°
- -30° to +90° (Correct answer)
- +90° to +180°
- 0° to +180°
Correct answer: -30° to +90°
The normal QRS axis in adults ranges from -30° to +90°, reflecting the predominant leftward and inferior direction of ventricular depolarization.
Question 7: A CCT notices the ECG shows a regularly irregular rhythm where the PR interval progressively lengthens until a QRS is dropped. What is this rhythm?
- First-degree AV block
- Mobitz I (Wenckebach) second-degree AV block (Correct answer)
- Mobitz II second-degree AV block
- Complete (third-degree) AV block
Correct answer: Mobitz I (Wenckebach) second-degree AV block
Mobitz I (Wenckebach) is characterized by progressive PR prolongation until a P wave fails to conduct and the QRS is dropped, then the cycle repeats.
CCT Electrocardiography Procedures & Interpretation 3
Which ECG pattern is associated with hyperkalemia?