CCT Electrocardiography Procedures & Interpretation 2 — Questions and Answers
Question 1: Which ECG finding is most characteristic of Wolff-Parkinson-White (WPW) syndrome?
- Prolonged QT interval
- Delta wave with short PR interval (Correct answer)
- Tall peaked P waves
- Widened QRS with RBBB morphology only
Correct answer: Delta wave with short PR interval
WPW syndrome is characterized by a delta wave (slurred upstroke of the QRS) and a short PR interval due to an accessory pathway bypassing the AV node.
Question 2: A patient's ECG shows ST elevation in leads II, III, and aVF. Which coronary artery is most likely occluded?
- Left anterior descending artery
- Left circumflex artery
- Right coronary artery (Correct answer)
- Left main coronary artery
Correct answer: Right coronary artery
ST elevation in leads II, III, and aVF indicates an inferior STEMI, most commonly caused by occlusion of the right coronary artery.
Question 3: What does a QTc interval greater than 500 ms indicate?
- Benign early repolarization
- Significantly increased risk of torsades de pointes (Correct answer)
- Normal variant in females
- Evidence of right ventricular hypertrophy
Correct answer: Significantly increased risk of torsades de pointes
A QTc >500 ms represents a clinically significant prolongation that markedly increases the risk of the potentially fatal arrhythmia torsades de pointes.
Question 4: Which artifact on an ECG is most commonly caused by patient movement or muscle tremor?
- Baseline wander
- AC interference (60-Hz noise)
- Somatic muscle artifact (Correct answer)
- Electrode pop artifact
Correct answer: Somatic muscle artifact
Somatic muscle artifact produces irregular, high-frequency deflections on the ECG tracing and results from involuntary or voluntary skeletal muscle activity.
Question 5: In a 12-lead ECG, which lead is considered the best for identifying P-wave morphology?
- Lead I
- Lead aVR
- Lead II (Correct answer)
- Lead V1
Correct answer: Lead II
Lead II is oriented closely along the axis of normal atrial depolarization, making P waves most prominent and upright, which is ideal for rhythm analysis.
Question 6: A CCT records an ECG showing a heart rate of 40 bpm with narrow QRS complexes and no identifiable P waves. What rhythm is most likely?
- Junctional escape rhythm (Correct answer)
- Idioventricular rhythm
- Sinus bradycardia
- Second-degree AV block Mobitz I
Correct answer: Junctional escape rhythm
A junctional escape rhythm typically produces a rate of 40–60 bpm with narrow QRS complexes and absent, retrograde, or buried P waves.
Question 7: What is the primary purpose of applying conductive gel or electrode paste during ECG electrode placement?
- To prevent skin burns from electrical current
- To reduce skin-electrode impedance and improve signal quality (Correct answer)
- To mark electrode placement sites for future reference
- To cool the skin and reduce patient discomfort
Correct answer: To reduce skin-electrode impedance and improve signal quality
Conductive gel lowers the electrical impedance between the skin and the electrode, ensuring a clean, low-noise ECG signal.
CCT Electrocardiography Procedures & Interpretation 2
Which ECG finding is most characteristic of Wolff-Parkinson-White (WPW) syndrome?