ACSM-EP Electrocardiography 3 — Questions and Answers
Question 1: Which ECG finding is characteristic of left bundle branch block (LBBB)?
- rSR' pattern in V1 and wide S wave in V6
- Wide QRS (≥0.12 s) with broad monophasic R wave in V5–V6 and deep S in V1 (Correct answer)
- Short PR interval with delta wave
- Peaked P waves in leads II and V1
Correct answer: Wide QRS (≥0.12 s) with broad monophasic R wave in V5–V6 and deep S in V1
LBBB shows a broad, notched R wave in lateral leads (I, aVL, V5–V6) and a deep QS or rS in V1, with QRS duration ≥0.12 seconds.
Question 2: A 45-year-old athlete's resting ECG shows sinus bradycardia at 48 bpm with no symptoms. What is the most appropriate action?
- Refer immediately for pacemaker evaluation
- Administer atropine
- Consider it a normal training adaptation and document it (Correct answer)
- Terminate all exercise training
Correct answer: Consider it a normal training adaptation and document it
Sinus bradycardia in well-trained athletes is a common physiologic adaptation due to increased vagal tone and does not require intervention if asymptomatic.
Question 3: What ECG change is associated with hyperkalemia?
- Prolonged QT interval and U waves
- Peaked (tall, narrow) T waves followed by widening QRS (Correct answer)
- Short PR interval with delta waves
- ST-segment depression in lateral leads
Correct answer: Peaked (tall, narrow) T waves followed by widening QRS
Hyperkalemia classically produces tall peaked T waves early, followed by PR prolongation, QRS widening, and eventually a sine-wave pattern as potassium rises.
Question 4: During an exercise test, the exercise physiologist observes three consecutive wide-complex beats at >100 bpm. This finding is best described as:
- Supraventricular tachycardia with aberrancy
- Non-sustained ventricular tachycardia (Correct answer)
- Accelerated idioventricular rhythm
- Bundle branch block
Correct answer: Non-sustained ventricular tachycardia
Three or more consecutive wide-complex beats at a rate >100 bpm lasting <30 seconds defines non-sustained ventricular tachycardia.
Question 5: Which ECG lead is placed at the fourth intercostal space, right sternal border?
- V1 (Correct answer)
- V2
- V3
- V4
Correct answer: V1
V1 is positioned at the fourth intercostal space to the right of the sternum, directly opposite V2 on the left sternal border.
Question 6: A delta wave on an ECG is pathognomonic of which condition?
- Brugada syndrome
- Wolff-Parkinson-White (WPW) syndrome (Correct answer)
- Long QT syndrome
- Hypertrophic cardiomyopathy
Correct answer: Wolff-Parkinson-White (WPW) syndrome
A delta wave (slurred upstroke of the QRS) results from ventricular pre-excitation via an accessory pathway, which is the hallmark of WPW syndrome.
Question 7: In ECG interpretation, what does the term 'axis deviation' refer to?
- Abnormal heart rate
- The mean direction of ventricular depolarization in the frontal plane (Correct answer)
- Displacement of the heart within the chest
- Abnormal P-wave morphology
Correct answer: The mean direction of ventricular depolarization in the frontal plane
Cardiac axis describes the mean vector of ventricular depolarization; left axis deviation (<-30°) and right axis deviation (>+100°) can indicate specific pathological conditions.
ACSM-EP Electrocardiography 3
Which ECG finding is characteristic of left bundle branch block (LBBB)?