ACSM-EP Electrocardiography 4 — Questions and Answers
Question 1: Which of the following correctly describes first-degree AV block?
- Progressively lengthening PR until a beat is dropped
- PR interval >0.20 seconds with all P waves conducted (Correct answer)
- Complete dissociation of P waves and QRS complexes
- Occasional non-conducted P waves with constant PR interval
Correct answer: PR interval >0.20 seconds with all P waves conducted
First-degree AV block is defined by a PR interval consistently greater than 0.20 seconds (one large square), with every P wave followed by a QRS complex.
Question 2: What ECG pattern is associated with right ventricular strain during exercise?
- ST elevation in V5–V6
- S1Q3T3 pattern with ST changes in right precordial leads (Correct answer)
- Deep Q waves in inferior leads
- Prolonged QT with U waves
Correct answer: S1Q3T3 pattern with ST changes in right precordial leads
Right ventricular strain classically produces an S wave in lead I, Q wave in lead III, and T-wave inversion in lead III (S1Q3T3), often with right precordial ST changes.
Question 3: During exercise testing, at what point past the J-point should ST-segment displacement be measured?
- 20 ms (0.5 small squares)
- 40 ms (1 small square)
- 60 ms (1.5 small squares)
- 80 ms (2 small squares) (Correct answer)
Correct answer: 80 ms (2 small squares)
The standard for measuring exercise-induced ST depression is 80 ms (2 small squares) after the J-point to allow the ST segment to stabilize after the QRS complex.
Question 4: A patient taking digoxin shows which characteristic ECG finding?
- Peaked T waves with tall P waves
- Scooped (reversed tick) ST-segment depression (Correct answer)
- Delta waves with short PR interval
- Wide QRS with RBBB pattern
Correct answer: Scooped (reversed tick) ST-segment depression
Digoxin produces a characteristic 'scooped' or reversed-tick ST-segment depression, especially in lateral leads, which is a normal therapeutic finding distinct from ischemia.
Question 5: Which finding on a resting ECG would be an absolute contraindication to initiating an exercise stress test?
- Sinus bradycardia at 55 bpm
- Uncontrolled ventricular tachycardia (Correct answer)
- First-degree AV block
- Isolated premature atrial contractions
Correct answer: Uncontrolled ventricular tachycardia
Uncontrolled ventricular tachycardia is an absolute contraindication to exercise testing because exercise could precipitate ventricular fibrillation.
Question 6: The Bazett formula is used to calculate which ECG measurement?
- Corrected QT interval (QTc) (Correct answer)
- Heart rate from R-R interval
- ST-segment slope
- P-wave axis
Correct answer: Corrected QT interval (QTc)
The Bazett formula (QTc = QT / √RR) corrects the QT interval for heart rate, allowing comparison across different heart rates.
Question 7: In a 12-lead ECG, which leads are considered the lateral leads?
- II, III, aVF
- V1, V2, V3
- I, aVL, V5, V6 (Correct answer)
- aVR, aVL, aVF
Correct answer: I, aVL, V5, V6
The lateral leads (I, aVL, V5, V6) face the lateral wall of the left ventricle and are used to detect lateral wall ischemia or LVH voltage criteria.
ACSM-EP Electrocardiography 4
Which of the following correctly describes first-degree AV block?