ACLS Bradycardia 3 — Questions and Answers
Question 1: Which of the following ECG findings defines a second-degree AV block Mobitz type II?
- Progressively lengthening PR interval before a dropped beat
- Constant PR interval with sudden non-conducted P waves (Correct answer)
- No relationship between P waves and QRS complexes
- Shortened PR interval with delta waves
Correct answer: Constant PR interval with sudden non-conducted P waves
Mobitz type II is characterized by a constant PR interval with unexpected dropped QRS complexes.
Question 2: Why is Mobitz type II second-degree AV block considered more dangerous than Mobitz type I?
- It causes faster ventricular rates
- It frequently progresses to complete heart block (Correct answer)
- It is associated with atrial fibrillation
- It cannot be treated with pacing
Correct answer: It frequently progresses to complete heart block
Mobitz type II carries a high risk of sudden progression to complete (third-degree) AV block.
Question 3: A patient on beta-blockers develops symptomatic sinus bradycardia. After atropine fails, which infusion is a reasonable ACLS alternative to transcutaneous pacing?
- Epinephrine 2–10 mcg/min (Correct answer)
- Amiodarone 150 mg IV
- Adenosine 12 mg IV
- Magnesium sulfate 2 g IV
Correct answer: Epinephrine 2–10 mcg/min
Epinephrine infusion at 2–10 mcg/min is an ACLS-recommended vasopressor/chronotropic alternative when pacing is unavailable or atropine fails.
Question 4: On a rhythm strip, there is no consistent relationship between P waves and QRS complexes; P-P intervals are regular and R-R intervals are regular but different from each other. What is this rhythm?
- Second-degree AV block Mobitz I
- Second-degree AV block Mobitz II
- Third-degree (complete) AV block (Correct answer)
- Junctional tachycardia
Correct answer: Third-degree (complete) AV block
Complete (third-degree) AV block shows independent atrial and ventricular rhythms with no relationship between P waves and QRS complexes.
Question 5: Which of the following is a REVERSIBLE cause of bradycardia that the ACLS provider should search for using the 'H's and T's' framework?
- Hypokalemia
- Hyperkalemia (Correct answer)
- Hypertension
- Hypermagnesemia only applies to tachycardia
Correct answer: Hyperkalemia
Hyperkalemia can cause severe bradycardia and AV block and is a reversible H that must be identified and treated.
Question 6: A patient has a heart rate of 44 bpm with a BP of 80/50 mmHg. Atropine 1 mg IV is given with no improvement. Transcutaneous pacing is initiated but the patient remains hemodynamically unstable despite capture. What is the next step?
- Give a second dose of atropine 3 mg IV bolus
- Arrange transvenous pacing (Correct answer)
- Perform defibrillation
- Administer amiodarone 300 mg IV
Correct answer: Arrange transvenous pacing
Transvenous pacing provides more reliable and definitive pacing for patients who remain unstable despite transcutaneous pacing.
Question 7: Which medication used for acute coronary syndrome can cause symptomatic bradycardia and may need to be addressed in ACLS management?
- Aspirin
- Nitroglycerin
- Beta-blockers (Correct answer)
- Heparin
Correct answer: Beta-blockers
Beta-blockers reduce heart rate and AV conduction and can precipitate symptomatic bradycardia, particularly in patients with underlying conduction disease.
ACLS Bradycardia 3
Which of the following ECG findings defines a second-degree AV block Mobitz type II?