, Question 1
A telemetry strip shows a narrow-complex tachycardia at 180 bpm with no
visible P waves. The patient is hemodynamically stable. Which maneuver is
most likely to unmask the underlying rhythm and guide management?
A. Vagal stimulation via carotid sinus massage
B. Administration of intravenous adenosine 6 mg
C. Synchronized cardioversion at 100 J
D. Amiodarone 150 mg IV bolus
Correct Answer: B - Administration of intravenous adenosine 6
mg
RATIONALE
Adenosine transiently blocks the AV node, unmasking atrial activity
(e.g., flutter waves or ectopic P waves) and terminating AV nodal
reentrant tachycardia. Carotid massage is less reliable and carries risk;
cardioversion is for instability; amiodarone is not first-line for stable
narrow-complex tachycardia.
Question 2
A 12-lead ECG shows ST elevation in leads II, III, and aVF with reciprocal ST
depression in I and aVL. Which coronary artery is most likely occluded?
A. Left anterior descending artery
B. Left circumflex artery
C. Right coronary artery
D. Left main coronary artery
Correct Answer: C - Right coronary artery
RATIONALE
ST elevation in inferior leads (II, III, aVF) localizes to the inferior
wall, typically supplied by the right coronary artery (RCA) in a
right-dominant circulation. LAD causes anterior changes; circumflex
causes lateral changes; left main causes widespread changes.
Page 2
, Question 3
A patient with a dual-chamber pacemaker set to DDD mode at 60-120 bpm has
a programmed AV delay of 200 ms. The ECG shows pacing spikes before
every QRS but no preceding atrial spikes. What is the most likely explanation?
A. Atrial lead dislodgement
B. Pacemaker syndrome
C. Ventricular safety pacing
D. Atrial undersensing
Correct Answer: D - Atrial undersensing
RATIONALE
Atrial undersensing occurs when the pacemaker fails to detect intrinsic
atrial activity, leading to asynchronous atrial pacing (often with
spikes). Atrial lead dislodgement would cause failure to capture;
pacemaker syndrome is a clinical diagnosis; ventricular safety pacing
is a specific feature to avoid R-on-T.
Question 4
During ACLS, a patient in pulseless ventricular tachycardia has received one
shock and one dose of epinephrine. The rhythm remains unchanged. According
to current guidelines, which antiarrhythmic is indicated next?
A. Lidocaine 1-1.5 mg/kg IV push
B. Amiodarone 300 mg IV bolus
C. Magnesium sulfate 1-2 g IV
D. Sodium bicarbonate 1 mEq/kg IV
Correct Answer: B - Amiodarone 300 mg IV bolus
RATIONALE
Amiodarone 300 mg IV bolus is the preferred antiarrhythmic for
shock-refractory VF/pVT. Lidocaine is an alternative; magnesium is
for torsades; bicarbonate is not routinely recommended.
Page 3
A telemetry strip shows a narrow-complex tachycardia at 180 bpm with no
visible P waves. The patient is hemodynamically stable. Which maneuver is
most likely to unmask the underlying rhythm and guide management?
A. Vagal stimulation via carotid sinus massage
B. Administration of intravenous adenosine 6 mg
C. Synchronized cardioversion at 100 J
D. Amiodarone 150 mg IV bolus
Correct Answer: B - Administration of intravenous adenosine 6
mg
RATIONALE
Adenosine transiently blocks the AV node, unmasking atrial activity
(e.g., flutter waves or ectopic P waves) and terminating AV nodal
reentrant tachycardia. Carotid massage is less reliable and carries risk;
cardioversion is for instability; amiodarone is not first-line for stable
narrow-complex tachycardia.
Question 2
A 12-lead ECG shows ST elevation in leads II, III, and aVF with reciprocal ST
depression in I and aVL. Which coronary artery is most likely occluded?
A. Left anterior descending artery
B. Left circumflex artery
C. Right coronary artery
D. Left main coronary artery
Correct Answer: C - Right coronary artery
RATIONALE
ST elevation in inferior leads (II, III, aVF) localizes to the inferior
wall, typically supplied by the right coronary artery (RCA) in a
right-dominant circulation. LAD causes anterior changes; circumflex
causes lateral changes; left main causes widespread changes.
Page 2
, Question 3
A patient with a dual-chamber pacemaker set to DDD mode at 60-120 bpm has
a programmed AV delay of 200 ms. The ECG shows pacing spikes before
every QRS but no preceding atrial spikes. What is the most likely explanation?
A. Atrial lead dislodgement
B. Pacemaker syndrome
C. Ventricular safety pacing
D. Atrial undersensing
Correct Answer: D - Atrial undersensing
RATIONALE
Atrial undersensing occurs when the pacemaker fails to detect intrinsic
atrial activity, leading to asynchronous atrial pacing (often with
spikes). Atrial lead dislodgement would cause failure to capture;
pacemaker syndrome is a clinical diagnosis; ventricular safety pacing
is a specific feature to avoid R-on-T.
Question 4
During ACLS, a patient in pulseless ventricular tachycardia has received one
shock and one dose of epinephrine. The rhythm remains unchanged. According
to current guidelines, which antiarrhythmic is indicated next?
A. Lidocaine 1-1.5 mg/kg IV push
B. Amiodarone 300 mg IV bolus
C. Magnesium sulfate 1-2 g IV
D. Sodium bicarbonate 1 mEq/kg IV
Correct Answer: B - Amiodarone 300 mg IV bolus
RATIONALE
Amiodarone 300 mg IV bolus is the preferred antiarrhythmic for
shock-refractory VF/pVT. Lidocaine is an alternative; magnesium is
for torsades; bicarbonate is not routinely recommended.
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