ECC Cardiac Rhythm Recognition & Interpretation 2 — Questions and Answers
Question 1: Ventricular tachycardia (VT) is defined as which of the following?
- Three or more consecutive PVCs at a rate greater than 100 bpm (Correct answer)
- Atrial rate greater than ventricular rate with wide QRS
- Narrow-complex tachycardia with aberrant conduction
- P waves occurring after each wide QRS complex only
Correct answer: Three or more consecutive PVCs at a rate greater than 100 bpm
VT is defined as three or more consecutive ventricular complexes at a rate exceeding 100 bpm, originating below the bundle of His.
Question 2: Which ECG change is most specific for ST-elevation myocardial infarction (STEMI)?
- T-wave inversion in multiple leads
- ST-segment depression greater than 1 mm
- ST-segment elevation ≥1 mm in two or more contiguous leads (Correct answer)
- New right bundle branch block alone
Correct answer: ST-segment elevation ≥1 mm in two or more contiguous leads
STEMI is diagnosed when ST-segment elevation ≥1 mm is present in two or more contiguous leads, reflecting transmural myocardial injury in a shared coronary territory.
Question 3: In Mobitz Type II second-degree AV block, what is the hallmark ECG finding?
- Progressive PR prolongation before a dropped beat
- Sudden non-conducted P wave without prior PR interval changes (Correct answer)
- Complete AV dissociation with equal P and QRS rates
- P waves buried within QRS complexes
Correct answer: Sudden non-conducted P wave without prior PR interval changes
Mobitz Type II shows a sudden dropped QRS complex with no preceding PR prolongation, indicating an infranodal block that often progresses to complete heart block.
Question 4: Which cardiac arrest rhythm requires immediate defibrillation as primary treatment?
- Pulseless electrical activity (PEA)
- Asystole
- Ventricular fibrillation (Correct answer)
- Complete heart block with a pulse
Correct answer: Ventricular fibrillation
Ventricular fibrillation is a shockable rhythm where early defibrillation is the definitive treatment, as CPR alone cannot restore organized rhythm.
Question 5: Torsades de Pointes is most closely associated with which ECG abnormality?
- Short QT interval
- Prolonged QT interval (Correct answer)
- Delta waves indicating pre-excitation
- ST elevation in inferior leads
Correct answer: Prolonged QT interval
Torsades de Pointes is a form of polymorphic ventricular tachycardia that arises in the setting of a prolonged QT interval, which predisposes to early afterdepolarizations.
Question 6: What is the most common cause of a wide-complex tachycardia encountered in emergency settings?
- SVT with aberrant conduction
- Ventricular tachycardia (Correct answer)
- Hyperkalemia-induced intraventricular delay
- Pre-excitation (WPW) with antidromic conduction
Correct answer: Ventricular tachycardia
Ventricular tachycardia accounts for approximately 80% of all wide-complex tachycardias; it should be the presumptive diagnosis until proven otherwise.
Question 7: For a hemodynamically unstable patient with symptomatic sinus bradycardia, what is the correct first-line pharmacologic treatment per ACLS guidelines?
- Transcutaneous pacing immediately
- Atropine 0.5 mg IV (Correct answer)
- Dopamine infusion at 5 mcg/kg/min
- Adenosine 6 mg IV rapid push
Correct answer: Atropine 0.5 mg IV
Atropine 0.5 mg IV is the first-line drug for symptomatic bradycardia; transcutaneous pacing is the backup if atropine fails or is not available.
ECC Cardiac Rhythm Recognition & Interpretation 2
Ventricular tachycardia (VT) is defined as which of the following?