CCT Electrocardiography Procedures & Interpretation 5 — Questions and Answers
Question 1: Which of the following rhythms is defined by an atrial rate of 400–600 bpm with an irregularly irregular ventricular response?
- Atrial flutter
- Atrial fibrillation (Correct answer)
- Multifocal atrial tachycardia
- Ventricular fibrillation
Correct answer: Atrial fibrillation
Atrial fibrillation is characterized by chaotic atrial activity at 400–600 bpm with no distinct P waves and a completely irregular ventricular rate.
Question 2: In left bundle branch block (LBBB), which lead shows a broad monophasic R wave without a septal Q wave?
- Lead V1
- Lead aVR
- Lead V6 (Correct answer)
- Lead III
Correct answer: Lead V6
In LBBB, lead V6 (and lateral leads I, aVL) shows a broad, notched, monophasic R wave with absence of the normal septal Q wave.
Question 3: A CCT observes a patient's ECG with sudden onset of wide, bizarre QRS complexes at 180 bpm, with AV dissociation. What is the most likely rhythm?
- SVT with aberrant conduction
- Accelerated idioventricular rhythm
- Ventricular tachycardia (Correct answer)
- Torsades de pointes
Correct answer: Ventricular tachycardia
Ventricular tachycardia presents with wide, bizarre QRS complexes at ≥100 bpm and AV dissociation (independent P waves and QRS complexes) is a distinguishing feature.
Question 4: Which ECG finding is most consistent with acute pericarditis?
- ST elevation in a single coronary territory with reciprocal changes
- Diffuse concave (saddle-shaped) ST elevation in multiple leads with PR depression (Correct answer)
- New LBBB pattern
- Wellens' syndrome T-wave changes in V2-V3
Correct answer: Diffuse concave (saddle-shaped) ST elevation in multiple leads with PR depression
Acute pericarditis classically shows diffuse, concave (saddle-shaped) ST elevation in nearly all leads with PR segment depression, reflecting global pericardial inflammation.
Question 5: What electrode placement error causes the ECG to show inverted P waves and QRS complexes in lead I with a positive aVR?
- Left leg and right leg lead reversal
- Left arm and right arm lead reversal (Correct answer)
- V1 and V2 position swap
- Right arm and left leg reversal
Correct answer: Left arm and right arm lead reversal
Swapping the left arm (LA) and right arm (RA) electrodes causes lead I to be inverted and aVR to appear positive — the mirror image of normal.
Question 6: Which of the following best defines the J-point on the ECG?
- The peak of the R wave
- The junction between the end of the QRS complex and the beginning of the ST segment (Correct answer)
- The midpoint of the T wave
- The point where the PR segment meets the QRS complex
Correct answer: The junction between the end of the QRS complex and the beginning of the ST segment
The J-point marks the junction between the end of the QRS complex and the start of the ST segment, and is the reference for measuring ST elevation or depression.
Question 7: A patient on telemetry shows P waves that occur at a normal rate but none are followed by QRS complexes. What AV block is present?
- First-degree AV block
- Mobitz I second-degree AV block
- Mobitz II second-degree AV block
- Third-degree (complete) AV block (Correct answer)
Correct answer: Third-degree (complete) AV block
In complete (third-degree) AV block, no atrial impulses conduct to the ventricles; the atria and ventricles beat independently, so no P waves are followed by QRS complexes.
CCT Electrocardiography Procedures & Interpretation 5
Which of the following rhythms is defined by an atrial rate of 400–600 bpm with an irregularly irregular ventricular response?