CCI ECG Rhythm Interpretation 5 — Questions and Answers
Question 1: Which ECG pattern is associated with Brugada syndrome?
- Coved ST elevation in V1–V2 with RBBB morphology (Correct answer)
- Diffuse ST elevation with PR depression
- ST depression in V4–V6 with tall R waves
- Prolonged QT with prominent U waves
Correct answer: Coved ST elevation in V1–V2 with RBBB morphology
Brugada syndrome shows a characteristic coved-type ST elevation (≥2 mm) with RBBB morphology in leads V1–V2, linked to risk of sudden cardiac death.
Question 2: What is the corrected QT interval (QTc) formula using Bazett's correction?
- QT divided by the square root of the RR interval (in seconds) (Correct answer)
- QT multiplied by the heart rate divided by 60
- QT plus 0.04 × heart rate
- QT divided by the RR interval
Correct answer: QT divided by the square root of the RR interval (in seconds)
Bazett's formula corrects the QT interval for heart rate: QTc = QT / √RR, where RR is measured in seconds.
Question 3: A patient's rhythm strip shows grouped beating with progressively lengthening PR intervals until a P wave fails to conduct. What is the rhythm?
- Second-degree AV block, Mobitz type I (Wenckebach) (Correct answer)
- Second-degree AV block, Mobitz type II
- Third-degree AV block
- First-degree AV block with PACs
Correct answer: Second-degree AV block, Mobitz type I (Wenckebach)
Wenckebach (Mobitz I) is defined by progressive PR prolongation followed by a non-conducted P wave, then the cycle repeats.
Question 4: In left bundle branch block (LBBB), which leads typically show broad monophasic R waves?
- I, aVL, V5, V6 (Correct answer)
- V1, V2, V3
- II, III, aVF
- aVR, V1, V4
Correct answer: I, aVL, V5, V6
LBBB produces broad, notched, or slurred monophasic R waves in the lateral leads (I, aVL, V5, V6) due to delayed left ventricular depolarization.
Question 5: A post-cardiac surgery patient's ECG shows alternating electrical axis with every other beat. What is this finding called?
- Electrical alternans (Correct answer)
- Bidirectional ventricular tachycardia
- Bigeminy
- Intermittent bundle branch block
Correct answer: Electrical alternans
Electrical alternans is the beat-to-beat alternation in QRS amplitude or axis, classically associated with pericardial effusion and cardiac tamponade.
Question 6: Which supraventricular tachycardia produces a 'pseudo-R prime' in V1 and 'pseudo-S' in inferior leads during tachycardia?
- AV nodal reentrant tachycardia (AVNRT) (Correct answer)
- Atrial tachycardia
- AV reentrant tachycardia (AVRT) using a left-sided pathway
- Sinus tachycardia
Correct answer: AV nodal reentrant tachycardia (AVNRT)
Typical AVNRT has retrograde P waves buried in or just after the QRS, producing pseudo-R' in V1 and pseudo-S in II, III, aVF.
Question 7: What is the most reliable criterion to diagnose ventricular tachycardia vs. SVT with aberrancy using the Brugada algorithm?
- Absence of RS complex in all precordial leads (Correct answer)
- QRS duration >0.14 seconds
- AV dissociation on rhythm strip
- Axis deviation beyond –90 degrees
Correct answer: Absence of RS complex in all precordial leads
The first step of the Brugada algorithm is to check for the absence of any RS complex in all precordial leads; if present, VT is diagnosed immediately.
CCI ECG Rhythm Interpretation 5
Which ECG pattern is associated with Brugada syndrome?