Beat Reading Heart Beat Reading 3 — Questions and Answers
Question 1: Which of the following is the correct sequence of normal cardiac electrical conduction?
- SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers (Correct answer)
- AV node → SA node → Bundle of His → Purkinje fibers → Bundle branches
- SA node → Bundle of His → AV node → Bundle branches → Purkinje fibers
- AV node → Bundle branches → Bundle of His → SA node → Purkinje fibers
Correct answer: SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers
Normal conduction travels from the SA node to the AV node, then through the Bundle of His, bundle branches, and finally the Purkinje fibers.
Question 2: Saw-tooth flutter waves at approximately 300 bpm with regular ventricular response of 75 bpm suggests:
- Atrial fibrillation with controlled rate
- Atrial flutter with 4:1 conduction (Correct answer)
- Supraventricular tachycardia
- Ventricular tachycardia
Correct answer: Atrial flutter with 4:1 conduction
Classic atrial flutter has atrial rates around 300 bpm; a ventricular rate of 75 bpm reflects 4:1 AV conduction ratio.
Question 3: A patient develops sudden wide-complex tachycardia at 180 bpm after an MI. The MOST dangerous rhythm to rule out is:
- Supraventricular tachycardia with aberrancy
- Accelerated idioventricular rhythm
- Ventricular tachycardia (Correct answer)
- Junctional tachycardia
Correct answer: Ventricular tachycardia
Ventricular tachycardia is life-threatening and must be ruled out first when wide-complex tachycardia occurs post-MI.
Question 4: On an ECG, the isoelectric line between the S wave and T wave is called the:
- PR segment
- ST segment (Correct answer)
- QT interval
- TP segment
Correct answer: ST segment
The ST segment is the flat section between the end of the S wave and the beginning of the T wave, and its elevation or depression indicates ischemia or injury.
Question 5: Which lead is considered the best single lead for detecting P waves?
- Lead I
- Lead II (Correct answer)
- Lead aVL
- Lead V1
Correct answer: Lead II
Lead II is typically the best lead for visualizing P waves because electrical activity flows toward its positive electrode in normal sinus rhythm.
Question 6: Premature ventricular contractions (PVCs) are identified on ECG by:
- Narrow QRS with abnormal P wave
- Wide, bizarre QRS with no preceding P wave and compensatory pause (Correct answer)
- Prolonged PR interval with normal QRS
- P wave buried in QRS complex
Correct answer: Wide, bizarre QRS with no preceding P wave and compensatory pause
PVCs arise from ventricular ectopic foci, producing wide (>0.12 sec) bizarre QRS complexes not preceded by a P wave, usually followed by a compensatory pause.
Question 7: A patient's rhythm strip shows grouped beating with progressively lengthening PR intervals until a QRS is dropped. This pattern is called:
- Mobitz Type II
- Wenckebach (Mobitz Type I) (Correct answer)
- Complete heart block
- First-degree AV block
Correct answer: Wenckebach (Mobitz Type I)
Wenckebach (Mobitz Type I) is characterized by progressive PR interval prolongation until a ventricular beat is dropped.
Beat Reading Heart Beat Reading 3
Which of the following is the correct sequence of normal cardiac electrical conduction?