ECG Rhythm Analysis 2

Question 1

A patient's ECG shows a regular rhythm at 150 bpm with narrow QRS complexes and no visible P waves. What is the most likely rhythm?

Accepted Answer

Atrial flutter with 2:1 block

Answer

Atrial flutter with 2:1 block classically presents at 150 bpm with narrow QRS and flutter waves often hidden in the T wave or QRS complex.

Question 2

Which ECG finding is the hallmark of Wolff-Parkinson-White (WPW) syndrome during sinus rhythm?

Accepted Answer

Delta wave with short PR interval

Answer

WPW is characterized by a delta wave (slurred QRS upstroke) and a short PR interval due to ventricular pre-excitation via an accessory pathway.

Question 3

A rhythm strip shows regularly spaced P waves at 75 bpm with QRS complexes at 40 bpm that bear no relationship to P waves. This describes:

Accepted Answer

Third-degree (complete) heart block

Answer

Complete (third-degree) heart block is defined by complete AV dissociation where P waves and QRS complexes march independently at different rates.

Question 4

On a rhythm strip, the RR interval measures 20 large boxes. What is the heart rate?

Accepted Answer

15 bpm

Answer

Using the 300 method: 300 ÷ 20 large boxes = 15 bpm.

Question 5

Torsades de pointes is most directly associated with which ECG abnormality?

Accepted Answer

Prolonged QTc interval

Answer

Torsades de pointes is a polymorphic ventricular tachycardia that characteristically occurs in the setting of a prolonged QTc interval.

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