CCRN Cardiac Rhythm Interpretation and Management

Question 1

An ICU patient's monitor shows a regular rhythm at 150 bpm with narrow QRS complexes and a classic sawtooth baseline pattern. What is the most likely rhythm?

Accepted Answer

Atrial flutter with 2:1 block

Answer

Atrial flutter typically fires at 300 bpm; with 2:1 block the ventricular rate is 150 bpm, and the sawtooth (flutter) waves are the hallmark finding.

Question 2

Which ECG change is the earliest indicator of hyperkalemia in a critically ill patient?

Accepted Answer

Peaked (tall, narrow) T waves

Answer

Peaked T waves are the earliest ECG manifestation of hyperkalemia, appearing before PR prolongation, QRS widening, or the sine wave pattern seen in severe cases.

Question 3

Which ECG characteristic definitively identifies a third-degree (complete) AV block?

Accepted Answer

Completely independent atrial and ventricular rates with no relationship

Answer

In complete heart block, the atria and ventricles fire independently because no impulses conduct through the AV node, producing dissociated P waves and QRS complexes.

Question 4

A normal PR interval on a standard ECG measures:

Accepted Answer

0.12–0.20 seconds

Answer

The normal PR interval ranges from 0.12 to 0.20 seconds (3–5 small boxes); values above 0.20 indicate first-degree AV block.

Question 5

A patient's rhythm strip shows an irregularly irregular ventricular response, absent distinct P waves, and an estimated atrial activity rate of 400–600 bpm. What is this rhythm?

Accepted Answer

Atrial fibrillation

Answer

Atrial fibrillation is characterized by chaotic atrial activity at 400–600 bpm, absent organized P waves, and an irregularly irregular ventricular response.

CCRN Review Practice Test

CCRN Review Practice Test

CCRN Cardiac Rhythm Interpretation and Management