CRAT Atrial Arrhythmia Identification 2 — Questions and Answers
Question 1: Which atrial arrhythmia is characterized by a sawtooth pattern at a rate of 250-350 bpm on the ECG?
- Atrial flutter (Correct answer)
- Atrial fibrillation
- Atrial tachycardia
- Multifocal atrial tachycardia
Correct answer: Atrial flutter
Atrial flutter produces the classic sawtooth flutter waves (F waves) at 250-350 bpm, best visible in leads II, III, aVF, and V1.
Atrial flutter arises from a reentrant circuit in the right atrium, creating uniform, regular flutter waves at 250-350 bpm. Ventricular rate depends on the AV conduction ratio; 2:1 conduction produces a ventricular rate near 150 bpm.
Question 2: In atrial fibrillation, which ECG finding is most characteristic?
- Irregularly irregular rhythm with absent distinct P waves (Correct answer)
- Regular rhythm with sawtooth flutter waves
- Regularly irregular rhythm with delta waves
- Regular rhythm with prolonged PR interval
Correct answer: Irregularly irregular rhythm with absent distinct P waves
Atrial fibrillation produces an irregularly irregular ventricular rhythm and replaces distinct P waves with chaotic fibrillatory f waves at 350-600 bpm.
In atrial fibrillation, multiple chaotic re-entrant wavelets depolarize the atria at 350-600 bpm, producing an irregular baseline without discernible P waves. The AV node is bombarded randomly, resulting in an irregularly irregular ventricular response.
Question 3: A rhythm strip shows P wave morphology varying in at least three different shapes with an irregular rate above 100 bpm. What arrhythmia is present?
- Multifocal atrial tachycardia (Correct answer)
- Atrial fibrillation
- Wandering atrial pacemaker
- Atrial flutter with variable block
Correct answer: Multifocal atrial tachycardia
Multifocal atrial tachycardia (MAT) is defined by three or more distinct P wave morphologies, an irregular rhythm, and a rate greater than 100 bpm.
MAT occurs when multiple ectopic atrial pacemakers fire at varying rates, each producing a distinct P wave morphology. The rate exceeds 100 bpm and the rhythm is irregular. It is most commonly associated with severe pulmonary disease, hypomagnesemia, and hypoxia.
Question 4: Paroxysmal supraventricular tachycardia (PSVT) most commonly has which ventricular rate range?
- 150-250 bpm (Correct answer)
- 60-100 bpm
- 100-120 bpm
- 250-350 bpm
Correct answer: 150-250 bpm
PSVT characteristically presents with a sudden-onset, regular tachycardia at 150-250 bpm with narrow QRS complexes unless aberrant conduction is present.
PSVT, most often caused by AVNRT or AVRT, produces a regular narrow-complex tachycardia at 150-250 bpm. Onset and termination are abrupt (paroxysmal). P waves may be buried in or just after the QRS complex.
Question 5: A P wave with negative deflection in lead I and positive deflection in aVR most likely indicates which condition?
- Ectopic atrial rhythm originating from the left atrium (Correct answer)
- Normal sinus rhythm
- Right atrial enlargement
- Junctional tachycardia
Correct answer: Ectopic atrial rhythm originating from the left atrium
A negative P wave in lead I and positive in aVR suggests retrograde or left-sided atrial activation, characteristic of a left atrial ectopic focus.
Normal sinus rhythm produces upright P waves in lead I and inverted P waves in aVR. When an ectopic pacemaker in the left atrium fires, the wavefront travels right to left, inverting the P in lead I and making it positive in aVR. This helps localize the ectopic pacemaker.
Question 6: Atrial flutter with 4:1 AV conduction produces a ventricular rate of approximately how many bpm if the atrial rate is 300 bpm?
- 75 bpm (Correct answer)
- 150 bpm
- 100 bpm
- 50 bpm
Correct answer: 75 bpm
With an atrial flutter rate of 300 bpm and 4:1 conduction, 300 divided by 4 equals 75 bpm.
In atrial flutter, the AV node allows only a fraction of flutter waves to reach the ventricles. A 4:1 ratio means one of every four flutter waves is conducted. At 300 bpm atrial rate, ventricular rate becomes 75 bpm, which may appear almost normal and can be deceptive on a rhythm strip.
CRAT Atrial Arrhythmia Identification 2
Which atrial arrhythmia is characterized by a sawtooth pattern at a rate of 250-350 bpm on the ECG?