Atrial Arrhythmia Identification Flashcards

A patient's ECG strip shows a narrow complex tachycardia at a regular rate of 150 bpm. The baseline has a characteristic "saw-tooth" appearance, which is most prominent in leads II, III, and aVF. No clear P waves are discernible. What is the most likely atrial arrhythmia?

Answer: Atrial Flutter

Atrial Flutter is characterized by a rapid, regular atrial rate (around 250-350 bpm) that creates a 'saw-tooth' pattern of flutter waves. [1, 9, 25] A 2:1 AV block is very common, resulting in a regular ventricular rate of approximately 150 bpm. [7, 25] Atrial Fibrillation is irregularly irregular with no discernible P waves, Sinus Tachycardia has normal P waves preceding each QRS, and Multifocal Atrial Tachycardia is irregular with at least three different P wave morphologies. [4, 19, 27]

Which of the following ECG findings is essential for the diagnosis of Multifocal Atrial Tachycardia (MAT)?

Answer: At least three different P wave morphologies in the same lead

The defining criteria for Multifocal Atrial Tachycardia (MAT) are a heart rate greater than 100 bpm, an irregular rhythm, and the presence of at least three distinct P-wave morphologies in the same lead. [3, 27, 28] A rate less than 100 bpm with these P wave characteristics would be a Wandering Atrial Pacemaker. [28, 29] While the rhythm is irregular, it is not 'regularly irregular', and it does have an isoelectric baseline between P waves. [3]

A rhythm strip displays an irregularly irregular rhythm with no identifiable P waves and a variable ventricular rate of 120-140 bpm. The baseline appears chaotic and wavy. These findings are most consistent with:

Answer: Atrial Fibrillation

Atrial Fibrillation is characterized by a chaotic atrial activity leading to an irregularly irregular ventricular response, the absence of P waves, and a fibrillating baseline. [4, 8, 26] Atrial flutter with variable block is also irregularly irregular, but it would show organized 'saw-tooth' flutter waves. [7, 8] Wandering Atrial Pacemaker has visible P waves of different morphologies and a rate under 100 bpm. Atrial Tachycardia is typically a regular rhythm with abnormal P waves. [16, 28]

A technician observes a rhythm strip where the underlying sinus rhythm is interrupted by a single beat that occurs earlier than expected. This premature beat has a P wave with a different morphology from the sinus P waves, followed by a normal QRS complex. What is this single beat called?

Answer: Premature Atrial Contraction (PAC)

A Premature Atrial Contraction (PAC) is an ectopic beat originating from the atria, causing it to occur early. [5, 13] Its key features are a premature P wave with an abnormal shape compared to sinus P waves, followed by a typically normal QRS complex. [5, 24] A PJC originates in the AV junction and usually has an inverted or absent P wave. A PVC originates in the ventricles and has a wide, bizarre QRS. Atrial Bigeminy refers to a pattern where every other beat is a PAC, not the single beat itself. [5]

A patient is admitted with palpitations. The ECG shows a regular, narrow-complex tachycardia at 130 bpm. There is a P wave before each QRS, but the P wave morphology is different from the patient's baseline sinus rhythm ECG, being inverted in lead III. The PR interval is constant. What is the most likely diagnosis?

Answer: Atrial Tachycardia

Atrial Tachycardia originates from a single ectopic focus in the atria, resulting in a regular rhythm with abnormal P waves that have a consistent morphology, different from the sinus P waves. [2, 16] Sinus Tachycardia would have normal P wave morphology for that patient. [19] Atrial Fibrillation is irregular and lacks P waves, and Atrial Flutter has a characteristic saw-tooth baseline. [4, 9]

When analyzing a rhythm strip for atrial fibrillation, which characteristic is the most definitive indicator of this arrhythmia?

Answer: An irregularly irregular R-R interval with no discernible P waves

The hallmark of Atrial Fibrillation is the combination of an irregularly irregular rhythm (varying R-R intervals) and the absence of clear, discernible P waves, which are replaced by a chaotic or fibrillating baseline. [4, 8, 18] While the rate is often rapid, it can be controlled, and fibrillatory waves are not always visible. [4] A narrow QRS is typical but can be wide with aberrant conduction, so it is not the most definitive feature. [4]