Rhythm Analysis: Atrial/Junctional Flashcards

A CCT is analyzing a rhythm strip and observes an irregularly irregular rhythm, no discernible P waves, and a fibrillatory baseline. The ventricular rate is 130 bpm. Which of the following is the most likely interpretation?

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 fibrillatory baseline on the ECG. [4, 13, 20] Multifocal Atrial Tachycardia would show at least three different P wave morphologies. Atrial Flutter typically has a 'sawtooth' pattern. Junctional Tachycardia is usually regular with absent or inverted P waves.

An ECG tracing shows a regular rhythm at a rate of 48 bpm. There are no visible P waves, and the QRS complexes are narrow (<0.12 seconds). This rhythm is best described as:

Answer: Junctional Escape Rhythm

A Junctional Escape Rhythm originates from the AV junction when the SA node fails to fire. Its intrinsic rate is 40-60 bpm. [5, 8, 12] Key features are a regular rhythm within this rate range, absent or inverted P waves, and narrow QRS complexes. [2, 10, 30] Sinus bradycardia would have upright P waves. A third-degree block would show AV dissociation. An agonal rhythm would be slower and have wide, bizarre QRS complexes.

A patient's rhythm strip displays a heart rate of 80 bpm. The technician notes that there are at least four different P wave morphologies, the R-R interval is irregular, and the PR interval varies. What is this rhythm?

Answer: Wandering Atrial Pacemaker

Wandering Atrial Pacemaker (WAP) is defined by having at least three different P wave morphologies, an irregular rhythm, and a heart rate less than 100 bpm. [1, 11, 15] This indicates that the pacemaker site is shifting between various locations within the atria. If the rate were over 100 bpm, it would be Multifocal Atrial Tachycardia. [11, 15, 32]

Which of the following ECG findings is characteristic of a Premature Junctional Contraction (PJC)?

Answer: An early, narrow QRS complex that may have an inverted or absent P wave.

A Premature Junctional Contraction (PJC) is an early beat originating from the AV junction. Because the impulse travels backward to the atria, the P wave, if visible, will be inverted and can appear before, during (hidden), or after the narrow QRS complex. [2, 18, 26, 31]

A CCT observes a regular, narrow-complex tachycardia at a rate of 170 bpm. There are upright P waves in lead II, but they have a different morphology than the patient's baseline sinus P waves. The PR interval is constant. What is the most likely rhythm?

Answer: Atrial Tachycardia

Atrial Tachycardia originates from a single ectopic focus within the atria, resulting in a regular rhythm with a rate typically between 150-250 bpm. [3, 7, 25] The P waves will have a different shape and axis compared to sinus P waves, reflecting the ectopic origin. [3] Junctional tachycardia would have inverted or absent P waves. Sinus tachycardia would have normal P wave morphology. Atrial fibrillation is irregularly irregular.

A patient is found to have an Accelerated Junctional Rhythm on their ECG. Which of the following heart rate ranges is consistent with this diagnosis?

Answer: 61-100 bpm

Junctional rhythms are classified by their rate. A Junctional Escape Rhythm has a rate of 40-60 bpm (the intrinsic rate of the AV junction). [5, 30] An Accelerated Junctional Rhythm has a rate between 61 and 100 bpm. [2, 5, 8] A rate over 100 bpm from the junction is termed Junctional Tachycardia. [2, 5, 8]