Escape Beats Flashcard

B. Rationale: The atrioventricular junction has an inherent rate of 40–60 bpm. Therefore, a junctional escape rhythm has a rate between 40–60 bpm. It is a fail-safe mechanism rather than an arrhythmia and is also known as a “passive” junctional rhythm. The junctional escape rhythm is a regular rhythm with regular R-R intervals. The P wave morphology is inverted, and that may occur before, after, or be hidden within the QRS complex. An inverted P wave that precedes the QRS complex should have a PR interval of < 120 milliseconds. The ventricular conduction is normal with a QRS complex that lasts < 120 milliseconds. A ventricular escape rhythm has a lower rate, between 20–40 bpm.

Answer option A: A sinoatrial escape rhythm occurs when the action potential produced by the SA node is blocked.
Answer option C: A first-degree AV block appears as a prolonged PR interval, longer than 0.20 seconds.
Answer option D: A second-degree AV block occurs when there are intermittently conducted P waves without progressive prolongation of the PR interval.

B. Rationale: An idioventricular rhythm is produced by an escape beat. The escape beat is caused by a failure of one of the higher pacemaker sites, resulting in a ventricular focus taking over and forming an idioventricular rhythm. The ventricles have an inherent rate of 20–40 bpm, so an idioventricular rhythm may have this rate but slower rates may also be observed. If this occurs, the idioventricular rhythm is said to be an agonal rhythm because the heart is at the brink of death. An accelerated idioventricular rhythm is also possible when this rate goes above 40 bpm.

Answer option A: A premature ventricular beat is an event where electrical conduction is initiated by the Purkinje fibers in the ventricles rather than the SA node.
Answer option C: Sinus bradycardia presents as a normal sinus rhythm with a rate of 60 bpm or less.
Answer option D: Wenckebach is also known as a second-degree AV block type I. In this dysrhythmia, there are intermittently nonconducted P waves with a prolonged PR interval.