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doi: 10.1097/01.CCN.0000565152.08616.77
Department: Name That Strip
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Figure

Figure

Determine the following:

Rhythm: _______________________________________

Rate: ___________________________________________

P waves: _______________________________________

PR interval: ____________________________________

QRS complex: __________________________________

What's your interpretation?

(Answers on next page)

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Name that strip: Answers

Rhythm: Regular

Rate: 47 beats/minute

P waves: Hidden in QRS complex

PR interval: Not measurable

QRS complex: 0.06 to 0.08 second

Comment: ST segment depression is present

Interpretation: Junctional rhythm

Junctional rhythm is a dysrhythmia originating in the atrioventricular (AV) junction with a rate between 40 and 60 beats/minute. Junctional rhythm is the normal rhythm of the AV junction. Junctional rhythm most often occurs when the heart rate of the dominant pacemaker (usually the sinoatrial node) becomes less than the heart rate of the AV junction. When this occurs, a focus in the AV junction can escape and pace the heart at the inherent firing rate of the AV junction. For this reason, junctional rhythm is sometimes referred to as junctional escape rhythm. Junctional rhythm can also occur following a pause in the underlying rhythm (following sinus arrest or block, after premature beats or nonconducted premature atrial contractions, or during the pause associated with second-degree AV block, Type I).

Junctional rhythm P waves are inverted in lead II (a positive lead) and will occur immediately before or after the QRS complex or be hidden within the QRS complex. The PR interval (if present) is short (0.10 second or less). The QRS complex duration is usually normal. Junctional rhythm has the same ECG features as accelerated junctional rhythm and junctional tachycardia. The rhythm is differentiated from the other junctional rhythms by the heart rate. Junctional rhythm is not a common rhythm.

Junctional rhythm may be seen in acute myocardial infarction (MI), particularly inferior wall MI, increased parasympathetic tone, sinus node dysfunction, and hypoxemia. It can also occur in patients taking digitalis, calcium channel blockers, or beta-blockers.

The slow rate and loss of normal atrial contraction (atrial kick) secondary to retrograde atrial depolarization may cause a decrease in cardiac output. Treatment for symptomatic junctional rhythm includes following the guidelines for clinically unstable bradycardia with a pulse. Treatment should also be directed at identifying and correcting the underlying cause of the dysrhythmia, if possible. All medications should be reviewed and discontinued if indicated.

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Junctional rhythm: Identifying ECG features

Rhythm: Regular

Rate: 40 to 60 beats/minute

P waves: Inverted in lead II and occur immediately before or after the QRS complex, or are hidden within the QRS complex

PR interval: Short (0.10 second or less) if present

QRS complex: Generally normal (0.10 second or less)

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