Premature Junctional Contractions

Also known as PJCs
Junctional (ectopic) beats that occur before normal sinus beats and interrupt the underlying rhythm
Impulses generated in the atrioventricular (AV) junction
Commonly result from enhanced automaticity in junctional tissue or the bundle of His
Retrograde depolarization of atria, causing an inverted P wave before, after, or hidden within the QRS complex
Normal ventricular depolarization

Memory jogger

To remember the location of the P wave in PJCs, recall that A comes before V, or V comes after A, in the term AV junction:

If the atria (A) depolarize first, the P wave appears before the QRS complex.
If the ventricles (V) depolarize first, the P wave appears after the QRS complex.

Identifying a PJC

This rhythm strip illustrates PJC. Look for these distinguishing characteristics:

Rhythm

Irregular atrial and ventricular rhythms

Rate

100 beats/min

P wave

Inverted and precedes the QRS complex with PJC; otherwise normal configuration

PR interval

0.14 second for the underlying rhythm and 0.06 second for the PJC

QRS complex

0.06 second

T wave

Normal configuration

QT interval

0.36 second

Other

Pause after PJC

P wave inversion

Look for an inverted P wave in leads II, III, and aV_F. Depending on when the impulse occurs, the P wave may fall before, during, or after the QRS complex. (See Identifying a PJC.) If it falls during the QRS complex, it's hidden. If it comes before the QRS complex, the PR interval is less than 0.12 second.

Because the ventricles are usually depolarized normally, the QRS complex has a normal configuration and a normal duration of less than 0.12 second. The T wave and the QT interval are usually normal.

What Causes It ⬆ ⬇

What causes them

Chronic obstructive pulmonary disease
Coronary artery disease
Digoxin toxicity
Electrolyte imbalances
Heart failure
Hyperthyroidism
Inferior-wall myocardial infarction (MI)
Inflammatory changes in the AV junction after heart surgery
Myocardial ischemia
Pericarditis
Stress
Valvular heart disease

Locating the P wave

When specialized pacemaker cells in the AV junction take over as the dominant pacemaker of the heart, the P wave becomes inverted because the atria depolarize in a retrograde fashion. These illustrations show the various locations of P waves in junctional arrhythmias, depending on the depolarization sequence of the atria and ventricles.

If the atria depolarize first, the P wave will appear before the QRS complex.

If the ventricles depolarize first, the P wave will appear after the QRS complex.

If the ventricles and atria depolarize simultaneously, the P wave will be hidden in the QRS complex.

Triggers

Alcohol
Caffeine
Nicotine

What to Look for ⬆ ⬇

Usually no symptoms
Possible feeling of palpitations or skipped beats
Hypotension from a transient decrease in cardiac output if PJCs are frequent enough

How It's Treated ⬆

How they're treated

PJCs usually don't require treatment if the patient is asymptomatic.
If the patient is symptomatic, the underlying cause should be treated.
In patients taking digoxin, PJCs are a common early sign of toxicity. If the patient has digoxin toxicity, stop the drug and monitor the patient's drug levels as ordered.
Monitor the patient's cardiac rhythm for frequent PJCs, which may indicate junctional irritability and can lead to a more serious arrhythmia such as junctional tachycardia.
Monitor the patient for hemodynamic instability.
If ectopic beats occur frequently because of a trigger such as caffeine intake, the patient should decrease or eliminate the trigger.

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Introduction ⬇

What Causes It ⬆ ⬇

What to Look for ⬆ ⬇

How It's Treated ⬆