Arrhythmia Recognition:
Premature Junction Contractions
Rate: Usually single events
Regularity: Regular with an event
P wave: Variable
Morphology: Inverted
Upright in II, III, aVF: Inverted
P:QRS Ratio: Variable
PR Interval: Short, if present
QRS Width: Normal
Grouping: None
Dropped Beats: None

Note: Normally, PJCs are benign and cause no hemodynamic compromise. To tell the difference between a PAC and a PJC, look at the following four points. 1. Always look for morphological variation in the preceding T-wave which could indicate a buried P-wave (PAC). 2. PACs usually have a non-compensated pause. PJCs can have either compensatory or non-compesenatory pauses. If there is a compensatory pause, then it is definitely a PJC. 3. Inverted P-waves in Leads II, III and aVF with short PR intervals are usually indicative of PJCs. 4. Look for aberrancy in the QRS to distinguish between PJC and PVC. If the beats start in the same direction then change, it’s a PJC. If they start in opposite directions, then it’s a PVC.

Strip: This strip shows a nice sinus rhythm clipping along at 80 BPM. The cadence of the ventricular complexes is broken up by a premature complex that is narrow and similar in morphology to the rest of the complexes. This is obviously a PJC. The cadence of the atrial complexes, however, is not broken and persists right through the PJC making this a compensatory pause. Notice the buried upright P wave within the PJC (blue arrow). The fact the P wave is upright means that it did not come from the PJC.

Differential Diagnosis:
1. Idiopathic and benign
2. Anxiety
3. Fatigue
4. Drugs: nicotine, alcohol, caffeine, etc.
5. Heart disease
6. Electrolyte disorders