Premature junctional contraction

Premature junctional contractions (PJCs) are premature cardiac electrical impulses originating from the atrioventricular node of the heart or "junction." This area is not the normal but only a secondary source of cardiac electrical impulse formation. These premature beats can be seen occasionally in healthy subjects and more commonly in some pathological conditions, typically in the case of cardiac drug toxicity, electrolyte imbalance, mitral valve surgery and cold water immersion. If more than two such beats are seen, then the condition is termed junctional rhythm. On the surface ECG, premature junctional contractions will appear as a normally shaped ventricular complex or QRS, not preceded by any atrial complex or P wave or preceded by an abnormal P wave with a shorter distance or interval between the P wave and the QRS. Rarely, the abnormal P wave can follow the QRS.