Junctional rhythm: This is a rhythm which originates in the AV node, and involves retrograde (backward) and antegrade (normal direction) transmission (Figure 18).
Idioventricular rhythm: This is a rhythm which originates in the ventricle (Figure 19). Such a rhythm is very slow (<40 per min), the QRS complex is wide, bizarre, and notched, and the T wave is inverted. Ventricular pacemakers have the slowest automaticity in the hierarchy of pacemakers. The QRS complex is wide because conduction must occur from the site of origin through the ventricular tissue, from cell to cell, not along the specialized conduction pathways. It is notched because first the left ventricle is depolarized and then the right ventricle, or vice versa. The T wave is inverted because repolarization is abnormal. There may or may not be a P wave.
Back to Index