Junctional Rhythm - ECG
Junctional rhythm is generated in the AV node. The rhythm can occur in this location when the SA node function is disrupted (in this case, it is referred to as replacement junctional rhythm and it tends to have a lower frequency than 60 bpm) or when the electric impulse starts to occur in AV node in a too high frequency (in this case, we call it junctional tachycardia). The result is a regular rhythm with narrow QRS complexes. In some cases, the QRS complexes are preceded by negative P waves (as the electric signals spread through atria from the AV node). In other cases, the P waves are invisible, because they are hidden behind the QRS complexes.
This is one of many appearances of a junctional rhythm. In this case, the P-wave is visible, but it has negative amplitude (red circle). The heart rate is slower than normal, assuming the normal ECG paper speed; the heart rate may be approximately 50 bpm.
Conclusion: Probably the most important is the replacement junctional rhythm that can occur when there is a damage of the SA node (e.g. by myocardial infarction). This junctional rhythm is quite slow and may cause symptoms of bradycardia (such as syncope) and sometimes it must be solved by a pacemaker implantation. Junctional tachycardia is very similar to regular supraventricular tachycardia AVNRT and it is also similarly treated.