Sinus Bradycardia

Rhythm             : Regular

Heart Rate       : <60 bpm

P Wave              : Normal, every P wave followed by QRS Complexes

PR Interval     : Normal (0.12 – 0.20 second)

QRS Complexes  : Normal (narrow = 0.06 – 0.12 second)

Sinus Tachycardia

Rhythm             : Regular

Heart Rate       : 100 – 150 bpm

P Wave              : Normal, every P wave followed by QRS Complexes

PR Interval     : Normal (0.12 – 0.20 second)

QRS Complexes  : Normal (narrow = 0.06 – 0.12 second)

Sinus Rhythtm

Rhythm             : Regular

Heart Rate       : 60 – 100 bpm

P Wave              : Normal, every P wave followed by QRS Complexes

PR Interval     : Normal (0.12 – 0.20 second)

QRS Complexes  : Normal (narrow = 0.06 – 0.12 second)

Junctional rhythms are pure of heart rhythm originating from the AV node because of the inability of the SA node provides an optimal electrical impulses.

Cardiac rhythms arising from the atrioventricular (AV) junction occur as an automatic tachycardia or as an escape mechanism during periods of significant bradycardia with rates slower than the intrinsic junctional pacemaker.

The AV node (AVN) has intrinsic automaticity that allows it to initiate and depolarize the myocardium during periods of significant sinus bradycardia or complete heart block. This escape mechanism, with a rate of 40-60 beats per minute, produces a narrow QRS complex because the ventricle is depolarized using the normal conduction pathway. An accelerated junctional rhythm (rate >60) is a narrow complex rhythm that often supersedes a clinically bradycardic sinus node rate . The QRS complexes are uniform in shape, and evidence of retrograde P wave activation may or may not be present.

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The other form of Junctional Rhythm :

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