• Bradyarrhythmia, or slow heart beat < 60 bpm, often arises due to either:
SA node dysfunction or SND (also referred to as sick sinus syndrome or SSS), or
AV node dysfunction (also referred to as AV block)
• In the absence of electrical impulse from the SA node due to SND or conduction block at the AV junction, either a junctional or ventricular automaticity focus can take over and send out electrical impulses thus creating a junctional or ventricular escape rhythm. However, due to their slow inherent rate (40-60 bpm for junctional focus and 20-40 bpm for ventricular focus), the resulting rhythm will be bradyarrhythmia.
An exception is the accelerated junctional rhythm which has a normal-fast heart rate
On the other hand, an atrial escape rhythm will has a normal-fast heart rate because the atrial focus has inherent rate at 60-80 bpm
• In extreme cases, when there is complete sinus exit block or sinus arrest but other automaticity foci fail to take over, the resulting rhythm will be asystole.
