Junctional Dysrhythmias

Junctional rhythms can be either simple junctional rhythms or atrioventricular blocks where electrical activity is impaired at the AV node.
The topic of blocks will be discussed in a future session.
Current focus: junctional rhythms occurring due to SA node failure, where the AV node acts as the escape pacemaker.

Less frequent than sinus or atrial dysrhythmias.
They exhibit a regular rhythm with a consistent R to R interval.
P Waves can show three different patterns:
- Inverted P Waves occurring before the QRS complex.
- Absent P Waves (none present).
- Inverted P Waves following the QRS complex.
Reasons for the patterns of P Waves:
- When the AV node generates an impulse, the electrical impulse travels forward to the ventricles but also backward to the atria, causing inverted P Waves since they move away from the positive electrode.
- An inverted P Wave before the QRS indicates that atrial depolarization occurs before ventricular depolarization.
- An inverted P Wave after the QRS indicates ventricular depolarization happens before atrial depolarization.
- The absence of P Waves means simultaneous depolarization of the atria and ventricles, but the ventricular activation usually dominates in the rhythm strip.

The QRS complex is typically narrow (indicating origin above ventricles).
Summary criteria for junctional rhythms:
- Regular rhythm.
- Inverted P Waves (before, after, or absent with narrow QRS).

Junctional rhythms typically have a heart rate of 40 to 60 beats per minute (normal AV node rate).
Heart rate classifications:
- Junctional Bradycardia: Heart rate < 40 bpm.
- Junctional Rhythm (Stable): Heart rate 40 - 60 bpm.
- Accelerated Junctional Rhythm: Heart rate 60 - 100 bpm.
- Junctional Tachycardia: Heart rate > 100 bpm.

Definition: Junctional rhythms originating from the AV node with a rate < 40 beats per minute.
Rhythm: Regular R to R interval meets prior criteria (P Waves orientation/instruction).
Cause: Occurs due to non-firing SA node.
Treatment:
- Atropine: Administered to increase heart rate, particularly in bradycardic situations.
- Transcutaneous or Temporary Pacemaker: Considered when bradycardia is severe.
- Dopamine or Epinephrine: Other options when further intervention is needed.

Heart rate: 40 - 60 bpm.
Maintains regular rhythm with prior defined characteristics.
Symptoms often mild; assess medications possibly impacting heart rate.
Treatment:
- Consider reducing or holding any medications that induce bradycardia.

Rate: 60 - 100 bpm.
Rules of P Waves and narrow QRS remain applicable.
Causes include SA node failure or irritability of the AV node due to chemicals or other factors.
Treatment: Typically monitoring; address any underlying chemical irritable contributors.

Heart rate: > 100 bpm, meeting previously established criteria without P Waves identification.
Possible causes: SA node ineffective, irritability of AV node, or Digitoxicity.
Digitoxicity signs include:
- Hypotension.
- Gastrointestinal symptoms like nausea and loss of appetite.
- Bradycardia or tachycardia is possible, often presenting alongside symptoms.
Treatment considerations involve hemodynamic stability assessment, including blood pressure and neurological status during tachycardia.
Medications: Beta-blockers and calcium channel blockers may be used for rate control.

Definition: Similar to premature atrial contractions (PACs) but originating from the AV node.
Characteristics: Early beat that disrupts the rhythm but fits within underlying patterns.
P Wave Presence: Typically absent; if present, it’s normally inverted.
Treatment: Typically none, unless underlying causes are identifiable, in which case, they are addressed.

Understanding junctional rhythms involves recognizing P Wave patterns, regularity, and heart rate implications. Treatments often aim for heart rate stability and symptomatic management.