Sinus arrest

Introduction

Sinus arrest is one of the possible manifestations of sinus node dysfunction or it can be a result of high vagal tone, drug effect, hypoxia/ischemia or electrolyte dysbalance. 

In sinus arrest the sinoatrial node (SA) node is unable to produce a beat - no P wave is present. 

Failure to generate a beat results in a pause, that by definition, has to last 2 seconds or more. 

If the SA node remains nonfunctional, an escape rhythm arises. Possible escape rhythms include mainly atrial, junctional, and ventricular rhythms.

Management depends on the underlying cause. All reversible causes should be treated first. If sinus arrest is a manifestation of sinus node dysfunction, a pacemaker implantation should be considered.

ECG characteristics

  • one lead is sufficient to establish the diagnosis
  • no atrial activity (= no P waves) on ECG for >2 seconds
  • the pause may be followed by:
    - sinus rhythm
    - escape rhythm (3 or more beats constitute a rhythm)
       - atrial
       - junctional
       - ventricular

ECG 1 Examples of sinus arrest

  • The first case represents sinus bradycardia followed by sinus arrest with subsequent sinus beat
  • The second case represents a post atypical flutter pause followed by sinus beat

References

  1. https://www.ncbi.nlm.nih.gov/books/NBK470599/
  2. https://ecgwaves.com/topic/sinus-node-dysfunction-snd-sick-sinus-syndrome-sss/
  3. https://litfl.com/sinus-node-dysfunction-sick-sinus-syndrome/
  4. https://en.ecgpedia.org/index.php?title=Sick_Sinus_Syndrome