Sinus Arrest - Sinus Rhythms.
- Sinus Arrest occurs when there is a sudden absence of electrical activity initiated by the SA node. This results in a pause in the electrical activity seen on the tracing. Remember, no electrical activity = no depolarization and contraction. Hence, a drop in blood pressure.
- The longer the pause, the further the blood pressure will drop.
- A pause of six-seconds is considered a medical emergency and emergency procedures must be initiated.
- The rhythm typically will demonstrate constant R to R intervals prior to and following the pause. This pause results in the rhythm tracing presenting as irregular.
- It is important to measure the duration of the pause and report this information along with the frequency of the pauses if there are more than one.
- The pause is measured by placing your caliper tips on the last R wave just prior to the pause and the R wave immediately following the pause. Count the number of small boxes and multiply by 0.04 second. This will be reported as part of the interpretation.
Analyze this tracing using the five steps of rhythm analysis.
- Rhythm: Irregular
- Rate: 40 bpm
- P wave: upright and uniform
- PR interval: 0.16 sec
- QRS: 0.10 sec
- Interpretation: Sinus Arrest, 3.52 second pause
Authors and ReviewersAuthored by Thomas O'Brien
Medically reviewed by Dr. Jonathan Keroes, MD, Cardiology
Last Update: 11/8/2020