Sinus arrhythmia
Every beat is a normal sinus beat, but the rate speeds up and slows down with breathing, so the R-R intervals stretch and shorten in a smooth, repeating wave.
How to identify Sinus arrhythmia
- Rate
- Usually 60-100
- Rhythm
- Irregular in a smooth, repeating wave
- P waves
- Upright, one before every QRS
- PR interval
- 0.12-0.20 s, constant
- QRS
- Under 0.12 s
- Clincher
- The rate speeds up and slows down with breathing.
- Common causes
- Respiration.
Rhythms it gets mistaken for
Sinus arrhythmia vs Normal sinus rhythm
Sinus arrhythmia has a rate that speeds up and slows down in a smooth, repeating wave. With normal sinus rhythm you would see a regular rhythm.
Sinus arrhythmia vs Atrial fibrillation
Sinus arrhythmia has one upright P wave before every QRS, all the same shape. With A-fib you would see no P waves, only a wavy, chaotic baseline. It starts in the SA node: a sinus rhythm.
Sinus arrhythmia vs Premature atrial complexes (PACs)
Sinus arrhythmia has one upright P wave before every QRS, all the same shape. With PACs you would see an early P wave that looks different from the others. It starts in the SA node: a sinus rhythm.
Treatment by certification level
Open your level. Treat the patient, not the strip.
Paramedic
No rhythm treatment needed.
- Treat the patient in front of you, not the strip.
AEMT
Pulse present and stable.
- Oxygen only if hypoxic or short of breath, IV access, monitoring.
- Acquire and transmit a 12-lead ECG. Interpreting it is a Paramedic skill.
- Transport and reassess. Request a paramedic if the patient worsens.
EMT
Pulse present: assess and support.
- Treat the patient, not the rhythm name: airway, breathing, circulation, vital signs.
- Oxygen if the SpO2 is under 94%, the patient is short of breath, or shows signs of shock.
- Request ALS and transport promptly. Reassess on the way.
An AED goes only on a patient who is unresponsive, not breathing and pulseless. It cannot feel a pulse, so on a patient with a pulse it can advise a shock that would do harm.