Diagnostic criteria

  P wave morphology is normal however PP intervals change more than 0.16 seconds (4 small squares).

  Respiration affects the frequency of impulses originating from the sinus node:

      the heart rate increases during inspiration and decreases during expiration.

  Since the impulses originate from the sinus node, P waves look like each other and

      are positive in leads I and II while negative in lead aVR.

  Each P wave is followed by a QRS complex.

      Since PP intervals are not equal, the RR intervals also are not equal.

  Sinus arrhythmia can be observed more frequently when sinus rate is slow.

  Since it is affected by vagal tone, sinus arrhythmia cannot be observed in patients who have

      received atropin or who have undergone vagotomy (after heart transplantation, etc).




Causes

  Respiratory sinus arrhythmia: inspiration inhibits vagal tone resulting in

      an increase in heart rate and expiration results in decreased heart rate.

  Coronary artery disease.

  Increased intracranial pressure.




Clinical significance

  Especially more prevalent in children and adolescents.

  Sinus arrhythmia has no clinical significance.




Reference

  Curr Probl Cardiol 2004;29:357-432.





ECG 1. Sinus arrhthmia. P-P intervals are not equal.

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ECG 2. Sinus arrhythmia in a girl of 11 years old. P waves are identical.

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ECG 3. Sinus arrhythmia in an 18 years old male.

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ECG 4.
Sinus arrhythmia detected during the Holter recording of an apparently healthy 22 years-old man.

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ECG 5. Sinus arrhythmia in an apparently healthy young girl.

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ECG 6. Respiratory sinus arrhythmia is seen in an apparently healthy 3 years-old girl.

Pediatric cardiologist Dr. Mahmut Gokdemir has donated the above ECG to our website.

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ECG 7. Respiratory sinus arrhythmia is seen in an apparently healthy 6 years-old girl.

Pediatric cardiologist Dr. Mahmut Gokdemir has donated the above ECG to our website.

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ECG 8a. The ECG above is from a 62 years-old woman with baseline drift, sinus arrhythmia and low amplitude P waves.
The diagnosis may be atrial fibrillation at first glance.

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ECG 8b. The ECG was recorded again. Sinus arrhythmia still persists but lesser baseline drift permits easy recognition
of P waves.

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ECG 8c. Re-recording of the ECG at a calibration of 20 mm/mV shows P waves more clearly.

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ECG 9. Respiratory sinus arrhythmia is seen in the above ECG of a 15 years-old male.

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