What is Sinus Arrhythmia?

Sinus Arrhythmia in ECG

Sinus arrhythmia is when the sinus node rate changes with the respiratory cycle during inspiration and expiration. This is common in young, healthy individuals and has no clinical significance. In this article, we’ll be discussing what sinus arrhythmia is and how you can identify it in ECG readings.  


Sinus Arrhythmia

Sinus arrhythmia is a type of arrhythmia (abnormal heart rhythm). For the most common type of sinus arrhythmia, the time between heartbeats may be slightly shorter or longer, depending on whether you inhale or exhale. The heart rate increases when you inhale and slows down when you exhale. This arrhythmia is considered normal. This usually shows that your heart is healthy. Sinus arrhythmia is a variation of normal sinus rhythm characterized by an irregular rate of change in the R-R interval greater than 0.12 seconds. In addition, P waves are usually monomorphic with a pattern consistent with atrial activation originating from the sinoatrial node.


Types of sinus arrhythmia


Sinus Arrhythmia_Types
Types of sinus arrhythmia

Non-respiratory sinus arrhythmia

On ECG results, non-respiratory sinus arrhythmia may look like respiratory sinus arrhythmia, but this type of person usually:

  • Head or neck injury.
  • Taking too much digoxin.
  • Have heart disease.


Respiratory sinus arrhythmia

Respiratory sinus arrhythmia is normal because you are breathing. When you breathe, your heart rate goes up. When you exhale, it slows down. The time between each heartbeat is called the P-P interval. In most people, there are small changes of less than 0.16 seconds. In the case of respiratory sinus arrhythmia, when a person exhales, the P-P interval is usually longer than 0.16 seconds.


Ventricular sinus arrhythmia

Professionals can identify ventricular sinus arrhythmias by looking at electrocardiogram (EKG or ECG) results. People with this type of sinus arrhythmia usually have a third-degree atrioventricular block.


Sinus Arrhythmia in ECG

Sinus Arrhythmia in ECG
Sinus Arrhythmia and ECG

The ECG criterion for diagnosing sinus arrhythmia is a change in the P-P interval of at least 0.12 seconds or 120 milliseconds from one beat to the next. If sinus arrhythmia doesn’t occur in young people and isn’t accompanied by breathing, there is a possibility that it might be a sign of sick sinus syndrome or SSS.


Sick Sinus Syndrome

Sick sinus syndrome(or SSS) is an abnormal heart rhythm caused by the sinus node. This happens when the sinus node scars and is replaced by fibrous tissue over time. SSS affects older adults and gender equality more commonly. While SSS may be asymptomatic in some cases, it can also cause a person to experience symptoms like fainting, fatigue, shortness of breath, and heart palpitations. Treatment usually includes the use of a pacemaker. If left untreated, SSS can have serious consequences for a person’s health.

Cardiac arrhythmias that are associated with SSS include:

  • Atrial fibrillation or Afib
  • Severe sinus bradycardia
  • Tachycardia-bradycardia syndrome, also known as bradycardia syndrome
  • Sinus outlet obstruction or sinus arrest

The most common way to diagnose an arrhythmia is to record the heart rhythm electronically using a machine called an electrocardiogram (ECG or EKG).

An electrocardiogram, or EKG, measures several different aspects of the heart, including heart rate, rhythm, and heartbeat interval. Heart rate per minute is normal (60-100); however, this rate increases during inspiration and then decreases during expiration. 

In most cases of respiratory sinus arrhythmia, the heart rate per minute is usually normal. However, the time between each heartbeat can vary, which can indicate sinus arrhythmia. The time between each beat gets shorter as a person breathes in and longer as they breathe out. There is usually more than a 0.12-second variation between the longest and shortest intervals. This will give doctors the clearest indication that the patient has sinus arrhythmia


Rhythm criteria in ECG for sinus arrhythmia

  • Irregular rhythm is at least a 0.12-second variation between longest and shortest R-R intervals.
  • P waves are normal.
  • PR intervals are normal, and each P wave is followed by a normal QRS complex.
  • QRS complex has a normal width.
Rhythm criteria in ECG
Rhythm criteria in ECG for sinus arrhythmia

Sinus arrhythmias are not associated with the sinus cavities of the face but instead associated with the sinuses or sinus nodes of the heart. The sinus node(also called the sinoatrial node) is located in the upper chamber on the right side of the heart, called the right atrium. The sinus node is known as the heart’s natural “pacemaker,” which means it’s responsible for the rhythm of a person’s heartbeat. Normal sinus rhythm is the regular heart rhythm found in the majority of healthy individuals. Sinus arrhythmia is an irregular heart rhythm that originates in the sinus node.


Factors that can cause sinus arrhythmia

  • Certain natural drugs and recreational drugs
  • Having a viral disease
  • Too much smoking/tobacco use
  • Excessive exercise
  • Excessive caffeine intake
  • Has had a previous heart attack or heart failure
  • Drinking alcohol
  • Being overweight
  • Having an unhealthy diet
Factors that can cause sinus arrhythmia
Factors that can cause sinus arrhythmia

Risks of having sinus arrhythmia

Sinus arrhythmia is common in children and sometimes in adults. Children with respiratory sinus arrhythmia tend to have fewer symptoms as they age without treatment. While the exact cause of respiratory sinus arrhythmia is unknown, researchers believe it may increase efficiency or allow the heart to do less work while maintaining correct blood gas levels. Cases of respiratory sinus arrhythmia in children and young adults usually improve with age without treatment. This is because a child’s heart is still developing, and changes in the heart can lead to respiratory sinus arrhythmia. If the child has respiratory sinus arrhythmia, the doctor may want to monitor it, but may not provide any treatment unless the problem becomes severe, causes symptoms, or persists into adolescence.

Older adults with severe cardiac arrhythmias may need a pacemaker. People with sleep apnea are also more likely to have arrhythmias, including sinus arrhythmias.


Treatment for sinus arrhythmia

Since respiratory sinus arrhythmia is normal, people without symptoms rarely need treatment. For non-respiratory sinus arrhythmia or ventricular sinus arrhythmia, the doctor needs to treat the medical condition that causes the sinus arrhythmia, but this is a case-by-case basis, professionals will still need to run some tests before they could suggest a treatment.