What is a sinus arrhythmia?

A person’s heart should beat with regular intervals, much like the second hand on a clock. An arrhythmia is when there is a problem with the heart’s rhythm, or it beats irregularly. Sinus arrhythmia is one type of arrhythmia.

In this article, we look at what a sinus arrhythmia is, how it is diagnosed, and if it is a health concern. Although different types of sinus arrhythmia will be covered, this article will focus on respiratory sinus arrhythmia.

Definition and types

Sinus arrhythmia does not relate to the sinus cavities in the face but to the sinoatrial or sinus node in the heart.

The sinoatrial node is in the right side of the heart, and dictates a person's heartbeat.
The sinoatrial node is in the right side of the heart, and dictates a person’s heartbeat.

The sinoatrial or sinus node is located in the upper chamber on the right side of the heart, which is called the right atrium.

The sinus node is known as the heart’s natural “pacemaker,” meaning it is responsible for the rhythm of a person’s heartbeats.

Normal sinus rhythm is a regular rhythm found in healthy people.

Sinus arrhythmia means there is an irregularity in the heart rhythm, originating at the sinus node.

In general, sinus arrhythmias can be:

  • Sinus tachycardia, which is a faster heart rate, beating greater than 100 beats per minute.
  • Sinus bradycardia, which is when the heart rate beats slower or less than 60 beats per minute.

Respiratory sinus arrhythmia

Respiratory sinus arrhythmia is effectively benign, meaning that it is not harmful. It occurs when a person’s heart rate relates to their breathing cycle. In other words, when the person breathes in, their heart rate increases, and when they breathe out, the rate decreases.

Respiratory sinus arrhythmia is more common in children than adults and tends to disappear, as they get older.

The time between each heartbeat is known as the P-P interval. In most people, there is a slight variation of less than 0.16 seconds. In cases of respiratory sinus arrhythmia, the P-P interval will often be longer than 0.16 seconds when the person breathes out.

As the heart speeds up, during exercise, for example, the heart rate rhythm tends to become more regular.



An electrocardiogram (ECG) may be used to diagnose arrhythmia. It is a reading of heart rate and rhythm.
An electrocardiogram (ECG) may be used to diagnose arrhythmia. It is a reading of heart

The most common way to diagnose arrhythmia is by taking an electrical recording of the heart rhythm, using a machine called an electrocardiogram (ECG or EKG).

An ECG or EKG measures several different aspects of the heart, including the rate, rhythm, and intervals between beats.

In cases of respiratory sinus arrhythmia, the heart rate per minute is usually normal. However, the time between each beat may vary, indicating an arrhythmia.

The time between each beat will be shorter as a person inhales and longer as they exhale.

Often there is a variation of more than 0.12 seconds between the longest interval and the shortest interval. This will give the doctor the clearest sign that the person has sinus arrhythmia.


Causes and risk factors

Sinus arrhythmias are common in children and are sometimes found in adults as well. Children who have respiratory sinus arrhythmia will tend to see their symptoms decrease, as they get older without the need for treatment.

While the exact cause of respiratory sinus arrhythmia is not known, researchers believe it may occur to increase efficiency or allow the heart to do less work while maintaining the correct levels of blood gases.

One potential cause of arrhythmia is exercising to excess.
One potential cause of arrhythmia is exercising to excess.


Other irregular rhythms of the heart

There are many types of arrhythmia that originate in other electrical pathways of the heart. The main types include:

  • Atrial fibrillation: The heart beats irregularly due to conduction abnormalities.
  • Supraventricular tachycardia: The heart rate is abnormally fast when at rest.
  • Heart block: When the heart beats more slowly, which may cause a person to collapse.
  • Ventricular fibrillation: The heart has a disorganized rhythm that leads to loss of consciousness and death if not treated.

Arrhythmias can affect people of any age, although atrial fibrillation is more common in older people.

Factors that increase the risk of arrhythmia include:

  • drinking alcohol
  • tobacco use
  • excessive exercise
  • caffeine consumption
  • certain medications and recreational drugs
  • being overweight
  • having a viral illness
  • previous heart attack or heart failure

Sick sinus syndrome

Sick sinus syndrome (SSS) is when the sinus node causes abnormalities in the heart rhythm. This occurs when the sinus node scars and is replaced by fibrous tissues over time.

There are several arrhythmias associated with SSS:

  • atrial fibrillation
  • severe sinus bradycardia
  • tachycardic-bradycardic syndrome, also known as tachy-brady syndrome
  • sinus exit block or sinus pauses

SSS more commonly affects older people and both sexes equally. While SSS may be asymptomatic in some cases, it can also cause a person to experience:

  • fainting
  • heart palpitations
  • fatigue
  • shortness of breath

Treatment often includes the use of a pacemaker. If left untreated, SSS can have serious consequences for a person’s health.

Medications, such as digoxin, beta-blockers, and calcium channel blocker can make SSS worse.



Respiratory sinus arrhythmia is not considered a major health concern. However, other arrhythmias can sometimes indicate heart disease.

An older person with a severe arrhythmia may require a pacemaker. People with sleep apnea are also more likely to experience arrhythmias, including respiratory sinus arrhythmia.

Cases of respiratory sinus arrhythmia in children and young people will often improve without treatment, as someone ages. This is because a child’s heart is still growing and developing and changes to the heart can lead to respiratory sinus arrhythmia.

If a child has a respiratory sinus arrhythmia, a doctor may wish to monitor it but will probably not offer any treatment unless the problem becomes severe, causes symptoms, or continues into adolescence.

However, cases in older people are more unusual and may require further examination. If respiratory sinus arrhythmia is caused by an underlying heart disease, then that will need to be treated separately.


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