A sinus arrhythmia refers to a problem with the sinus node of the heart. This controls the rhythm of the heart and can be fast (sinus tachycardia) or slow (sinus bradycardia).

This article looks at what sinus arrhythmia is, how doctors diagnose it, and whether it is a health concern. Although this article will cover different types of sinus arrhythmia, it will focus on respiratory sinus arrhythmia.

Woman holding up to halves of a model of the human heart in front of her chest.

Sinus arrhythmia relates not to the sinus cavities in the face but to the sinoatrial or sinus node in the heart. The sinoatrial or sinus node is in the upper chamber on the right side of the heart, which is the right atrium.

The sinus node is the heart’s natural “pacemaker,” which means it is responsible for setting the rhythm of a person’s heartbeats.

Normal sinus rhythm is a regular rhythm that occurs in generally healthy people. Sinus arrhythmia is an irregularity in the heart rhythm that originates at the sinus node.

In general, sinus arrhythmias can be:

  • Sinus tachycardia: a faster heart rate, beating faster than 100 beats per minute (bpm)
  • Sinus bradycardia: a slower heart rate, beating slower than 60 bpm

This section looks at the different types of sinus arrhythmia.

Respiratory sinus arrhythmia

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

The time between heartbeats is 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 0.12 seconds when the person breathes out.

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

Nonrespiratory sinus arrhythmia

Nonrespiratory sinus arrhythmia (NRSA) more commonly occurs in adults.

Electrocardiogram (ECG) results for NRSA can be similar to those for respiratory sinus arrhythmia. However, the difference is that NRSA does not affect a person’s breathing.

Although it can occur in otherwise healthy individuals, NRSA is more likely to occur in those who have heart disease or who have taken excess digoxin.

Ventriculophasic sinus arrhythmia

Ventriculophasic sinus arrhythmia occurs mostly in patients with third-degree heart block, also called an AV block. This is when the electrical rhythms of the heart are disrupted or blocked, causing the heart to beat slowly.

Third-degree heart block can be fatal if a person does not receive treatment. It can cause heart failure or loss of consciousness.

Symptoms of a third-degree heart block include chest pain, fatigue, and shortness of breath.

The most common way to diagnose arrhythmia is by taking an electrical recording of the heart rhythm using an ECG machine.

An ECG measures several 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 beats may vary, indicating an arrhythmia.

The time between beats 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.

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, some say that it arises from the stimulation of the vagus nerve and changes in cardiac filling pressures during respiration.

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 as a result of conduction abnormalities.
  • Supraventricular tachycardia: The heart rate is abnormally fast when at rest.
  • Heart block: The heart beats more slowly. This may cause a person to collapse.
  • Ventricular fibrillation: The heart has a disorganized rhythm. This can lead to loss of consciousness and death if a person does not receive treatment.

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

Factors that increase the risk of arrhythmia include:

  • alcohol consumption
  • tobacco use
  • excessive exercise
  • caffeine consumption
  • certain medications and recreational drugs
  • high body weight
  • 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 fibrous tissues replace it 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. It affects males and females equally. While SSS may be asymptomatic in some cases, it can also cause a person to experience:

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 blockers can make SSS worse.

Respiratory sinus arrhythmia may be hard to prevent, as it is commonly seen in young, otherwise healthy people.

It tends to decrease as people age, especially in people living with diabetes or heart failure. Generally, making an effort to maintain a healthy heart is helpful for people.

Some best practices for heart health:

Healthcare professionals do not generally consider respiratory sinus arrhythmia a major health concern. However, other arrhythmias can sometimes indicate heart disease.

An older person with 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 the people age. This is because a child’s heart is still growing, 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 may 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 underlying heart disease is causing respiratory sinus arrhythmia, a healthcare professional will need to treat the heart disease separately.

Sinus arrhythmia is an irregularity of the heartbeat.

Sinus arrhythmia in young people is usually not a cause for concern. In most cases, a doctor will not offer treatment and will instead choose to monitor the person’s heart rate over time. Sinus arrhythmia tends to decrease as a person gets older.

Although the arrhythmia is not harmful, older people should consult a healthcare professional to find out the cause and to receive any necessary treatments. This is because underlying conditions such as heart diseases and diabetes can aggravate the arrhythmia.