What is normal sinus rhythm with sinus arrhythmia

Q: What is a sinus arrhythmia on ECG?

When there is irregularity in the sinus rate, it is termed sinus arrhythmia. A sinus rhythm faster than the normal range is called a sinus tachycardia, while a slower rate is called a sinus bradycardia.

AFib and Normal Sinus Rhythm

Your heart's job is to pump blood throughout your body. When it's working the way it should, it pumps to a regular, steady beat. This is called a normal sinus rhythm. When it's not, you could have an irregular heartbeat called AFib.

Table of Contents Show

AFib and Normal Sinus Rhythm
What Happens With a Normal Sinus Rhythm?
What Does AFib Feel Like?
Normal Sinus Rhythm
Sinus Rhythm vs. Heart Rate
Sinus Bradycardia
Symptoms
Sinus Tachycardia
Symptoms
A Word From Verywell
Frequently Asked Questions
What is a sinus arrhythmia on ECG?
What is a healthy sinus rhythm?

You probably don't think much about your heartbeat because it happens so easily. It's really like a complex dance. During each beat, the two upper chambers of your heart squeeze, or contract. Those are the atria. Then the two lower chambers, called the ventricles, contract.

When the chambers contract, they move the blood along. Your heart's electrical system controls the timing of the pumping.

What Happens With a Normal Sinus Rhythm?

Each heartbeat starts with a signal from the sinoatrial (SA) node, in your right atrium. The SA node is called the heart's pacemaker because it adjusts your heart rate based on what you're doing. It raises your heart rate (the same thing as your pulse) when you exercise and slows it down when you sleep.

The signal spreads across the right and left atria. That makes them contract and forces blood into your ventricles. Then, the signal moves to the atrioventricular node (AV) node, which is near the middle of your heart.

From there, the signal travels through the ventricle walls. That makes them contract and squeeze blood out of the heart. The right ventricle sends blood to your lungs, while the left pumps it to the rest of your body. The walls then relax and wait for the next signal.

When everything is working smoothly, you have a normal sinus rhythm and your heart beats between 60 and 100 times per minute.

Sometimes the heart's electrical system doesn't work the way it should. Atrial fibrillation, also called AF or AFib, is the most common type of irregular heartbeat.

In this case, the signals get jumbled. As a result, instead of beating strongly and regularly, the atria quiver. So blood doesn't move into the ventricles very well.

Instead of the dance being nice and organized, things are hectic and confusing. Many signals -- sometimes as many as 600 -- leave the atria at the same time, competing to get through the AV node to the ventricles. However, the AV node prevents them all from getting through. Only about one or two out of every five signals pass through.

They go quickly and messily, resulting in an irregular heartbeat. The heart rate during AFib often varies between slow, normal, or fast.

What Does AFib Feel Like?

Some people have no symptoms. If you have them, you might feel:

Fast, irregular heartbeat
Fluttering, thumping, or flip-flopping in your chest
Shortness of breath
Dizziness
Lack of energy when you exercise
Weakness
Fatigue
Lightheadedness
Confusion
Chest pain

Some people have AFib every once in a while. Symptoms might last for a few minutes or a few hours. Then things return to normal.

Other people have AFib often and need treatment to get their heartbeat to return to a normal sinus rhythm.

Call your doctor if you have symptoms. AFib won’t cause a heart attack in a healthy heart, but it does raise your odds of having a stroke. And timely treatment, usually with a medication called a blood thinner (your doctor may call it an anticoagulant), can prevent strokes.

Normal sinus rhythm (NSR) is another name for a normal heart rhythm. The heartbeat is controlled by electrical signals, called impulses, that arise from a structure in the heart called the sinus node. These signals are transmitted in a controlled way to the four chambers of the heart, causing them to contract and relax in sequence to pump blood in and out of the heart.

However, the sinus rhythm can sometimes become irregular, referred to as sinus arrhythmia. There are several types of arrhythmia that originate from the sinus node, some of which cause the heart to beat too slowly or too rapidly.

This article explains how the sinus rhythm regulates heartbeats. It also discusses how different arrhythmias occur, including their various causes and symptoms.

Ed Reschke / Getty Images

Normal Sinus Rhythm

The heart's rhythm is referred to as sinus rhythm because the electrical impulses are generated by the sinus node.

These impulses are what you see as up-and-down patterns of an electrocardiogram (ECG). With a normal sinus rhythm (NSR), the pattern will be uniform with high and low impulses falling within "normal" parameters.

The pattern of electrical impulses reflects the way that the chambers normally beat to allow blood in and out of the heart. There are two sets of heart chambers:

Atrium: These are the upper chambers that receive blood from the body.
Ventricles: These are the lower chambers that pump blood out of the heart and back into circulation.

The sinus node consists of a group of cells called pacemaker cells that are clustered in the right atrium of the heart. These cells produce electrical impulses that cause heart chambers to contract and relax in order so that blood can move through the heart as follows:

Blood enters the right atrium and passes into the right ventricle.
The right ventricle pumps blood to the lungs where it becomes oxygenated.
The oxygenated blood is brought back to the heart by the pulmonary veins and passes into the left atrium.
Blood passes into the left ventricle and is pumped out to the body.

A normal sinus rhythm is one in which the rate of firing is regular and neither too slow nor too quick.

Sinus Rhythm vs. Heart Rate

Sinus rhythm is the pattern of your heartbeat. Heart rate is how many times the heart beats per minute. A normal sinus rhythm is associated with a heart rate between 60 and 100 beats per minute.

Sinus Bradycardia

There are a number of circumstances in which it is normal for the sinus rhythm to be at the low end of the range of beats per minute. A slow heart rate is referred to as bradycardia.

Causes

Sinus bradycardia can occur normally during sleep, when most people experience a dip in heart rate to below 60 beats per minute. Trained athletes can have resting heart rates in the 40s even while awake.

Bradycardia may also be related to health problems that directly or indirectly affect the normal sinus rhythm. These include:

Congenital heart disease (a heart defect present at birth)
Heart damage caused by heart disease or heart attack
Aging-related heart deterioration
Obstructive sleep apnea (gaps in breathing during sleep)
Myocarditis (heart inflammation)
Hypothyroidism (low thyroid function)
A complication of heart surgery
Electrolyte imbalances, such as calcium and potassium
Certain medications, like sedatives and opioids

Symptoms

A slow heart rhythm without symptoms is usually no cause for concern. However, when the heartbeat becomes too slow to pump enough blood throughout the body, treatment may be needed. This may include the use of a pacemaker.

When a person's heart rate is too slow while they're awake, they may have a disorder called sinus node disease or sick sinus syndrome. Symptoms include:

Chest pain
Severe fatigue
Lightheadedness or dizziness
Shortness of breath
Confusion
Fainting

Sinus Tachycardia

Sinus rhythm that is abnormally fast is referred to as sinus tachycardia. It can be normal for the heart rate to speed up during exercise to ensure there is extra blood to fuel the activity.

Causes

Sinus tachycardia also can occur in people for any number of health reasons, including:

Fever
Hypertension (high blood pressure)
Hypotension (low blood pressure)
Hyperthyroidism (overactive thyroid)
Anemia (low red blood cells or hemoglobin)
Electrolyte imbalances, like sodium and magnesium
Heavy caffeine use
Heavy alcohol use
Certain medications, including some antidepressants and antibiotics
Smoking
Illegal drugs, like cocaine or methamphetamine

Some people have tachycardia for no apparent cause, referred to as inappropriate sinus tachycardia (IST). A similar condition called postural orthostatic tachycardia syndrome (POTS) occurs when a person stands upright, causing tachycardia without a drop in blood pressure.

Symptoms

Tachycardia may not cause recognizable symptoms in some people. When it does, symptoms may include:

Rapid pulse
A pounding heartbeat
Palpitations (heart flutters or skipped beats)
Chest pain
Shortness of breath
Dizziness or lightheadedness
Fainting

Summary

A sinus rhythm is the beating of the heart caused by electrical impulses from the sinus node. The sinus node is a group of cells in the heart that generates these impulses, causing the heart chambers to contract and relax to move blood through the body.

A normal heartbeat is referred to as normal sinus rhythm (NSR). An abnormally slow heartbeat is called bradycardia, while an abnormally fast heartbeat is called tachycardia.

A Word From Verywell

Abnormally slow or abnormally fast heartbeats should never be ignored, especially if they occur for no known reason or are causing symptoms. The cause may end up being nothing serious, but it can also be a sign of an undiagnosed medical condition.

Speak with your healthcare provider who may refer you to a heart specialist known as a cardiologist. The cardiologist can perform an ECG and other tests used to measure the electrical activity or function of the heart muscle.

These tests can pinpoint the underlying cause of your condtion and ensure that you receive the appropriate treatment.

Frequently Asked Questions

Is sinus arrhythmia serious?
Sinus arrhythmia can be normal, especially in young and healthy people. But some, like those that produce shortness of breath or dizziness, may point to serious conditions.
Can anxiety cause sinus arrhythmias?
Yes, anxiety is one possible cause. Some people who experience anxiety-related sinus arrhythmias may benefit from meditation, yoga breathing, and similar practices.
What should a sinus rhythm look like?
An electrocardiogram (ECG) can show the regular, organized electrical activity of your heartbeats. This includes a small impulse from the sinus node, followed by the spike that reflects the heartbeat itself, and then a return state before the next beat.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

American Heart Association. About Arrhythmia.
Davidovic G, Iric-cupic V, Milanov S, et al. When heart goes "BOOM" to fast. Heart rate greater than 80 as mortality predictor in acute myocardial infarction. Am J Cardiovasc Dis. 2013;3(3):120-8.
American Heart Association. Bradycardia: slow heart rate.
Choudhury M, Boyett MR, Morris GM. Biology of the sinus node and its disease. Arrhythm Electrophysiol Rev. 2015;4(1):28-34. doi:10.15420/aer.2015.4.1.28
Bibas L, Levi M, Essebag V. Diagnosis and management of supraventricular tachycardias. CMAJ. 2016;188(17-18):e466-73. doi:10.1503/cmaj.160079
Wettersten N, Fan D, Hsia HH. Not simply sinus tachycardia. The American Journal of Medicine. 2015;128(9):e13-e14. doi:10.1016/j.amjmed.2015.04.024
Page RL, Joglar JA, Caldwell MA, et al. 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia. Heart Rhythm. 2016;13(4):e136-e221. doi:10.1016/j.hrthm.2015.09.019
Mortola JP, Marghescu D, Siegrist-Johnstone R. Respiratory sinus arrhythmia in the immediate post-exercise period: correlation with breathing-specific heart rate. Eur J Appl Physiol. 2018 Jul;118(7):1397-1406. doi:10.1007/s00421-018-3871-6
Lee JN, Whang MC, Kang BG. Process Design for Optimized Respiration Identification Based on Heart Rate Variability for Efficient Respiratory Sinus Arrhythmia Biofeedback. Int J Environ Res Public Health. 2022 Feb 13;19(4):2087. doi:10.3390/ijerph29042087.

By Richard N. Fogoros, MD
Richard N. Fogoros, MD, is a retired professor of medicine and board-certified in internal medicine, clinical cardiology, and clinical electrophysiology.

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What is a sinus arrhythmia on ECG?

When there is irregularity in the sinus rate, it is termed "sinus arrhythmia." A sinus rhythm faster than the normal range is called a sinus tachycardia, while a slower rate is called a sinus bradycardia.

What is a healthy sinus rhythm?

Normal sinus rhythm is defined as the rhythm of a healthy heart. It means the electrical pulse from your sinus node is being properly transmitted throughout the heart muscle. In adults, normal sinus rhythm usually accompanies a heart rate of 60 to 100 bpm.