Sinus Rhythm: What's Normal and Not

Your Heart's Rhythm and How It Affects Heart Function

Normal sinus rhythm (NSR) is another name for the normal heart rhythm. The heartbeat is controlled by regular electric signals, or impulses, that spontaneously arise in a structure called the sinus node. These signals then spread across the four heart chambers, starting at the atria and then the ventricles, to ensure the heart contracts in an orderly, sequential way.

Sometimes, however, the sinus rhythm becomes irregular. This is known as sinus arrhythmia. There are several types of these arrhythmias that originate from the sinus node.

This article explains how normal sinus rhythm works. It also discusses some of the arrhythmias that may be associated with other health conditions or lead to heart-related symptoms.

A normal sinus rhythm chart
Ed Reschke / Getty Images

Normal Sinus Rhythm

The heart's rhythm is referred to as “sinus rhythm” because the electrical impulse is generated in the sinus node. These impulses are what you and your healthcare providers can see when evaluating your sinus rhythm on an ECG, or electrocardiogram.

The impulse from the sinus node begins the sequence in which the atria beat first, ejecting blood into the ventricles, and then the ventricles contract. The right ventricle ejects blood into the lungs and the left ventricle ejects blood to the rest of the body.

A normal sinus rhythm is one in which the rate of firing is not too fast nor too slow. There are several types of sinus arrhythmias that result in a too-fast or too-slow heart rate.

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's normal for the sinus rhythm to be at the low end of the range of beats per minute or at the high end. A slow heart rate is called bradycardia.

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

Slow Sinus Arrhythmias

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. This disorder can cause them to get tired easily and experience other symptoms such as lightheadedness and fainting.

Sinus node disease often must be treated with a pacemaker.

Sinus Tachycardia

Sinus rhythm that is at the high end of the normal range is referred to as sinus tachycardia. It can be normal for the heart rate to speed up during exercise, as this allows it to pump extra blood throughout the body to fuel physical exertion.

Sinus tachycardia also can occur under circumstances that aren't normal, such as during periods of stress or extreme anxiety, or when someone has a fever.

An abnormally fast heart rate also can be a symptom of hyperthyroidism, or other medical problems that require a higher cardiac output, such as anemia.

Fast Sinus Arrhythmias

A form of sinus tachycardia called sinus re-entrant tachycardia is a rare type that comes and goes suddenly and is caused by extra electrical pathways within the sinus node. It is sometimes treated with a procedure called ablation.

Some people have sinus tachycardia without any apparent underlying cause, a condition called inappropriate sinus tachycardia (IST). A similar condition is called postural orthostatic tachycardia syndrome (POTS), in which sinus tachycardia—and a drop in blood pressure—occurs when someone is standing upright.

Both IST and POTS often produce significant palpitations, lightheadedness, and other symptoms and can be challenging diagnoses.

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 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.

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7 Sources
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