Matters of the Heart: Sinus Rhythms

Disclaimer: This material should be used to supplement your understanding of the cardiovascular system. Any use of the information given in this post series is at your own risk and should be verified prior to making it a part of your nursing practice. There may be affiliate links associated with some products but we promise that we will never recommend anything that we don’t use ourselves.

Today we are taking it back to the basics.

I mean the bare bones of ECG interpretation.

Sinus Rhythms.

The big star of the “Sinus Rhythm Family” is Normal Sinus Rhythm (NSR).

Do you remember that age-old adage that “If you at least know what normal is, then you can tell when something is abnormal and get help.”?

I personally believe that adage is 100% spot-on. Recognizing what a normal heart rhythm looks like can be a critical foundational block when it comes to interpreting ECG/EKGs.

So, as always, we are going to keep things sweet and simple.

What is Normal Sinus Rhythm (NSR)?

Essentially NSR is the basic appropriate rhythm of a properly functioning heart, with heart rates between 60 bpm-100 bpm (this range may differ by a couple of numbers according to what resource you’re using and the age of the patient). It is called “Sinus” rhythm because the impulses for this rhythm originate in the sinoatrial node (a.k.a the pacemaker of the heart) and continue down through the regular pathway (SA node to AV node to the Bundle of His to the Purkinje fibers).

NSR is the standard to which all other heart rhythms are judged and compared.

What does Normal Sinus Rhythm look like?



Normal Sinus Rhythm (NSR) example

Normal Sinus Rhythm

(Photo courtesy of

  • The atrial and ventricular rate and rhythm are regular in spacing and pattern.
  • The rate is between 60 bpm and 100 bpm
  • There is one P-wave before every QRS complex.
  • The p-wave should be pointing with the hump going up.
  • P-waves should be similar in appearance and spacing.

What’s the big deal with Normal Sinus Rhythm?

Well, nothing really. NSR is the goal for all patients. It is the rhythm most compatible with life. Thus, efforts are exerted to maintain this rhythm or return patients to this rhythm.



What can we do about Normal Sinus Rhythm?

Achieving NSR is a complex orchestra of electrical signals, chemical reactions, and pressure changes. Things that can help a body experiencing anything other than normal sinus rhythm are numerous and dependent on the problem itself. Here’s a quick list of common medications and procedures used to restore the heart’s normal rhythm.

  • Pharmacological:
    • Beta Blockers 
    • Ace Inhibitors 
    • Antidysrhythmics: Classes I-IV (e.g. Amiodarone -Class III and Lidocaine-Class Ib, and Adenosine)
  • Procedural:
    • MAZE Procedure
    • Cardiac Catheter Ablation
    • Cardioversion: Shocking the heart
    • Vagal Maneuvers 

What about other sinus rhythms?

Don’t worry, we are going to briefly talk about them next! There are 2 other key members to the Sinus Rhythm “family.”

  • Sinus Bradycardia (SB):
    • Definition: A slow, yet regular, rhythm which beats at a rate less than 60 beats per minute. Remember, it is called sinus because the electrical impulses are derived from the primary pacemaker of the heart, the sinus node.

What does sinus bradycardia look like?

Sinus Brady(Source)

Note: We can still see the p-waves! The PR interval is still within normal ranges less than .20. Increased PR intervals could indicate an AV-block.

Why does Sinus Bradycardia happen?

  • Bradycardia can happen for many reasons, as you’ve probably guessed. Some of the major causes can include:

What’s important to know about sinus bradycardia?

If not on the extreme end (less than 45 or so) it can be a rhythm that is stable and expected in younger patients and individuals that lead active lifestyles and are “in-shape.”

Some patients may naturally become more bradycardic during sleep, always assess the whole patient and don’t freak out until you have to.

Sinus Bradycardia (SB) becomes problematic when the rate, stroke volume, and/or cardiac output are insufficient to perfuse the organs.

  • Always assess your patients regularly, for signs and symptoms that indicate their condition is decompensating or worsening.
    • Poor perfusion can manifest in multiple ways:
      • Cyanosis
      • Drop in urine output (body sacrifices the kidneys before the vital organs)
      • Dizziness/weakness,
      • Chest pain
      • Changes in Levels of Consciousness (LOC)
    • Assess blood pressure, using at least 2 different methods, to verify low blood pressure. Methods such as: appropriately functioning arterial line, automatic blood pressure cuff, and manual blood pressure cuff.

Primary drugs for the treatment of Bradycardia

If unstable or if a patient becomes symptomatic with their bradycardia, the following are drugs that you may see:

  • Atropine (ACLS)
  • Epinephrine (ACLS)
  • Dopamine
  • Other treatments include:
    • Temporary or permanent pacemakers
    • Coughing (can help increase HR)
    • Increasing physical activity
  • Sinus Tachycardia (ST):
    • Definition: A regular, but rapid, rhythm with impulse initiation from the SA node and a rate above 100 beats per minute that rarely exceeds 150 beats per minute (which is a whole other issue).

What does sinus tachycardia look like?

Sinus Tachycardia


Note: Notice that p-waves are still visible and that the rate and rhythm is consistent. The QRS is still narrow. Widened QRS complexes and increased rates can lead to wide-complex v-tach, which is a more serious arrhythmia.

Why does Sinus Tachycardia happen?

  • Tachycardia is one of those Rhythms that can come from a lot of different origins. Tachycardia can be the result of:
    • Physical exertion
    • Anxiety
    • Pain
    • Pulmonary embolisms
    • Fever/infection
    • Poor perfusion/oxygenation
    • Intake of:
      • Caffeine
      • Pharmaceutical drugs
      • Recreational drugs

What’s important to know about sinus tachycardia?

Like sinus bradycardia, sinus tachycardia can be less serious and non-life threatening if it is controlled and adequate perfusion is taking place.

Tachycardia can cause symptoms such as:

  • Hypotension
  • Dizziness
  • Chest pain 
  • Shortness of Breath (SOB)
  • Palpitations
  • Heart Failure

It’s important to assess the cause of tachycardia. Ask yourself questions like:

  • Does the tachycardia only happen when the patient moves or is walking?
  • Does it happen when they turn themselves in the bed?
  • How long does it take for the patient’s rate to slow when they are still?
  • Does it happen when they are sitting still or sleeping?

Assessing the trend of tachycardia is also important. Know if a patient’s rate has been trending up and if they become symptomatic.

Primary drugs and treatments: Beta-Blockers (drugs that end in -lol) and calcium channel blockers are two of the primary medications you may see in the treatment of tachycardia. Many times, if stable, some providers may choose to hold off on pharmacological treatment until it is warranted. For anxiety-induced tachycardia, removing the stressor and remaining calm helps.

Sustained rates above 120 beats per minute should especially be monitored and reported to a physician or advanced practice provider.

Nursing Tidbits:

  • Remember that if you can learn to recognize NSR, you will be able to identify when the heart rhythm is altered or abnormal and bring it to the attention of another, more experienced, nurse, physician, or advanced practice provider.
  • I still keep a small badge card on my badge that gives a rundown of 12 lead EKG/ECG interpretation. It has always helped me have a reference point to rule out and compare/contrast my EKG/ECG measurements and interpretations. Check out my must-have badge goodies and gadgets post! Below are 2 EKG Badge cards I suggest.
  • Always partner ECG/EKG interpretation with vital signs and physical assessment.
  • If NSR can’t be achieved, then keeping a patient as close to this rhythm as possible, such as a controlled sinus tachycardia or sinus bradycardia, should be the goal.



Coviello, J. S. (2017). ECG interpretation made incredibly easy!: Pocket guide (3rd ed.). Philadelphia: Wolters Kluwer.

Terry, C. L., & Weaver, A. L. (2011). Critical care nursing demystified. New York: McGraw Hill Medical. : EKG. (n.d.). Retrieved from

Written by:

IMG_2861 (1)

Patrick McMurray of PatMacRN is a full-time critical and intermediate care nurse at Level I academic trauma center. In his spare time, Patrick enjoys reading, traveling, and improving his French language skills.


Join the BossRN Family

Subscribe to become part of the family. Get information on great deals, free information, and invites to cool events.

Unsubscribe at any time. Powered by ConvertKit
%d bloggers like this: