Matters of the Heart - Sinus Rhythms
Matters of the Heart: Sinus Rhythms
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 ECGs.
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
(Photo courtesy of practicalclinicalskills.com)
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 to life. Thus, efforts are exerted to maintain this rhythm or return patients to this rhythm.
How to get to 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 of the problem itself. Here’s a quick list of common medications and procedures used to restore the heart’s normal rhythm.
Beta Blockers (link to post)
Ace Inhibitors (link post)
Antidysrhythmics: Classes I-IV (e.g. Amiodarone -Class III and Lidocaine-Class Ib, and Adenosine)
Cardiac Catheter Ablation
Cardioversion: Shocking the heart
Vagal Maneuvers (should I write a post on these too?)
What about those 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):
What is Sinus Bradycardia? 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?
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 heart failure, heart blocks, polypharmacy, Myocardial Infarction (MI) cardiomyopathy.
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.
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 indicated 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, and changes in levels of consciousness.
Assess blood pressure, using at least 2 different methods, to verify a low blood pressures. Methods such as appropriately functioning arterial line, automatic blood pressure cuff, and manual blood pressure cuff.
Primary drugs for treatment (If unstable or if a patient becomes symptomatic with their bradycardia, the following are drugs that you may see):
Other treatments include:
Temporary or permanent pacemakers
Coughing (can help increase HR)
Increasing physical activity
Sinus Tachycardia (ST):
What is sinus tachycardia? 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?(source)
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 it happen?
Tachycardia is one of those Rhythms that can come from a lot of different origins. Tachycardia can be the result of:
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, palpitations, and 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 patients 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 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.
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 run down of 12 lead EKG interpretation. It has always helped me have a reference point to rule out and compare/contrast my 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 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.
PracticalClinicalSkills.com : EKG. (n.d.). Retrieved from https://www.practicalclinicalskills.com/ekg
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.