What are Premature Atrial Contractions (PAC)?

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.

Simply put, a PAC is when the atria contracts before it is supposed to.  

Obviously… DUH.



But why or how does this happen?

Let’s go back to Normal Sinus Rhythm where we learned about the sinoatrial node (SA node). This node, located in the right atrium, is the pacemaker of the heart keeping the heart beating at about 60-100 beats per minute. A PAC occurs when an impulse is generated in the atria from somewhere other than the SA node creating a heartbeat… you know… prematurely.

What are the signs and symptoms of a Premature Atrial Contraction?

Patients may not even know they are having PACs and usually do not have any signs or symptoms. However, the patient may feel like their heart is “skipping a beat” or “fluttering.”

What do Premature Atrial Contractions look like?

Since a patient probably won’t know they are having a PAC, they will likely be found when performing an EKG/ECG.

Note the abnormally shaped P wave and irregularity of the R-R measurements.

Sometimes the beat can occur early enough that the ventricles do not respond thus the EKG/ECG just has an additional P wave.

Not every EKG/ECG looks the same so you will need to know what to look for and any variants. Some of the things to look for when reading an EKG/ECG with PACs on it include the following:


  • Sinus Pause
    • Look for the T wave to be distorted
    • Happens when the additional impulse arrives to the Atrioventricular Node (AV node) during an absolute refractory period.
  • Peaked or camel hump looking waves
    • P waves can be hidden in T waves
    • Sometimes this makes the PAC look like a Premature Junctional Contraction (PJC)
  • Inverted P wave with a short P-R interval
    • This occurs when the additional impulse is low in the atria
  • Blocked PAC
    • This occurs when the atria create an impulse that does not complete its journey to the ventricles. Thus no QRS complex following the P wave


There are two types of PACs.

  • Unifocal– Comes from one source
    • PACs will look the same
  • Multifocal– Comes from multiple sources
    • PACs will vary in how they look

When charting that an EKG/ECG has a PACs, you will chart their frequency. If they occur in a pattern of beats then you will chart how many beats there are starting with the PAC. So if every other beat (or every two beats) is a PAC then the patient is having Bigeminal PACs. If the patient is having PACs every three beats then it is Trigeminal PACs and so on.

If a patient has more than one PAC in a row you will also chart this. Two PACs in a row is called a couplet, three in a row is called a triplet, etc.

You will want to report off these EKG/ECG findings to the next nurse taking care of the patient so don’t forget to write this down in your report sheet!

What are the nursing interventions and considerations for Premature Atrial Contractions?

Although PACs are generally harmless, they can sometimes be problematic. As a nurse, you should be looking for an underlying cause. There isn’t always a specific cause, however, in the case there is a specific cause, you will want to address it to fix the arrhythmia and prevent other potential issues in the future.

Potential causes of Premature Atrial Contractions include the following:

  • Valvular malfunction
    • The hearts tricuspid and mitral valve could be malfunctioning thus causing the atria to fire improperly.
  • Hypertension
  • Anxiety/Stress
  • Caffeine
  • Alcohol
  • Infection
  • Hypoxia
  • Digoxin Toxicity
  • Electrolyte imbalance
    • Hypokalemia
    • Hypomagnesemia
  • Sympathomimetics
  • Beta Agonists

As mentioned earlier, it’s is prudent to be aware that PACs can sometimes lead to or cause other arrhythmias, such as atrial flutter (Aflutter) or atrial fibrillation (Afib). That means that if your patient is experiencing frequent PACs, or has a history of arrhythmias, they will likely need to be on a cardiac or telemetry monitor.

For example, a patient is complaining of chest pain, the EKG/ECG comes back Normal Sinus Rhythm with unifocal occasional PACs, and the patient gets lab work done. If the lab work comes back and the patient has a high white blood cell count you may want to throw that patient on the cardiac monitor to watch their rhythm. Having an infection might be the underlying cause OR it could be a complicating factor that could turn the rhythm into Atrial Flutter.

The lesson here is to be safe, not sorry. That is why you should be ready on the floor with your ECG pocket guide.

How do you Treat Premature Atrial Contractions?

Unless the patient is symptomatic, you do not treat PACs. However, in the event that they ARE symptomatic, the focus will be on discovering the underlying cause and then getting rid of it.



If an underlying cause can’t be found or if it is benign in nature, the patient could potentially take an antiarrhythmic, but this would be dependant on the patient and the provider. The patient may also wear a holter monitor to further investigate the PACs.

You will teach the patient to monitor themselves for feelings of a skipped heartbeat or a fluttering heart and to seek medical help if they notice any signs or symptoms that are out of the ordinary for them.


Written by ME! Susan DuPont of BossRN is a full-time bedside emergency room nurse in a level one trauma center. In her spare time, she likes to fish, hunt, and travel.

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