03.02 Sinus Bradycardia

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Overview of Sinus Bradycardia

  1. Characteristics of sinus bradycardia
    1. SA node  initiates electrical conduction
      1. Same as normal sinus rhythm but HR <60
    2. Rhythm
      1. Regular
    3. Heart rate
      1. <60
    4. P:QRS ratio
      1. 1:1
    5. PR Interval
      1. 0.12-.20 seconds
    6. QRS complex
      1. 0.06-0.12 seconds

Nursing Points for Sinus Bradycardia


  1. Patient Presentation
    1. Asymptomatic
    2. Symptomatic
      1. Syncope
        1. Lightheaded
        2. Vertigo
      2. Decreased cardiac output
        1. Fatigue
        2. Short of breath
        3. Chest pain
        4. Hypotensive
  2. Causes
    1. Medications
      1. Digoxin Toxicity
      2. Beta Blockers
      3. Calcium Channel Blockers
    2. Athletes
    3. Vagus nerve stimulation
    4. SA node malfunction
    5. Hyperkalemia
  3. Nursing Interventions
    1. Determine if  symptomatic or asymptomatic
    2. Determine the cause of bradycardia

Assessment of Sinus Bradycardia

  1. Apical heart rate
    1. Stable
    2. Unstable
  2. Vertigo/syncope
  3. Hypotension
  4. Chest pain/SOB
  5. Electrolytes

Therapeutic Management for Sinus Bradycardia

  1. Find and treat the cause
  2. Asymptomatic
    1. Continue to monitor
  3. Symptomatic
    1. Atropine
      1. Follow ACLS Guidelines
    2. Pacemaker
      1. Temporary
        1. Transcutaneous
        2. Transvenous
      2. Permanent

Nursing Concepts

  1. EKG Rhythms
  2. Perfusion

Patient Education

  1. Check and count own radial pulse
    1. Report if abnormally low
  2. If hypotensive and dizzy
    1. Prevent falls
      1. Lay down and elevate feet


Hey guys, in this lesson we are going to talk about the characteristics of sinus bradycardia and most common symptoms, some of the possible causes, treatments and nursing interventions, and we are also going to break down each of the steps to learn how to identify it on an EKG.

So with sinus bradycardia, the SA node initiates the electrical conduction just like in normal sinus rhythm, the only difference is that it is signaling at a rate of less than 60 beats per minute. Since the SA node is still initiating the conduction, it is called sinus bradycardia. So let’s use the 6 step method to identify the characteristics of sinus bradycardia and identify rhythm on an EKG. If you have not listened to the normal sinus rhythm lesson, please make sure you go and check that out because it breaks down the 6 steps in detail so it helps you understand it and apply them to other lessons with abnormal rhythms. So let’s get started and identify our rhythm, our first step and look to see if the rhythm is regular or irregular, we need to count the small boxes from this R wave to this R wave and we have about 29, there is 29 from here to here so we have the same number of boxes so we have a regular rhythm. In step number 2 we need to identify the heart rate, so we determine if it’s a six second strip, the easiest way to do this is to count the large boxes from the beginning of the strip to the end, if you have large 30 boxes that means you have a 6 second strip. So we count the R waves and multiply by 10 and get 50 beats per minute. We need to do this with the 1500 method and that would be 1500 divided by 29 and that gives us 51 beats per minute this method is more accurate and it helps when we have an abnormal rhythm. Now our heart rate would be between 50-51 beats per minute. Step number 3 we need to look at the P to QRS ratio do we have 1 P wave followed by 1 QRS, so if we look at our strip, we do. We have one P wave followed by a QRS, P to QRS ratio is 1 to 1. Step number 4 would be our PR interval. We would start with the beginning of the P wave to the beginning of the Q wave and we get 5 small boxes or 0.20 seconds which is also a normal PR parameters. In step number 5 we look at our QRS complex, we measure from the beginning of the Q wave to the end of the S wave and we get 2 small boxes or 0.08 seconds and that is also within the normal parameters. So step 6 would be to identify the rhythm and we have sinus bradycardia. So let’s recap and break it down and look at the characteristics of sinus bradycardia. Our rhythm is regular, our heart rate is 50-51 beats per minute our P to QRS ratio is 1 to 1 our PR interval in normal and our QRS complex is normal so that gives us sinus bradycardia. Because this is not a normal rhythm it our job as nurses to figure out why our patients are bradycardic and what is going on.

Ok so when you have a patient with bradycardia the most important thing you can do initially is assess your patient and determine if they are asymptomatic or symptomatic because that determines how we treat them. If they are symptomatic they usually present with syncope, they will complain of feeling lightheaded and dizzy. This causes a decreased cardiac output they have fatigue shortness of breath and chest pain and hypotensive. So the heart pumps blood to the brain, the lungs, the body and the heart itself, when the heart is beating at a rate of 40 beats per minute it’s not contracting at often as it should so it is sending less blood to the organs that need it. This decreases cardiac output and people complain of fatigued, short of breath, chest pain and lightheadedness. Now that you have determined the signs and symptoms, you have to find out the cause, why are they bradycardic. If you can find out the cause, it’s easier to treat them. The common causes are medications like beta blockers, calcium channel blockers these are the most common ones. Another major cause is patients that are taking digoxin or digitalis, if their dig levels are toxic, they have dig toxicity. Dig slows down the heart rate and increases the force of contraction so when a patient has toxic levels of dig bradycardia increases. Another common cause is stimulating the vagus nerve, this usually happens when patients are bearing down to try to have a bowel movement. A couple other causes are the SA node malfunction, if the SA node stops working the heart is not contracting like it should and heart rate will go down. And in hyperkalemia, high levels of potassium can affect depolarization and that will slow down the heart rate. So now let’s talk about treating bradycardic patients.

So the therapeutic management for bradycardic patients is to determine the cause. If you can find out why they are bradycardic you know how to treat and what to treat and bradycardia will improve.
Next, if your patient is asymptomatic and they have a heart rate in 50s continue to monitor them if they are asymptomatic, if they do become symptomatic we much follow the ACLS guidelines. So we will give them some atropine and start with 0.5mg and increase the heart rate if it does not work, we give them another 0.5mg of atropine and hope the heart rate goes up. If it doesn’t, we need to prepare the patient for a pacemaker. We can do 2 temporary pacemakers a transcutaneous or transvenous. So let’s talk about pacing, if I have a patient and their heart rate is in the 20s, I need to emergently pace them so I am going to do transcutaneous pacing. They will be connected to the defibrillator to the pacer mode at a heart rate of 60-80 beats per minute. It will send an electrical activity transcutaneously to the heart and the heart will start pacing. If you have a patient being transcutaneously paced, do not touch them you will get shocked. Another temporary method of pacing would be transvenous, we need venous access and a catheter is inserted with a lead directly in their heart to pace them. If the patient needs a long term treatment they will get a permanent pacemaker. Always follow ACLS guidelines to treat bradycardia.

So the key points to take away from this lesson are to remember the characteristics of sinus bradycardia are the same as normal sinus rhythm, the only abnormality is that the heart rate is less than 60 beats per minute. Always assess the patient first and find out if they are symptomatic or asymptomatic. Determine the cause if you know why they are bradycardic you know how to treat them. If they are symptomatic, give atropine or prepare for a temporary or permanent pacemaker. Follow ACLS guidelines.

I hope you guys have enjoyed this lesson and feel more comfortable being able to identify sinus bradycardia and most importantly know the nursing interventions for this abnormal rhythm. Make sure you check out all of the resources attached to this lesson to become more familiar with sinus bradycardia. Now, go out and be your best self today! And, as always, happy nursing!