EKG Interpretation, part 11: Artificial Pacemakers, Tachycardia and Bradycardia
by Cathy Parkes July 01, 2020 Updated: April 24, 2022 7 min read
In this article, we cover artificial pacemakers, including types of pacemakers and how they look on an EKG, and their synchronicity; and bradycardia and tachycardia along with their causes, symptoms, and interventions, both pharmaceutical and electrical.
The EKG Interpretation video series follows along with our EKG Interpretation Flashcards, which are intended to help RN and PN nursing students study for nursing school exams, including the ATI, HESI, and NCLEX.
The heart is made up of natural pacemakers. But if a patient's natural pacemakers fail to maintain a sufficient cardiac output, then they may require an artificial pacemaker. When we refer to pacemakers throughout the rest of this article, we will be discussing the artificial kind!
When you are interpreting an EKG strip, it's important to remember that pacemakers emit a pacing stimuli which will show as a spike.
Types of pacemakers
Pacemakers can provide atrial pacing, ventricular pacing, or both.
When the SA node in the heart fails, the patient needs a pacemaker with atrial pacing. When a patient is getting atrial pacing, you will see a spike preceding the P wave.
If a patient has a complete AV block (e.g., a third-degree AV block), they will require a pacemaker with ventricular pacing. When a patient is getting ventricular pacing, you will see a spike prior to the QRS complex.
If a patient has SA node failure and a complete AV block, they will need atrioventricular (AV) pacing (both atrial and ventricular pacing). When a patient is getting AV pacing, you will see both of the above described spikes—one spike preceding the P wave and another spike prior to the QRS complex.
Pacemakers have different synchronicity modes that you should be aware of.
Pacemakers in asynchronous mode fire at a constant rate regardless of the heart's electrical activity. It is not in sync with (or responding to) the heart's activity. On an EKG strip from a patient with an asynchronous pacemaker, you would see pacing spikes before every P wave and every QRS complex.
Pacemakers in synchronous mode only fire when the heart's intrinsic rate falls below a certain rate. It is in sync with (responding to) the heart's activity. On an EKG strip from a patient with a synchronous pacemaker, you may see spikes in some part of the strip and not in others. When the spike does not occur, it means the heart was behaving adequately.
We have discussed bradycardia throughout the EKG series, as many arrhythmias can lead to it. We will cover bradycardia in depth here so you are familiar with the causes, symptoms, and available interventions (pharmaceutical and electrical).
Bradycardia is a heart rate under 60 beats per minute.
There are a number of causes of bradycardia, many of which we have covered in depth throughout this series. Causes of bradycardia include heart block, sick sinus syndrome, hypothyroidism, medications like digoxin, and electrolyte imbalances like hypermagnesemia.
Other causes of bradycardia can include the Valsalva maneuver, bearing down during a bowel movement, or excess vagal nerve stimulation which can occur with vomiting.
Certainly not all bradycardia is bad. Some people who are very physically fit, like athletes, may have bradycardia. This is because their intense exercise has, over time, trained their heart to become more efficient by circulating the same amount of blood with fewer contractions.
Many patients with bradycardia are asymptomatic, but some patients may experience symptoms like dizziness, syncope (fainting), hypotension, and shortness of breath.
If a patient's bradycardia is asymptomatic, they will usually not require an intervention.
A pacemaker may be needed if a patient does not have sufficient cardiac output due to bradycardia
We have discussed tachycardia throughout the EKG series, as many arrhythmias can lead to it. We will cover tachycardia in depth here so you are familiar with the causes, symptoms, and available interventions (pharmaceutical and electrical).
Tachycardia is a heart rate over 100 beats per minute.
Some patients with tachycardia may be asymptomatic. If symptoms of tachycardia do occur, they can include shortness of breath, weakness, chest pain, or palpitations.
Interventions for tachycardia usually begin with identifying the underlying cause of the tachycardia and addressing that cause. However, there are some pharmaceutical and electrical interventions that can be used for more serious tachycardia dysrhythmias.
There are five classes of antiarrhythmic medications to be familiar with as pharmaceutical interventions for tachycardia. Luckily, these are all covered in our Pharmacology series!
- Class one: sodium channel blockers (procainamide, lidocaine)
- Class two: beta-blockers (propranolol, metoprolol, atenolol)
- Class three: potassium channel blockers (amiodarone)
- Class four: calcium channel blockers (verapamil, diltiazem)
- Class five: other medications (adenosine, digoxin, magnesium sulfate)
If you need to remember these antiarrhythmic medications for Pharmacology exams or the NCLEX, check out our Pharmacology flashcards for nursing students.
There are electrical interventions for tachycardia including cardioversion and defibrillation.
For patients who have ventricular tachycardia without a pulse, the required intervention is defibrillation.
Another tachycardia dysrhythmia that requires defibrillation is ventricular fibrillation. Remember that you "defib V-fib."
Alright, this is the last video in my EKG interpretation video series. In this video, we will be talking about artificial pacemakers. In addition, we'll be talking about bradycardia as well as tachycardia, what can cause those dysrhythmias, what are the symptoms of those dysrhythmias, and what are the pharmaceutical and electrical interventions we can use to treat those dysrhythmias.
Okay, so when a patient's natural pacemakers fail to maintain a sufficient cardiac output, then they may require an [artificial] pacemaker. So pacemakers emit a pacing stimuli which shows up as a spike on the EKG strip. So pacemakers can provide atrial pacing, they can provide ventricular pacing, or they can provide both, which is called AV pacing.
When a patient is getting atrial pacing, this means that they have SA node failure. So when they're getting atrial pacing, you will see a spike that precedes the P wave, like this one right here.
With ventricular pacing, a patient would require ventricular pacing if they have a complete AV block, such as a third-degree AV block. So when they're getting ventricular pacing, you will see a spike prior to the QRS complex.
A patient will need AV pacing or both atrial and ventricular pacing if they have SA node failure as well as a complete AV block. So when a patient is getting AV pacing, you'll see a spike preceding the P wave and another spike prior to the QRS complex.
So keep in mind that there is a couple different pacemaker modes.
We can have asynchronous mode, which means the pacemaker fires at a constant rate regardless of the heart's electrical activity, which is kind of what we have going on here. We can see that there's pacing spikes before every single P wave and QRS complex.
Or we can have a synchronous mode to the pacemaker, which is where the pacemaker only fires when the heart's intrinsic rate falls below a certain rate. So you may see some strips where you see some of these spikes, but in other parts of the strip, you may not see the spikes. So that means that their pacemaker is synchronous. So it's only firing when it has to, when the heart's intrinsic rate falls below a set rate. But in some cases, their heart may be behaving adequately, and they don't require pacing for certain heartbeats. So just keep that in mind as you are looking at different strips. You may not see these spikes before every P wave or before every QRS complex. It may be that the patient has a pacemaker in synchronous mode.
Now we're going to talk about bradycardia. And the information I'm going to cover here can be found on card 41 in my deck.
So there are a number of causes of bradycardia, including heart block, sick sinus syndrome, hypothyroidism, certain medications such as digoxin, certain electrolyte imbalances such as hypermagnesemia.
Other causes include infection or cardiovascular disease as well as Valsalva maneuvers, such as bearing down when you're having a bowel movement, or excess vagal stimulation can also cause bradycardia, such as when you're gagging or vomiting.
Keep in mind that athletes very commonly have bradycardia, so a heart rate that's under 60 beats per minute, and this is a normal and expected finding in athletes.
In terms of symptoms, a lot of patients are asymptomatic, meaning they don't have symptoms with bradycardia. But some patients will have symptoms such as dizziness, syncope, hypotension, and shortness of breath.
In terms of interventions, if the patient is asymptomatic, often, interventions are not required.
However, if they have symptoms with their bradycardia, we can provide pharmaceutical interventions, such as the administration of atropine as well as epinephrine and dopamine.
And then in terms of an electrical intervention, a pacemaker may be needed if the patient isn't getting a sufficient cardiac output due to the bradycardia.
Now, let's talk about tachycardia. So the information I'm going to cover here can be found on card 42 in my deck, which is the last card.
Let's talk about some of the causes of tachycardia. Causes can include physical activity, anxiety, pain, certain medications, fever, hyperthyroidism as well as anemia, and also, it could be your body's way of compensating for hypotension.
In terms of symptoms, some patients may be asymptomatic, however, symptoms can include shortness of breath, weakness, chest pain as well as palpitations.
In terms of interventions, interventions are usually first focused on identifying the underlying cause of tachycardia and addressing that cause. However, we do have some pharmaceutical and electrical interventions that can be used for more serious tachycardia dysrhythmias.
[Pharmaceutical Interventions] There are five classes of antiarrhythmics to be familiar with.
Class one includes sodium channel blockers such as procainamide and lidocaine.
Class two includes beta-blockers such as propranolol, metoprolol, and atenolol.
Class three includes potassium channel blockers such as amiodarone.
Class four includes calcium channel blockers such as verapamil and diltiazem.
And then class five includes other medications such as adenosine, digoxin, and magnesium sulfate.
In terms of electrical interventions, we can perform a cardioversion for a patient who has atrial fibrillation, atrial flutter, supraventricular tachycardia as well as ventricular tachycardia with a pulse.
For patients who have ventricular tachycardia without a pulse, we need to defibrillate. So remember, defib, V-fib.
Another tachycardia dysrhythmia that we need to defibrillate is ventricular fibrillation. So again, defibrillation is the electrical intervention for ventricular tachycardia without a pulse as well as ventricular fibrillation.
So that concludes my EKG interpretation video series. I hope it's been helpful for you guys. If it has, be sure to like this video, subscribe to our channel, and share a link to your classmates and friends in nursing school. And thanks so much for watching, and thanks so much for your support!
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