SVT is a broad term for a number of tachyarrhythmias that originate above the ventricular electrical conduction system (Purkinje fibers).
Classic Paroxysmal SVT has a narrow QRS complex & has a very regular rhythm. Inverted P waves are sometimes seen after the QRS complex. These are called retrograde p waves.
The heart fills during diastole, and diastole is normally 2/3 the cardiac cycle. A rapid heart rate will significantly reduce the time which the ventricles have to fill. The reduced filling time results in a smaller amount of blood ejected from the heart during systole. The end result is a drop in cardiac output & hypotension.
With the drop in cardiac output, a patient may experience the following symptoms. These symptoms occur more frequently with a heart rate >150 beats per minute:
- Shortness of air (S)
- Palpitation feeling in chest (S)
- Ongoing chest pain (U)
- Dizziness (S)
- Rapid breathing (S)
- Loss of consciousness (U)
- Numbness of body parts (S)
The pathway of choice for SVT in the tachycardia algorithm is based on whether the patient is stable or unstable. The symptoms listed above that would indicate the patient is unstable are noted with the letter (U). Stable but serious symptoms are indicated with the letter (S).
Unstable patients with SVT and a pulse are always treated with synchronized cardioversion. The appropriate voltage for cardioverting SVT is 50-100 J. This is what AHA recommends and also SVT converts quite readily with 50-100 J.
Below is a short video which will help you quickly identify supraventricular tachycardia on a monitor.
Please allow several seconds for the video to load. (4.37 mb)
Click for next Rhythm Review: Atrial Flutter
Questions Asked On This Page
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Q: What are vagal maneuvers?
A: A vagal maneuver is a technique by which you attempt to increase intrathoracic pressure which stimulates the vagus nerve. This can result in slowed conduction of electrical impulses through the AV node of the heart. The following methods can be used.- Cough Method: Have a patient cough forcefully. This is a simple form of vagal maneuver. A cough stimulates an increase in intrathoracic pressure which will stimulate the vagus nerve. This can result in slowed conduction of electrical impulses through the AV node of the heart.
- Straw Method: Have the patient blow forcefully through a straw for 3-5 seconds.
- Bear down Method: Have the patient bear down and strain. Kind of like how a person might strain when having a bowel movement.
- Syringe Plunger Method: First, show the patient how easy it is to move the plunger by pulling it back and forth in within the syringe. Now instruct the patient place their mouth over the exit end of the syringe and attempt to blow the plunger out of the syringe. Have them blow for 3-5 seconds.
- Abdominal Pressure Method: Press into the patient’s abdomen while they contract and resist pressing into their abdomen.
- Ice Method: Quote from a healthcare provider: “We had a kid (approximately 12 yrs old) present to our ER in SVT, instead of using drugs and vagal maneuvers we dunked his face in a bucket of ice twice, and it immediately & effectively brought the heart rate down. We observed him for a period of time, and the kid was fine. Worked wonders! Young army doctor’s idea!”
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Q: I can’t distinguish the sinus tachycardia example from the three re-entry SVT examples on the pre-test no matter how long I stare at the strips…they look identical to me. Help please, and thanks.
A: On the Pretest at the AHA website, Look at each image carefully. Don’t try to over-observe. Just look at each one and notice how many QRS complexes there are.
There are almost double the amount of QRS complexes in all of the SVT when compared to the Sinus Tachycardia. This is the easiest way to tell SVT from Sinus tachycardia. Also, P-waves are only clear in the sinus tachycardia. Most of the time with SVT you will not be able to see the p-waves. SVT rate will usually be greater than 150 and Sinus tachycardia will be less than 150. -
Q: Let me get this straight. Svt is a heart rate greater than 150 with conduction at or above the av node?
A: That is correct.
aclsstudy says
In stable SVT we start with vagal maneuvers,right. My question is what should be the duration of time to perform vagal maneuvers.
Jeff with admin. says
Vagal maneuvers should be attempted for 5 to 10 seconds.
This should be enough time to stimulate the vagus nerve.
Kind regards, Jeff
Mona says
There are several different vagal maneuvers, and not all of them work in the same patient. I have had SVTs for many years that respond well to bearing down on holding breath for a bit, but the other day I ended up in ER for the first time and the MD tried carotid massage with no effect at all, and it was extremely unpleasant to boot. So I would suggest that in cases when you have the time and the patient is lucid and cooperative, and one vagal maneuver fails, try a different one…
Jeff with admin. says
Yes, this is correct. You can use another method if one fails to work.
Kind regards,
Jeff
Brie says
This is site is so helpful!!! Thank you!!!
Kristy says
Hi I have enjoyed your site we will see how I do tomorrow on the exam . In the mean time if you can fix the SVT video . I cannot get it to download and or play 🙁
Thank you
Kristy
Jeff with admin. says
Thanks for leaving a comment. I checked the video and it seems to be functioning properly. You may need to restart your computer. On rare occasions, the videos can hang up when downloading and a the best cure is to restart your computer. Please let me know of you need any further help.
Kind regards,
Jeff
Candice Chesno says
How to distinguish between SVT and sinus tach?
Jeff with admin. says
The rate for SVT will usually be greater than 150. With sinus tachycardia, the rate will usually be less than 150. Sinus tachycardia is usually related to some underlying cause like hypovolemia, fever, or sepsis and the rate will not exceed 150.
This is the easiest way to determine the difference.
For SVT, the symptoms can arise suddenly and may resolve without treatment. The rate for SVT will typically be 150-270/min and will often be accompanied by the following sympotms: pounding heart, shortness of breath, chest pain, rapid breathing, dizziness, or loss of consciousness.
Kind regards,
Jeff
ESA says
adenosine IVP
how many ccs of normal saline DO WE USE SINCE IT HAS A SHORT HALF LIFE?
Jeff with admin. says
You would follow the dosage of adenosine with 10 ml of NS. You should have the 10 ml on a double port IV or put a 2nd port on with a stop-cock. This way you can push the adenosine in rapidly and then with as short a time as possible you can forcefully push the 10ml bolus of NS in. You must push both extremely fast. The faster the better.
Kind regards,
Jeff
Paul Catum says
Great site! FYI, some of the EM residents I work with showed me a good resources for learning reviewing 12-lead ecgs. For example, the supraventricular tachycardia ecg page is here: http://www.emedu.org/ecg/svt.htm
It has a bunch of SVT variants as well, and you can look at a strip and then hover your mouse to see the markup. Pretty cool.
Jeff with admin. says
Thanks for sharing your comments and the link to the 12-Lead ECG examples site. Kind regards, Jeff
dmcadam says
Jeff,
How can you tell the difference in coarse VT/VF as to monomorphic and polymorphic?
Jeff with admin. says
There is no such thing as coarse VT.
Kind regards, Jeff
James Whitney says
I think dmcadam is getting at is the ACLS pretest differentiates between fine and coarse VFIB.
Jeff with admin. says
Watch the video at the bottom of this page to see the difference
ruth says
Hi Jeff,
What is the easiest way of recognising reentry supraventricular tachycardia on a rhythm strip? also couldn’t find much detail on vagal maneuvers in the provider manual?
great site btw!!:)
Chris with admin. says
The 4 most common types of SVT are A-V Nodal Reentry Tachycardia, A-V
Reentry Tachycardia, atrial tachycardia and atrial flutter. These rhythms
are regular in nature and have a rate > 150. To distinguish the difference
between the re-entry tachycardias and the other types really requires a 12
lead ECG. The diagnostic criteria to determine that it is a reentrant
tachycardia is actually quite complex. I attached a pic from my 12 lead ecg
pocket reference that will help. Reentry tachycardias are very easy to
convert and often vagal maneuvers will suffice to terminate the tachycardia.
Kind regards,
Chris
Buzzi says
When is putting pressure on the jugular used, in this type of scenario?
Jeff with admin. says
Applying pressure or lightly massaging carotid artery would be considered a vagal maneuver. This or any type of vagal maneuver would be performed for symptomatic SVT if the patient is stable and the QRS complex is less than 0.12 second.
Kind regards,
Jeff
jgrice says
Let me get this straight. Svt is a heart rate greater than 150 with conduction at or above the av node?
Jeff with admin. says
That is correct.
Kind regards,
Jeff
Noel says
I realise that “unstable patients” benefit more with cardioversion. Would it be unacceptable to attempt adenosine administration if cardioversion is delayed? If so, why. I could not find any information on adenosine to say that it would be contraindicated or even cautioned with associated hypotension (or other S&S of instability).
Jeff with admin. says
The decision point in the tachycardia algorithm for whether to use cardioversion or adenosine is patient stability. However, if you look at box 4 on the AHA tachycardia algorithm diagram, there is the option to consider use of adenosine if the rhythm is a regular narrow complex tachycardia. This consideration of adenosine would be most advantageous if adenosine administration occurred during setup for cardioversion. The main reason why you would want to use cardioversion in the unstable patient is related to the patient’s cardiovascular compromise. If for some reason cardioversion was delayed, adenosine could be an option in the patient with a regular narrow complex tachycardia.
Kind regards,
Jeff
Artemis says
Here is an urgent question. I am taking the course this week end. Today we had the lecture about tachycardias. The instructor persisted that maximum dose for adenosine is still 30 mg (6,12,12) and I got confused…What information should I keep??
Jeff with admin. says
Your instructor is wrong. The prefilled vials even come as 12 mg doses. I have no idea where he is getting 30mg for the adenosine dose. The dosing is now (6,12). I have not been able to determine why AHA is not recommending (6,12,12) any more, but I would use the third dose if necessary.
In class, I would do whatever your instructor says, but I would stick with the guidelines in real life. Also if you are taking the actual AHA exam and are asked about adenosine, I would use the 6, 12.
Please let me know if you have any further questions.
Kind regards,
Jeff
kathy gee says
Is the 30 mg maximun dose coming from 6 + 12 + 12 = 30mg?
Jeff with admin. says
This could be what the person asking the question was meaning. However, there is no maximum dosage that is stated for adenosine. Adenosine is actually rapidly metabolized by the body.
Kind regards,
Jeff
honeytoy says
i was wondering why there is nothing on stroke and acute mi since this is now on the acls with drugs
Jeff with admin. says
You can find information on Stroke and ACS protocol in the practice test library at this link: Practice Test Library
They are toward the bottom of the page.
Kind regards,
Jeff
mgnllthppl says
I can’t distinguish the sinus tachy example from the 3 re-entry SVT examples on the pre-test no matter how long I stare at the strips…they look identical to me. Help please, and thanks.
Jeff with admin. says
On the Pretest at the AHA website, Look at each image carefully. Don’t try to over-observe. Just look at each one and notice how many QRS complexes there are.
There are almost double the amount of QRS complexes in all of the SVT when compared to the Sinus Tachycardia. This is the easiest way to tell SVT from Sinus tachycardia. Also P-waves are only clear in the sinus tachycardia. Most of the time with SVT you will not be able to see p-waves. SVT rate will usually be greater than 150 and Sinus tachycardia will be less than 150.
Kind regards,
Jeff
Vic says
Great place to learn about ECG’s ! I’ll become a member when I get back from vacation.