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.
Patricia Miller says
How does one identify those P waves as P waves and not T waves?
Jeff with admin. says
It can be difficult to identify p-waves when a patient has SVT. Most of the time they will be buried in the QRS complex. The easiest way to ensure that the patient has p-waves is to slow the heart rate down so that the p-wave can be visualized. If the rate is regular most likely there is a p-wave that is buried, and if the rhythm is irregular there is a high likelihood that the pt. has atrial fibrillation. In the case of atrial fibrillation that has a rapid ventricular rate, they will not have p-waves before the QRS complexes.
Simply put if the rate is regular there is most likely a p-wave in there. If it is irregular there is a high likelihood of no p-wave present.
Best option is to slow the heart rate down and see what is going on.
Kind regards,
Jeff
kim says
Just wondering if and at what rate to convert a stable sinus tachycardia. I think I must have missed that.
Thanks for your great work and sharing it with us!
Kim (PA-C)
Jeff with admin. says
Sinus Tachycardia is not considered an arrhythmia and would have some underlying cause that would need to be treated. For example, the following things cause stable sinus tachycardia: fever, dehydration (hypovolemia), medications, and exercise. For stable sinus tachycardia, your main action should be to reverse whatever conditions exist that are making the heart beat more rapidly.
Kind regards,
Jeff
Bob says
Jeff:
Started reviewing ACLS materials and see Re-entry SVT showing on AHA practice strips. Can you give some overview on this rhythm identification, characteristics, etc. Also, do you not have algorithm information and review on Acute Coronary Syndrome? Thanks for all the great information!
Jeff with admin. says
Thanks for contacting me. RSVT is the most common form of SVT. More specifically it is called AV nodal reentrant tachycardia. Stimulation of the atria occurs at the same time as stimulation of the ventricles. As a result, the p waves may not be seen (buried in the QRS complexes), and at times the p waves may be seen after the QRS waves. What is commonly seen as SVT is (RSVT OR AVNRT). This is the most common form of regular SVT. The main symptom is palpitation. The Review of SVT above essentially covers this type of SVT.
Atrioventricular nodal reentry tachycardia (AVNRT) is the most common type of reentrant supraventricular tachycardia (SVT). The substrate for AVNRT is the presence of dual AV nodal pathways.
I have not yet developed an algorithm AHA ACS Syndrome at the site. Here is a link to the AHA diagram.
Omaril6113 says
Hello Jeff,
thank you very much for your amazing website. It helps me with my preparation for my first ACLS. I am ashamed to ask, but please, could you explain to me the different between STABLE and UNSTABLE tachycardia? I have learned how to treat VF,VT,but still I am confused of this. Sorry for my English, it is not my mother language.
Thank you and wish you the best.
Jeff with admin. says
The difference between stable and unstable tachycardia is unstable tachycardia has progressed to the point at which blood perfusion to the vital organs is being affected and the patient is have signs and symptoms that indicate instability. Hypotension (systolic BP less than 90); changes in level of consciousness, and chest pain to name a few.
Stable tachycardia has not yet progressed to the point at which perfusion to the vital organs is being affected.
Kind regards,
Jeff
rsbdlps says
Thank you for the article you provided on AVNRT. Very informative.
Sandra says
Heard a doctor say once, that they have the patient try and blow the plunger out of a 5-10 mL syringe.
First he show’s the patient how easy it is to move the plunger by puling it back and forth in within the syringe and then he has the patient do it. Reasoning: It is usually a more “dignified” vagal maneuver, because the patient is less apt to be incontinent of stool. In which case, is the patient is concerned about embarrassing themselves in this situation and they may not bare down as forcefully as they should, as compared to blowing really hard trying to push the plunger out of the syringe. I have not seen this I action, but it sounds like a good idea.
mylee belle says
???
Kevin says
Interesting variation on the valsalva Sandra.. I’ve always liked pressing into the pts abd while they contract and resist pressing into their abd. Obviously most of the time it is something that only younger, healthier individuals can easily perform. Same concept is any vagal maneuver is that you are attempting to increase intraabdominal and intrathoracic pressure and stimulating the vagus nerve elliciting a parasympathetic response.
nora says
what about cold water splash (mammalian reflex ) I used this many times and it was effective , either splashing cold water to the face of the patient or putting iced bag on the forehead of anesthetized patient during surgery .
thanks
herb_wms says
Sounds cool, pun totally intended, but you can also get a big dose of adrenaline.
I think increased vagal tone without the adrenaline is safer. Have never read this anywhere, just my thoughts.
I like the syringe idea.
Herb
Raman says
Inverted p waves are seen in VTach because the conduction is retrograde but why in SVT?Please clarify?
Jeff with admin. says
You would not normally see p-waves in VT. In SVT, the most common type being AVNRT (Atrioventricular nodal reentrant tachycardia). P waves if visible exhibit retrograde conduction with P-wave inversion.
P waves may be buried in the QRS complex, visible after the QRS complex, or very rarely visible before the QRS complex.
Here is a detailed article from AHA on the subject.
Nabil Kamal says
Thanks for this excellent site
Nithin.k says
The rhythm shown in the above EKG is a classical A-V nodal re-entrant tachycardia (AVNRT)
kevin says
excellent site good interpretations and explanations
Beverley J Saul-Duke says
I am definitely impressed with this site and teaching.
sara says
what about the stable SVT?
Jeff with admin. says
Stable SVT would be a supraventricular tachycardia in which the patient is having no symptoms that classified as unstable (hypotension SBP<90, changes in level of consciousness, chest pain). For instance, some time ago I took care of a 50 something female with SVT (HR 160's). Here only symptom was having the feeling that her heart was racing. No chest pain, no hypotension, etc. She was stable. I hope this makes sense. Kind Regards, Jeff
Vicki Behrens says
I am one of those 50-something females who have AV nodal re-entrant tachycardia with no other symptoms. Only tachycardia …and a feeling like a 10# weight is whirling about in my chest. This started in August for me. I am excited to be scheduled for an ablation on the 16th of this month. As a B.S.N, appreciate the site also!
Holly Tays says
I really like the different examples of how it may look….thank you
nina jeffery says
This is great to be able to reivew and keep up on the acls.
Remi says
seriously,this is good teaching,you can review all this on your own time.