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Supraventricular Tachycardia


Supraventricular Tachycardia (SVT)

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

Supraventricular Tachycardia EKG Rhythm Strip

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 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.

  106 Responses to “Supraventricular Tachycardia”

  1. Can you call PAF and PAT—SVT?

    • Yes, premature atrial tachycardia (PAT) would be considered a of supraventricular tachycardia. Not sure what you mean by PAF, but if you mean atrial fibrillation with a rapid ventricular rate then yes, this would also fit the criteria for SVT.

      Kind regards,

      • We usually refer : PAT and PAF as paroxysmal atrial tach and paroxysmal atrial fibrillation when the event starts suddenly, and many SVT events do start suddenly

  2. How do you differenciate SVT from reentry SVT

    • 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,

  3. Lets say I have a pt hooked up to a basic tele monitor and she goes into SVT. Vagal maneuvers are attempted and doctor orders Adenosine. Would you then hook her up to the code cart prior to giving the Adenosine.?

    • Oh and the patient is in stable condition.
      And would your answer be different if the patient had multiple reentrys into SVT and successful Adenosine administrations? Or maybe just having the code cart at bedside? Can Adenosine cause lethal arrhythmias?

      • The crash cart would not be necessary, but it could be close at hand in the case that the patient becomes unstable. Adenosine does not normally precipitate lethal arrhythmias.

        Kind regards,

    • Having the code cart prior to giving adenosine would not be necessary. It would not hurt, but it would not be necessary. Adenosine rapid IV push will not usually precipitate pulseless VT or VF.

      Kind regards,

  4. How can we treat svt in hypotensive patient <90 systolic , while refusing dc shock?

  5. What’s the difference between a stable and unstable patient. Does dsypnoea and palpitations in a patient discovered to have an SVT make him unstable. Would it be right to shock him immediately or better to do Valhalla manoeuvre then adenosine algorithm.

    • The main indication of a patient that is unstable are as follows:
      1. Altered mental status
      2. SBP less than 90 (hypotension)
      3. Signs of shock
      4. Ischemic chest discomfort
      5. Acute heart failure

      The patient with dyspnea and palpitations would not necessarily be unstable, and it would most likely be ok to attempt vagal maneuvers then adenosine prior to any attempt with cardioversion.

      Kind regards,

  6. Sorry the errors!

  7. In the third example on the video it states that you can see p waves. Well, if that’s true, then where are the T waves? In the explanation blurb at the beginning it says that p waves can be buried in the qrs. How are you ever supposed to know if you are looking at p waves or t waves?

    • With SVT, It can be difficult to differentiate the p-waves from the t-waves. Most of the time p-waves will not be present due to the rapid HR involved with SVT.
      One way to differentiate is to give adenosine to temporarily slow the heart rate. This will give you a better look at the underlying rhythm and help to diagnose the underlying rhythm.

      Kind regards,

      • Ni jeff. Another forma to find p waves and t waves in some cases justo gain 2 mV and increase TVE speed 50mm/sec. Bye!

  8. Will synchronised cardioversion always convert an unstable SVT? and if not is it acceptable to administer adenosine in the case of a “SVT refractory to cardioversion”.

  9. How can you tell the difference between SVT and Atrial Tachycardia? The strip I have has a rate of 180, regular rate, distinguishable P waves. I say SVT but it’s Atrial Tach?

    • Atrial tachycardia is a form of SVT. Atrial tachycardia means that the tachycardia originates in the atria but not from the SA node.

      When describing a tachycardia that originates in the atria but outside of the sinus note, another term used is supraventricular. Thus, atrial tachycardia is essentially the same thing as SVT.

      Kind regards,

    • Svt = a rate > 150 bpm

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