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Lesson

SVT & Adenosine Framing

12 min Cardiac & ECG Skip to quiz

Objective: Name a regular narrow-complex supraventricular tachycardia (SVT). Do not give adenosine for atrial fibrillation or sinus tachycardia. If the rate is why the patient is unstable, use synchronized cardioversion.

Why this matters

Check for a pulse, then sort the rhythm before you pick a drug. Do not call every fast narrow rhythm supraventricular tachycardia (SVT). Some of it is sinus tachycardia from sepsis or volume loss. Some of it is atrial fibrillation (AF). Adenosine in the wrong rhythm does nothing useful. In pre-excited AF it can be dangerous. Sort regular versus irregular, narrow versus wide, and stable versus unstable. Then follow your protocol. See also stable versus unstable tachycardia.

Verbalize
  • Is there a pulse? If not, this is arrest, not SVT.
  • Regular and narrow: the SVT pathway may fit.
  • Irregular: think AF. Adenosine is not the treatment.
  • Unstable from the rate: pads on, then synchronized cardioversion.

What This Lesson Means by SVT

In this lesson, SVT means a regular, narrow-complex tachycardia that is likely reentry using the atrioventricular node: AV nodal reentrant tachycardia (AVNRT) or atrioventricular reentrant tachycardia (AVRT). It is not sinus tachycardia, not atrial fibrillation, not atrial flutter with variable block (the number of flutter waves per QRS changes), not junctional tachycardia, and not wide-complex ventricular tachycardia. Junctional tachycardia is not this rhythm. Do not give adenosine for it. If you cannot tell which rhythm you have, do not invent a drug.

Clinical sequence

  1. Protect the airway, breathing, and circulation. Give oxygen if the oxygen saturation is low. Get intravenous access. Get a 12-lead if it will not delay an unstable patient. Put the pads on early.
  2. Name regularity and QRS width with your systematic approach.
  3. If they are unstable because of the rate — hypotension, shock, severe altered mental status, ischemic pain, or acute heart failure — use synchronized cardioversion per protocol. Some protocols allow a brief adenosine trial for regular narrow-complex tachycardia while the pads go on. That is not permission to delay a shock in an unstable patient.
  4. If they are stable, try a vagal maneuver, such as Valsalva or modified Valsalva if you are trained. Then give adenosine if protocol includes it: a rapid IV push with a flush, on a monitor, with the pads already on.

How adenosine fits

  • Adenosine works on the atrioventricular node. That is why it can stop AVNRT or AVRT, and why it is the wrong treatment for atrial fibrillation. You may see flutter waves for a moment. That is not a plan to convert atrial fibrillation.
  • Do not give AV-node blockers — adenosine, diltiazem, verapamil, beta-blockers, or digoxin — in suspected pre-excited AF (WPW, Wolff-Parkinson-White). You can speed conduction down the extra pathway into VF (ventricular fibrillation). An irregular, very fast, wide or changing QRS is the warning. Cardiovert if unstable. Use the protocol path if stable.
  • Warn the patient that they will feel bad for a few seconds. Record a strip during the push.
  • This site does not publish milligrams. Protocol owns the dose, the repeat dose, and reduced-dose situations such as a central line, a transplant, or drugs on the teaching list such as dipyridamole or carbamazepine.

Common errors

  • Giving adenosine for sinus tachycardia at 130 from fever or bleeding.
  • Calling an irregular narrow-complex rhythm SVT.
  • Pushing adenosine with no pads on.

Practice

One-minute check

In CardioStrip, pick a regular narrow tachycardia and an irregular narrow tachycardia. For each, say: vagal/adenosine path, rate-control path, or cardioversion path — and why.

Related: AF with RVR, WCT.

Sources & Further Study

Named guidelines for further study. They are not clinical orders and do not replace your protocol or medical direction.

Education only. Apply learning within your protocols and medical direction. This is not clinical care guidance.

Check Your Understanding

Questions drawn only from this lesson. After you check, the key is highlighted. Education practice — not a certification exam.

1. The SVT pathway in this lesson is for:
2. A crashing patient whose instability is from a regular narrow tachyarrhythmia:
3. Adenosine (and other AV-node blockers) are the wrong move in:
4. Irregular narrow-complex tachycardia at 160 is best treated as:
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