Clinical Case 123: How we do SVT Better

This case is inspired by a recent Twitter chat involving Seth Trueger, Chris Hicks, myself and the eternal opposition -Dr le Cong. There were others involved – thanks for joining the conversation to prove Minh wrong ūüôā

So here is the case:

Barry is a 27 yo bloke who has never had a sick day in his life.

He was playing beach volleyball as he does every week when he went for a big ¬†dive.. He made a great save, hit the sand hard with his chest and jumped up to get the next ball. But he felt his heart racing immediately – it felt like it was jumping out of his chest. He played on until the end of the set. When he sat down for a break he noticed his Fitbit watch showed his pulse at 150/ min. After 5 minutes rest it was still 150 flat. He felt vaguely dyspnoeic, but played on. Now an hour later he is in the ED wondering “what is the problem…”

here is his triage ECG

Courtesy LITFL ECG Library

Courtesy LITFL ECG Library

This is Typical “slow-fast” AVNRT ¬†SVT. So easy, we know what to do.

My practice for the previous decade or so has been to try a few budget vagal manoeuvres, then slug in a bolus of adenosine. This almost always works. Patient goes back to sinus rhythm and goes home  problem solvered! So what is the problem?

Well we all know that the slug of adenosine comes with a 100% risk of making the patient feel like crap, dying, falling, going mad for half a minute or so. ¬†But it is so much fun! For us – not the patient! We get to see a medical miracle on the end of a syringe, impress the Med Students and feel like a God with healing hands… ¬†Meanwhile our patient is in a state of abject panic.

Now of course, if it doesn’t work we can just double the dose, maybe even consent the patient to round 2 of la petit mort… Good luck selling that.

Fortunately for Bazza, there is a better way. So how do I do SVT in my ED circa 2015?

I will take you through it step by step.

  1. Bring Barry into a bay and put him on a monitor, sit him up and explain what is going on. Empathy and reassurance will reduce his endogenous catecholamine load and make all the subsequent steps easier. He will not wonder why you are doing all these odd things to him!
  2. Grab a sphygmomanometer tube and show him how to blow the meter up to 40+ mmHg as per the REVERT trial. Blow into the tube and hold it up for 15 seconds.
  3. Now explain the process to him. He will blow into the tube for 15 secs, then we will drop his bed back into mild Trendelenburg and lift his feet up to 45 degrees.  The augmented Valsalva, voila!  In the REVERT trial this move worked 43% of the time.  Nearly half of SVTs were fixed with a 1 minute, no risk, simple, free intervention. There is nothing not to like here!

 Here is the video from the Lancet edition in which the REVERT trial was published – 2 minutes….

But 57% of Barrys will still be in SVT after the REVERT-style Valsalva move.  So next move?

4.  In the past we would usually reach for the adenosine about now  Рbut I think there is a better option. Verapamil.  So at this point I will ask the team to make up 20 mg of verapamil in a 20 ml syringe. This usually takes 5 minutes Рso in that time I will try the augmented Valsalva a few more times to pass the time. Why not?

There is a metanalysis from 2011 in Europ Journ of EM by Aussie researchers that shows both adenosine & verapamil work in 9 out of 10 cases.

Here is where it gets interesting. Both are equally effective – so which one has the most side effects? Which one would you want if you were in SVT and Valsalva didn’t work?

We know that verapamil has more BP effect Рabout 4% hypotension vs. 1% for adenosine.  But the degree of hypotension seen is not really clinically relevant Рabout 10 Р15 mmHg in systolic BP.

Adenosine has more side effects (OR of nearly 12:1 ) – and when you consider that SVT is a recurrent problem… adenosine seems particularly torturous. I imagine the side effects counted in these trials are things like BP or other non-patient oriented outcomes. So hard to say how many really didn’t like the death pause of adenosine?!

5. I put in an IV and give 2 mg of the verapamil mix every few minutes until either the patient reverts, or the syringe is empty.  I have never had a patient experience anything remotely unpleasant during this titration. In my small experience they have all reverted in the teens РI.e. Between 12 Р16 mg used.  A few have had small, asymptomatic BP falls. All went home happy.

6.  If they are not reverting then it is not unreasonable to retry the Valsalva trick with the verapamil on board..

7. This is a cognitive STOP point. ¬†If we have done all of this and still not winning – then I pause here and reconsider the diagnosis. Send the ECG to my local Cardiologist (2000 km away) to check I am not missing anything. Do a bedside ECHO – just check they don’t have a massive LA or something else that might be an underlying cause.

8. ¬†At this point – if all still suggested benign SVT I would consider switching to adenosine. ¬†The guidelines all say we should start with 6 mg, then go to 12 and then…. ¬†But why? It is a drug that wears off quickly, doses mean little. ¬†so why not give a decent whack first time and avoid the potential need to use it 5 minutes later on the now terrified patient ? So my practice is to put in a good proximal IV, put 12 mg in a big syringe and flush it in as fast as I can to get maximal effect.

Chris Hicks suggested sedation for the adenosine pause Рand I think this is reasonable if you think the patient is the anxious type.  Of course, that sedation will likely drop the BP more than the verapamil would!


That is how I now roll when it comes to treating SVT.  Love to hear your thoughts..




  1. Still have access to a manual BP cuff? Mercury or aneroid?

  2. I sensed my name being taken in vain so felt compelled to respond here!

    As you point out adenosine and verapamil revert SVT as well as each other. so it then comes down to cost, side effects, etc.

    I dont doubt that adenoside is more expensive. But you also cannot argue that verapamil is safer. Its a CCB and causes hypotension. Once you give it, you should be very careful about giving any other AV nodal blocking agent. The reverse is not the same for adenosine due to its very short half life. You can trial adenosine then any other AV nodal blocking agent you want. Cant do that with verapamil as your opening gambit!

    as for the impending doom blahblah, patient empathy aspect ..well why dont you burn incense candles and lavender oil in the ED resus room as well!

    • Geoffrey Menzies says

      Yes. Verapamil for me seems a drug of last resort (after fax and phonecall and maybe the patient’s usual flecainide). Once it is in, no more CCB, no beta-blocker. Just more verapamil until tomorrow.

  3. anne creaton says

    In Fiji if valsalva doesnt work we would use adenosine or Verapamil depending on which one was in stock that week. If we have both we would use one based on patient comorbidities, anxiety (rare here) and clinician preference. We had neither for a while and I believe that there were a few cardioversions…
    Love REVERT. More pragmatic trials like this would be great.

  4. How much time does it take to give 2 mg of Verapamil every few minutes until they revert vs the time it takes for adenosine?

    I usually start with “Kapur’s Triple Therapy” first: Valsalva while the patient is in Trendelenberg and I’m doing CSM simultaneously. But if that doesn’t work, I’m thinking the Verapamil protocol you suggest will take a fair bit more time.

    • Hi Atul
      the time to give verapamil is dependent on dose required. 2 mg every 2 minutes takes 20 minutes. I usually get a Med student or trainee nurse to stand and deliver it – it is a great way to learn about physiology!
      Time to give drug is not really something that slows care in my experience – it is never the “rate limiting step” [pun intended].

      I think most patients would be happy to spend 5 more minutes in order to avoid the death spiral symptoms!

  5. For the adenosine, are you pushing and flushing, or mixing it with the flush?

  6. Dean Burns says

    Hi Casey

    I had an interesting SVT case yesterday. A 56 yo man, fit & well having been walking in the Yorkshire Dales over the weekend. He presented to his GP with a chief complaint of abdominal bloating. The GP checked his pulse & performed an ECG which showed SVT at a rate of 194 bpm. He was asymptomatic.
    He was otherwise well & drank about 5 coffees per day.
    Adenosine was tried initially 6, 12mg. Transient slowing only followed by a continuation of SVT. We tried a REVERT style vagal manoeuvre with no joy. 18 ->24mg of adenosine resulted again in transient slowing of his HR and then speeding up into the SVT rhythm. We then started verapamil 5mg slow IV push over 5 mins. 15mg later he had slowed to sinus rhythm. I was wondering if anyone else has experienced a struggle to cardiovert SVT in patients who’ve been in that rhythm a long time (perhaps several days) & whether there’s an electrical remodelling in the heart, in the same way that AF begets AF.


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