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SVT and the REVERT Trial

Andy Little, DO, Drew Kalnow, DO, and Mizuho Morrison, DO
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We all remember years ago when we took ACLS for the first time, once we got to the section on SVT, they would always say that we should “try vagal maneuvers” before moving to chemical conversion. Today we are going to review diagnosing SVT and re-examine all of the modalities available to those who see these patients present to the ED and Urgent Care.

Supraventricular tachycardia (SVT) is a common tachydysrhythmia in young, otherwise healthy patients and can present in any acute care setting.  Drs. Little and Kalnow from the EM Over Easy Podcast (https://emovereasy.com/) sit down with Mizuho to discuss the diagnosis and management of SVT. 

 

Pearls:

  • SVT should be considered only in patients with regular, narrow complex tachycardias.

  • Regular, wide complex tachycardias should be considered to be ventricular tachycardia until proven otherwise and referred immediately to the ED via EMS. 

  • Patients with SVT are generally stable, however, if a patient appears unstable immediate electrical cardioversion and/or EMS activation is appropriate. 

  • Vagal maneuvers with postural modification (ie: head up, bearing down, then lifting legs) is a safe and apparently effective means of converting SVT in an outpatient setting.

 

 

  • SVT is typically a narrow complex, regular tachycardia caused by electrical impulses moving in a re-entrant loop pattern that originates in the atria. 

    • The differential diagnosis for narrow complex tachycardia includes: atrial fibrillation, atrial flutter, sinus tachycardia, and SVT.

      • SVT is highly regular which can help distinguish it from Afib and sinus tachycardia.

      • A regular, wide complex tachycardia could represent SVT with aberrant conduction, however, more dangerous etiologies, namely ventricular tachycardia or Wolff-Parkinson-White, should be considered first.

      • Regular wide complex tachycardias should generally be referred to the ED immediately via ambulance, even in apparently stable patients. 

  • When a patient presents with tachycardia, assess for stability first

    • Patients with SVT may have some chest discomfort due to racing heart rate, but are generally stable. 

      • In general, think of the “Rule of 100’s” to assess stability in tachycardias: HR >100 (ie: defining tachycardia), QRS < 100 ms (narrow), and SBP >100 mmHg (not hypotensive). 

    • Activate 911 immediately for any tachycardic patient who appears unstable (e.g. significant chest pain, pale, diaphoretic, altered LOC). 

 

  • SVT most commonly presents in young, otherwise healthy patients (including children).

    • SVT is usually precipitated by one (or more) of the 3 C’s: caffeine, cocaine, and catecholamines (including those induced by exercise and other stimulants like amphetamines and ADHD meds). 

 

SVT treatment:

  • If DC cardioversion is available, it is reasonable to consider SYNCHRONIZED cardioversion in an unstable patient that you suspect has SVT starting at 50 joules while awaiting EMS.

    • If cardioverting, it is advisable to give medication for analgesia and sedation (if possible). 

  • Adenosine 6-12 mg via rapid IV push is a relatively safe and effective medication for SVT.

    • Adenosine should only be given if a cardiac monitor/defibrillator are available (not just an AED). 

    • It is important to warn patients before giving adenosine that it will cause a transient sense of impending doom. 

      • Instructing the patient to cough can mitigate the discomfort associated with adenosine. 

    • IV Calcium channel blockers (e.g. diltiazem) or beta blockers are also an option, but should only be given to patients if cardiac monitoring is available.

 

  • Vagal maneuvers are generally the safest initial treatment to try for SVT, especially in non-ED settings

    • REVERT trial (Applebaum et al, 2015) demonstrated that vagal maneuvers with postural modification were much more effective than standard vagal maneuvers for converting patients in SVT (NNT = 3). 

      • The modified vagal maneuver begins with having the patient blow into a 10 cc syringe as hard as possible for 15 seconds with the head of the bed at 45° and hips and knees bent.

      • The patient’s head is then lowered and the legs are straightened and held elevated to 30-45° 

    • This maneuver can be repeated several times.

    • Consider using cold water or ice packs to the face in young, pediatric patients to stimulate a vagal response.

  • If the patient is asymptomatic and has a normal EKG and vital signs after conversion, they can be discharged home directly from an outpatient setting.

    • Patients who have ongoing chest discomfort, abnormal post-conversion EKGs, and/or history of cocaine use precipitating the SVT to an ED for further monitoring.

 

References: 

  1. Rebel EM: http://rebelem.com/the-revert-trial-a-modified-valsalva-maneuver-to-convert-svt/ 

  1. SGEM: http://thesgem.com/2016/02/sgem147-this-is-a-svt-and-im-gonna-revert-it-using-a-modified-valsalva-manoeuvre/

  2. Appelboam A et al. Postural Modification to the Standard Valsalva Manoeuvre for Emergency Treatment of Supraventricular Tachycardias (REVERT): A Randomised Controlled Trial. Lancet 2015. [epub ahead of print] PMID: 26314489Caironi P, Tognoni 

  3. ALiEM: https://www.aliem.com/2016/03/calcium-channel-blockers-stable-svt-alternative-to-adenosine/

  4. CoreEM: https://coreem.net/podcast/episode-88-0/

James L. -

Great episode; really wonderful pearls into SVT

Mizuho M., DO -

Thanks James! Id love to hear how it works for you if/when you give it a try... let us know if it works!! :) I was failing at this time and time again until I realized I wasn't making them hold long enough...so now I go the full 15-20 seconds. Boom! Worked. Always learning! :)

Mizuho M., DO -

Thanks James! I was failing at this time and time again until I realized I wasn't making them hold long enough...so now I go the full 15-20 seconds. Boom! Worked. Always learning! :) I'd love to hear how it works for you if/when you give it a try... let us know if it works!! :)

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