• Is the patient hemodynamically stable?
• Is the QRS > 0.12 seconds: VT or SVT with aberrancy?
• Is the rhythm regular or irregular?

• Paroxysmal supraventricular tachycardia (PSVT) is characterized by episodic tachycardia with an abrupt onset and resolution.
• PSVT describes atrioventricular nodal re-entry tachycardia (AVNRT), atrioventricular re-entry tachycardia (AVRT) and ectopic/atrial tachycardia (AT). Atrial flutter and atrial fibrillation are discussed elsewhere.
• PSVT is a common presentation in the emergency department for which several treatment options exist¹.
• It is important for practitioners to rule out ventricular tachycardia (VT) when diagnosing PSVT.

• Suspect PSVT in all tachycardic patients.
• Standard diagnosis of PSVT requires an ECG. Typical findings include:
  • Regular rhythm.
  • Narrow QRS complex
    • PSVT with aberrancy will present with a wide QRS complex.
  • Atypical P wave morphology (absence of P waves or P waves after QRS complex)
    • P waves preceding the QRS complex can be seen, causing it to resemble sinus tachycardia.
• Successful treatment of a PSVT with a vagal maneuver or adenosine confirms the diagnosis of PSVT.
• PSVT vs Sinus Tachycardia
  • Suggestive of ST:
    • A precipitating cause/event is identified.
    • The rate varies with respiration or positional changes.
    • The rate gradually slows with vagal maneuvers.
  • If the heart rate exceeds 220 minus the patient’s age, ST is much less likely.
• PSVT vs Atrial Flutter 2:1
  • Atrial flutter with 2:1 conduction may present on ECG without characteristic flutter waves, suspicious of atrial flutter with 2:1 conduction if:
    • Heart rate is around 150 bpm.
    • Flutter wave appears (atrial flutter may briefly conduct as 3:1 instead of 2:1, uncovering flutter waves).
    • Vagal maneuvers or adenosine treatment uncover flutter waves.
• PSVT + Aberrancy vs VT
  • Wide complex PSVT due to accessory pathway or pre-existing bundle branch block may not be readily discernible from VT on ECG. The Brugada criteria was demonstrated to have 90% sensitivity and 64% specificity in a recent meta-analysis.

Acute Management

• Hemodynamically Unstable
  • Signs include: altered mental status, significant cardiac chest pain, hypotension (SBP < 90 mmHg), or pulmonary edema.
  • Synchronized DC Cardioversion
    • Adults | Initial trial at 50 J. If unsuccessful, repeat with 100J.
    • Pediatrics | Initial trial at 0.5-1 J/kg. If unsuccessful, repeat with up to 2 J/kg.

Note: Equal efficacy and safety has been demonstrated between biphasic and monophasic cardiac defibrillator monitors. However, biphasic monitors generally require less energy for the same efficacy and should be used if available.

• Hemodynamically StableFirst Line
  • Vagal Maneuvers: Valsalva Maneuver
    • The modified Valsalva maneuver (REVERT Trial) is shown to have greater efficacy than the standard method (43% vs 17% cardioversion in SVT).
    • Patient in a seated position blows into a 10mL syringe for 15 seconds, with just enough force to barely move the plunger.
    • Immediately lay the patient supine and lift both legs vertically in the air for another 15 seconds.

https://sjrhem.ca/modified-valsalva-maneuver-in-the-treatment-of-svt-revert-trial/

https://emergencycarebc.ca/clinical_resource/modified-valsalva-manoeuvre-for-supraventricular-tachycardia/

• • Carotid Sinus Massage (CSM): Auscultate to rule out carotid bruits. Serious neurological effects (0.13%) rare but reported in elderly populations.³ 
  • Adenosine
    • Double Syringe Method | 6mg adenosine IV followed by 20mL NS bolus. If unsuccessful, repeat with a second dose of 12mg.
    • Single Syringe Method | 6mg adenosine IV diluted with up to 20mL of NS. If unsuccessful, repeat with a second dose of 12mg diluted with up to 20mL of NS.
    • A randomized trial from 2022 found moderate quality evidence to suggest no difference in cardioversion success rates between the two methods⁴. Although underpowered, this study suggests the single syringe method may be useful for clinical scenarios where physical limitations prevent the successful use of the traditional double syringe method.
    • Halve dose to 3mg in patients taking dipyridamole or carbamazepine.
    • Avoid in patients with 2^nd or 3^rd degree AV blocks.
  • Calcium Channel Blockers (CCBs)
    • Diltiazem | 0.25mg/kg IV, increased to 0.35mg/kg IV if unsuccessful.
    • Verapamil | 2.5-5mg IV, increased to 5-10mg IV if unsuccessful.

Although AHA guidelines list CCBs as a second-line intervention, moderate-strong evidence suggests CCBs are comparable to adenosine in in ​efficacy⁵. Moreover, a number of reports suggest an increased rate of adverse events with adenosine as compared to CCB treatment. Clinicians should not hesitate to use CCBs in place of adenosine when clinical judgement dictates.

Note: Only non-dihydropyridine CCBs possess the cardiac selectivity required to be effective PSVT therapeutics.

• • Beta-Blockers
    • Use in cases of acute PSVT where adenosine/CCBs have failed, or prophylactically for long term prevention of PSVT.
    • Adenosine and CCBs are contraindicated in patients with evidence of (VT) or wide complex tachycardia (WCT). Use of these therapeutics in patients where VT and WCT have not been ruled out but may put the patient at risk of becoming hemodynamically unstable.

               Third Line

• • Synchronized DC Cardioversion
    • Reserved for patients who are unresponsive to vagal maneuvers and Adenosine or where VT cannot be ruled out. See above for dosage details.

Long Term Management

• Isolated Episode of PSVT and No Comorbidities
  • Follow-up with a family physician. Holter monitoring may be pursued.
• Recurrent PSVT With No Pre-Excitation
  • At-home vagal maneuvers are the first line intervention for future events.
  • Patients with chronic hypertension may benefit from long-term suppressive therapy using beta-blockers or CCBs.
  • Normotensive patients not responding to vagal maneuvers may benefit from a cardiologist referral.
• Recurrent PSVT With Pre-Excitation
  • Refer to cardiology for electrophysiology and follow-up. Catheter ablation may be warranted in some of these patients.

Patients with PSVT will rarely be admitted to hospital unless they remain hemodynamically unstable or develop acute episodes associated with comorbid conditions.

Transport to another facility is rarely required unless the current facility lacks the necessary resources to manage the unstable patient.

Until PSVT is confirmed and resolved, patients should be monitored for changes in hemodynamic stability and complications of potential PSVT mimics, including WCTs and VT.

• Patients may be discharged if they are stable and their episode of PSVT is resolved.
• Discharged patients should be educated on vagal maneuvers that they can try at home during future episodes of PSVT.
• Patients presenting with their first episode of PSVT may follow-up with their family physician.

1. Modified Valsalva Maneuver — https://emergencycarebc.ca/clinical_resource/modified-valsalva-manoeuvre-for-supraventricular-tachycardia/

   Two Syringe Adenosine Method — https://www.youtube.com/watch?v=WBQrddqWhzo

    

   
   

1. Link MS. Evaluation and Initial Treatment of Supraventricular Tachycardia. NEJM. 2012;367:1438-1448. Available from: https://www.nejm.org/doi/10.1056/NEJMcp1111259?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed

   
   

2. Sun X, Teng Y, Mu S, Wang Y, Chen H. Diagnostic accuracy of different ECG-based algorithms in wide QRS complex tachycardia: a systematic review and meta-analysis. BMJ Open. 2023;13e069273. Available from: https://bmjopen.bmj.com/content/13/7/e069273.info

   
   

3. Walsh T, Clinch D, Costelloe A, Moore A, Sheehy T, Watts M et al. Carotid sinus massage — How safe is it? Age and Ageing. 2006;35(5):518-520. Available from: https://academic.oup.com/ageing/article/35/5/518/10005?login=true

   
   

4. Kotruchin P, Chaiyakhan I, Kamonsri P, Chantapoh W, Serewiwattana N, Kaweenattayanon N et al. Comparison between the double-syringe and the single-syringe techniques of adenosine administration for terminating supraventricular tachycardia: A pilot, randomized controlled trial. Clinical Cardiology. 2022;45(5):583-589. Available from: https://onlinelibrary.wiley.com/doi/10.1002/clc.23820

   
   

5. Alabed S, Sabouni A, Providencia R, Atallah E, Qintar M, Chico TJA. Adenosine versus intravenous calcium channel antagonists for supraventricular tachycardia. Cochrane Database of Systematic Reviews. 2017; Issue 10. Art No.: CD005154. Available from: https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD005154.pub4/full