Background
- SVT = atria or AV node are sustaining the tachycardia
- Most are AV nodal re-entry tachycardia (AVNRT), AN re-entry tachycardia (AVRT), or atrial tachycardia (AT)
- AF more likely in older
- M = F
- "SVT" in 0.2% population, AF circa 1%
Clinical
Symptoms
- Palpitations (abrupt on/offset except sinus = slow on/offset)
- Chest pain
- SOB
- Pre-syncope
Types
AVNRT
- Re-entrant circuit into AVN
- 1 fast, 1 slow path into AVN = "circular" circuit
- Slow pathway trigger then impulses move retrograde via fast path to the atria
- P waves invisible in QRS (pseudo RSR' in V1)
- Some get delta wave (if slow path = very slow - WPW)
Atrial tachycardia
- AbN impulse formation or re-entrant
- Focal or multifocal (unwell patient or Dig toxic)
- P waves have different morphology in multifocal
AVRT (incl. WPW)
- In sinus some impulse pass via the accessory pathway, early Vent. excitation (delta wave) but narrow QRS (most of the rest of the impulse down through His-Purkinje system)
- In orthodromic AVRT, antergrade down His-Purkinje and retrograde up via accessory pathway = narrow complex tachy
- Less common = antidromic AVRT = antegrade via accessory pathway and retrograde via AV node = broad complex tachycardia
DDx narrow complex tachy.
- Sinus
- Atrioventricular nodal re-entry tachycardia (AVNRT)
- Atrioventricular re-entry tachycardia (AVRT)
- Atrial tachycardia
- Atrial flutter
- AF
- Sinus node re-entry
- Junctional tachycardia
Management
- DC version if haemodynamically unwell (esp. if ?VT)
- Modified valsalva
- Reverse valsalva
- Adenosine 6/12mg iv (have defib. ready and beware bronchospasm)
- Most important ECG = rhythm strip on termination (record all)
- Verapamil 5mg IV
- Remember anticoagulation if AF or SVT duration >48hrs
- Please avoid carotid massage
Modified valsalva (1)
Good evidence (RCT).
- Patient semi-recumbent
- Strain of 40 mm Hg pressure (blow 10ml syringe plunger) x 15 sec
- Lie patient supine
- Assistant elevates legs to 45°
Reverse valsalva (2)
Case series.
- Exhale without forcing while sitting
- Pinch nose and close mouth tight
- Inhale against resistance for 10 sec
Links
References
- REVERT trial. Lancet 2015 DOI:https://doi.org/10.1016/S0140-6736(15)61485-4
- The reverse vagal manoeuvre: Am J Emerg Med 2021. DOI: https://doi.org/10.1016/j.ajem.2020.12.061