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Educational draft · awaiting clinical reviewUse Rapid for revision, not patient-care decisions. Check current national and local guidance and the BNF or BNFC before acting.

Supraventricular tachycardia

Cardiology · UK scope · Sources checked 25 Aug 2026 · Clinical review pending

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Escalate

Any tachyarrhythmia causing shock, syncope with severe/ongoing hypotension, myocardial ischaemia, severe heart failure/pulmonary oedema or occurring immediately post-ROSC requires synchronised cardioversion rather than serial drug trials.

Synopsis

Use QRS width, regularity and haemodynamic state to diagnose and safely terminate adult SVT without giving AV-nodal blockers to a dangerous mimic.

  • SVT is a mechanism group, not one ECG diagnosis: common regular narrow-complex causes are AVNRT, orthodromic AVRT, atrial tachycardia and flutter with fixed conduction.
  • An abrupt-onset, very regular narrow tachycardia with hidden or retrograde P waves suggests AVNRT/AVRT, but obtain a 12-lead during symptoms whenever this does not delay emergency care.
  • Classify first by stability, QRS width below or at least 120 ms, and regularity.
  • Stable regular narrow SVT: modified Valsalva is a good first manoeuvre; avoid carotid massage when carotid disease/bruit or prior TIA/stroke makes it unsafe.
  • Current RCUK 2026 adenosine regimen is 6 mg, then 12 mg, then 18 mg as rapid IV boluses if unsuccessful and if there is no pre-excitation.
  • Important UK discrepancy: several current adenosine SmPCs license 3 mg, then 6 mg after 1-2 minutes, then 12 mg after another 1-2 minutes and state that higher doses are not recommended.
  • Adenosine may terminate AV-node-dependent SVT or transiently expose flutter/atrial tachycardia; record continuous/multilead ECG through each dose.
  • Treat an undifferentiated regular broad-complex tachycardia as VT. Adenosine is considered only for regular monomorphic suspected SVT with aberrancy and no pre-excitation.
  • Irregular broad pre-excited AF is a cardioversion/procainamide problem, not an adenosine, verapamil, beta-blocker or digoxin problem.
  • Recurrent symptomatic AVNRT/AVRT merits electrophysiology discussion; catheter ablation is potentially curative.

Key red flags

Life-threatening adverse features

Shock, syncope with severe/ongoing hypotension, myocardial ischaemia, severe heart failure with pulmonary oedema, or immediately post-ROSC.

Regular broad-complex tachycardia

Assume VT unless an expert/known prior ECG securely establishes SVT with aberrancy. AV dissociation, capture/fusion beats or extreme axis support VT but their absence does not prove SVT.

Irregular broad-complex tachycardia

Consider pre-excited AF or polymorphic VT. Varying QRS shape with very short R-R intervals in WPW is particularly dangerous; avoid AV-nodal blockers.

Investigation priorities

01
ABCDE, ECG/BP/SpO2 monitoring, IV access and defibrillator availabilityFirst step

Identify instability and make deterioration immediately treatable.

Management branches

UnstableTachyarrhythmia with life-threatening features

Adverse features attributable to SVT/tachyarrhythmia.

  1. Call expert/resuscitation help, attach pads, treat reversible causes and prepare careful sedation/anaesthesia if conscious without delaying shock.
  2. Deliver synchronised cardioversion: RCUK initial 70-120 J for atrial flutter or paroxysmal SVT, with stepwise energy increases and up to three attempts.
  3. If unsuccessful and instability persists, the RCUK pathway uses either procainamide 10–15 mg/kg IV (maximum 1 g) over 20 minutes or amiodarone 300 mg IV over 10–20 minutes, selected for rhythm, contraindications and product availability; then repeat synchronised cardioversion.
  4. If the patient becomes pulseless, switch immediately to the cardiac-arrest algorithm; do not continue synchronised shocks.
Stable narrow regularVagal manoeuvre then adenosine

Regular QRS below 120 ms without life-threatening features and no evidence of pre-excitation.

  1. Record a 12-lead and start a continuous rhythm strip. Perform a modified Valsalva if safe: semi-recumbent 40 mmHg strain for 15 seconds, immediately lie flat and passively raise legs to 45 degrees for 15 seconds, then return semi-recumbent and assess at 1 minute; the REVERT trial permitted a repeat attempt.

Key medicines

Adenosine—RCUK March 2026 algorithm regimen6 mg rapid IV bolus with an immediate rapid saline flush; if unsuccessful, 12 mg rapid IV; if still unsuccessful, 18 mg rapid IV. RCUK does not mandate a fixed inter-dose interval on the algorithm: assess the immediate response and maintain continuous ECG.Use in hospital with continuous ECG/BP and cardiorespiratory resuscitation equipment. Do not use for irregular broad tachycardia/pre-excited AF. Avoid in sick-sinus or second/third-degree AV block without a pacemaker, bronchospastic asthma/COPD, severe hypotension, decompensated heart failure and long-QT syndrome. Heart transplant/dipyridamole heighten effect; caffeine/theophylline antagonise it. The 18 mg step exceeds the cited UK SmPC maximum.
Adenosine—product-label comparison3 mg rapid IV bolus over 2 seconds; if SVT persists after 1-2 minutes, 6 mg rapid IV; if it persists after a further 1-2 minutes, 12 mg rapid IV. The cited SmPC says additional or higher doses are not recommended.The current RCUK 6–12–18 mg sequence remains the national peri-arrest algorithm. State the chosen preparation and authority explicitly, and resolve the out-of-label 18 mg step through organisational medicines governance.
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Sources and review status7 sources · checked 25 Aug 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 25 Aug 2026; clinical approval remains outstanding.

  • RCUK Adult tachyarrhythmia algorithm V3 March 2026
  • RCUK 2025 Adult Advanced Life Support
  • Adenosine 3 mg/mL UK SmPCLicensed 3-6-12 mg schedule and contraindications; explicitly differs from current RCUK.
  • Verapamil injection SmPC
  • Atenolol injection SmPC
  • REVERT randomised trialPrimary trial for the modified Valsalva technique.
  • 2019 ESC SVT guideline landing pageMechanism-specific long-term context where no NICE SVT guideline exists.

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateRapid draftClinical stateAwaiting reviewJurisdictionUnited Kingdom
If unsuccessful, follow the current RCUK algorithm: adenosine 6 mg rapid IV bolus with immediate flush; if unsuccessful give 12 mg; if still unsuccessful give 18 mg. Warn the patient about brief flushing, chest discomfort and dyspnoea and record ECG through each dose.
  • Use the current RCUK 6–12–18 mg sequence as the national peri-arrest algorithm. The cited UK SmPC instead licenses 3 mg over 2 seconds, then 6 mg after 1–2 minutes, then 12 mg after another 1–2 minutes and says no higher dose; the RCUK 18 mg step is therefore outside that product label and must be reconciled through organisational medicines governance.
  • If adenosine is contraindicated or fails, seek expert help and choose verapamil OR a beta-blocker according to EF, BP, conduction, airway disease, interacting drugs and diagnostic certainty; these are conditional alternatives, not an automatic sequence.
  • If drug therapy fails or the patient deteriorates, use synchronised cardioversion.