Supraventricular Tachycardia (SVT) Management

Definition

SVT is an umbrella term for tachycardias (rate >100 bpm at rest) whose mechanism involves tissue from the His bundle or above. It includes AVNRT, AVRT, focal AT, MAT, atrial flutter, IST, and junctional tachycardia. For guideline purposes, AF is excluded. PSVT (paroxysmal SVT) is a subset characterized by abrupt onset and termination, typically AVNRT or AVRT. SVT prevalence is 2.29/1,000; PSVT incidence ~36/100,000/year with ~570,000 affected in the US. sources/svt-aha-2015 (rating: very high)

Key Concepts

Epidemiology

• SVT prevalence 2.29 per 1,000 persons; ~89,000 new PSVT cases/year in the US sources/svt-aha-2015 (rating: very high)
• Women have 2× the risk of PSVT vs men; >65 years have >5× the risk of younger patients
• AVNRT >60% female; AVRT more prevalent in younger patients; pre-excitation prevalence 0.1–0.3%
• Emergency department visits ~50,000/year for SVT; rarely primary reason for hospital admission

Acute Management Framework

1. Vagal maneuvers (Class I/B-R — AHA 2015; I/B — ESC 2019): Valsalva (bear down 10–30 sec, ≥30–40 mmHg); carotid sinus massage after auscultating for bruit; overall success 27.7% when combined. Modified Valsalva (ESC 2019 evidence): semi-recumbent strain → supine repositioning + passive leg raise → 43% conversion vs 17% conventional (Appelboam et al. 2015 RCT). First-line for all regular SVT. sources/svt-aha-2015 sources/svt-esc-2019 (both very high)
2. Adenosine (Class I/B-R — AHA 2015; I/B — ESC 2019): 6–18 mg rapid IV bolus; requires proximal IV + saline flush; success >90% for AVNRT/AVRT; also diagnostic (unmasks flutter/AT); short half-life limits side effects. Mean termination dose ~6 mg; repeat at 12 mg, then 18 mg. Avoid if pre-excitation on resting ECG (can precipitate rapidly conducted AF → VF). Caution in severe asthma (verapamil preferred). sources/svt-aha-2015 sources/svt-esc-2019
3. IV diltiazem or verapamil (Class IIa/B-R — both guidelines): Terminates SVT in 64–98%; hemodynamically stable patients only; NEVER if VT suspected, pre-excited AF, or systolic HF/hypotension. Verapamil 0.075–0.15 mg/kg IV over 2 min; diltiazem 0.25 mg/kg IV over 2 min. sources/svt-aha-2015 sources/svt-esc-2019
4. IV beta blockers (Class IIa/C — both guidelines): Reasonable if above ineffective; excellent safety profile; more effective at rate control than termination; contraindicated in decompensated HF
5. Synchronized cardioversion (Class I/B — both guidelines): If hemodynamically unstable OR if pharmacotherapy fails/contraindicated in stable patients

Ongoing Management

• Catheter ablation (Class I/B-NR): Preferred first-line definitive therapy for symptomatic SVT; provides potential cure without chronic drug therapy; large registries show >95% success for AVNRT/AVRT with <1% AV block risk sources/svt-aha-2015
• AV nodal blockers (Class I/B-R): Oral beta blockers, diltiazem, or verapamil — appropriate when patient prefers non-ablation or has no access to electrophysiologist
• Class IC agents (Class IIa/B-R): Flecainide or propafenone — effective (86–93% freedom from recurrence at 12 months) but contraindicated in structural/ischemic heart disease; proarrhythmic
• Sotalol (IIb/B-R), dofetilide (IIb/B-R), amiodarone (IIb/C-LD), digoxin (IIb/C-LD): Reserved for patients not candidates for ablation and in whom preferred agents are ineffective/contraindicated
• Patient education on self-performed vagal maneuvers (Class I/C-LD)

ECG Differential Diagnosis of Narrow QRS SVT

• Irregular: AF, MAT, atrial flutter with variable AV block
• Regular, short RP (<90 ms): AVNRT (pseudo-S inferior, pseudo-R' V1), orthodromic AVRT (P in early ST segment)
• Regular, long RP: AT (P after T wave), atypical AVNRT (fast-slow), PJRT (slowly conducting AP)
• If atrial rate > ventricular rate: flutter or AT (rare 2:1 AVNRT)
• Junctional tachycardia: AV dissociation with isorhythmic pattern may be present

ECG Differentiation of Wide Complex Tachycardia

• AV dissociation or fusion beats = diagnostic of VT
• Precordial concordance (all positive or all negative) = VT
• Brugada criteria: absence of any R-S in V1–V6, or R-S interval >100 ms in any precordial lead = VT
• Vereckei (aVR): initial R wave, initial R or Q >40 ms, notch on descending limb of negative QRS = VT
• R-wave peak time in lead II ≥50 ms = VT
• QRS in tachycardia identical to sinus rhythm = SVT
• Default assumption: if uncertain, treat as VT — verapamil/diltiazem in VT = potentially lethal sources/svt-aha-2015

Critical Safety Principle — Pre-Excited AF

• CLASS III/HARM: IV digoxin, amiodarone, beta-blockers, diltiazem, and verapamil in pre-excited AF
• These agents block/slow the AV node, increase catecholamines via hypotension, and may enhance or lose competitive concealment of the accessory pathway → accelerate accessory pathway conduction during AF → ventricular rate >300 bpm → VF
• Digoxin additionally shortens accessory pathway refractoriness directly
• Correct treatment of pre-excited AF: Direct current cardioversion (if hemodynamically unstable, Class I) or IV ibutilide/procainamide (if stable, Class I/C-LD) sources/svt-aha-2015

Drug Selection by Scenario

ESC 2019 vs AHA 2015 — Key Differences

PROCAMIO trial (ESC 2019 key new evidence): In haemodynamically stable wide QRS tachycardia (VT or SVT with BBB), IV procainamide was associated with fewer major cardiac adverse events and higher 40-minute termination rate than IV amiodarone. This data downgraded IV amiodarone in wide QRS management from Class I (2003) to IIb/B (2019). sources/svt-esc-2019

Contradictions / Open Questions

• Optimal strategy for minimally symptomatic AVNRT: ablation vs. observation — both AHA 2015 and ESC 2019 support observation for minimally symptomatic patients; ESC 2019 explicitly recommends "abstinence from therapy" as IIa/C sources/svt-aha-2015 sources/svt-esc-2019
• Non-CTI-dependent atrial flutter: no RCTs comparing ablation vs antiarrhythmic drugs; ablation outcomes variable (73–100% success, 7–53% recurrence)
• Post-AF ablation flutter: defer repeat ablation to 3-month waiting period unless pharmacotherapy fails
• Adenosine in WPW: can precipitate AF which may rapidly conduct over the accessory pathway; cardioversion must be immediately available — both guidelines concur; ESC 2019 explicitly adds this as a caveat to adenosine IIa recommendation in wide QRS management
• Anticoagulation threshold for isolated atrial flutter without AF: ESC 2019 acknowledges CHA₂DS₂-VASc not validated in isolated flutter; initiates as IIa/C (threshold "not established") — creates uncertainty vs AHA 2015 approach mirroring AF sources/svt-esc-2019

Connections

• Related to concepts/AVNRT
• Related to concepts/AVRT-Accessory-Pathway
• Related to concepts/Inappropriate-Sinus-Tachycardia
• Related to entities/Atrial-Flutter
• Related to concepts/Wide-Complex-Tachycardia
• Related to concepts/Antiarrhythmic-Drugs
• Related to entities/Atrial-Fibrillation (pre-excited AF; anticoagulation for flutter mirrors AF)

Sources

• sources/svt-aha-2015
• sources/svt-esc-2019