Pharmacology · Cardiovascular

Supraventricular Tachycardia: Classification, Management, and Catheter Ablation

Classification, adenosine as diagnostic tool, Wolff-Parkinson-White emergency, wide-complex tachycardia, and ablation outcomes

Adenosine response is the key classification tool: it terminates atrioventricular nodal-dependent tachycardias (AVNRT and AVRT, which require the atrioventricular node as an obligate circuit limb) and only transiently slows atrial tachycardias (atrial flutter, focal atrial tachycardia) whose circuits originate entirely in atrial tissue — this dual role is both therapeutic and diagnostic.
Wolff-Parkinson-White with pre-excited atrial fibrillation is a medical emergency: all nodal-blocking agents (adenosine, verapamil, diltiazem, digoxin, beta-blockers) are absolutely contraindicated because they redirect all conduction through the accessory pathway, enabling atrial fibrillation at 200–300+ beats per minute and risking ventricular fibrillation; treatment is IV procainamide, IV ibutilide, or immediate synchronized cardioversion.
Wide-complex tachycardia must be treated as ventricular tachycardia until proven otherwise — ventricular tachycardia accounts for 80% of cases overall and over 90% in structural heart disease; verapamil is absolutely contraindicated in uncertain wide-complex tachycardia; procainamide, amiodarone, and direct-current cardioversion are safe for both ventricular tachycardia and SVT with aberrancy.
Catheter ablation success rates vary by substrate: AVNRT slow pathway modification achieves over 95% cure with cryoablation reducing complete heart block risk to below 0.1%; cavotricuspid isthmus ablation for typical atrial flutter achieves 95–97% acute success, the highest of any ablation procedure; pulmonary vein isolation for paroxysmal atrial fibrillation achieves 60–80% at one year for a single procedure, rising to 75–90% with repeat procedures.
Ablation is now first-line for atrial fibrillation with heart failure with reduced ejection fraction (CASTLE-AF demonstrated mortality and hospitalization benefit over rate control), and is preferred over lifelong antiarrhythmic drug therapy for symptomatic Wolff-Parkinson-White — drugs cannot reliably prevent sudden death from pre-excited atrial fibrillation, but ablation eliminates the accessory pathway entirely.

Supraventricular Tachycardia Classification and Adenosine Response

Atrioventricular Nodal-Dependent

Atrioventricular Nodal Reentrant Tachycardia / Atrioventricular Reentrant Tachycardia

Re-entrant circuit requires atrioventricular node as obligate limb
Adenosine TERMINATES — confirms atrioventricular nodal dependence
Atrioventricular nodal reentrant tachycardia: re-entry within atrioventricular node; pseudo-R prime in V1; most common (60%)
Atrioventricular reentrant tachycardia: accessory pathway circuit; Wolff-Parkinson-White; delta wave in sinus rhythm
Acute management: vagal maneuvers first; adenosine; verapamil or diltiazem second-line
Ablation curative: atrioventricular nodal reentrant tachycardia over 95%; atrioventricular reentrant tachycardia 93 to 95%

Atrial Origin

Atrial Flutter / Focal Atrial Tachycardia

Circuit does NOT require atrioventricular node — originates entirely in atria
Adenosine SLOWS rate but does not terminate — atrial circuit continues
Atrial flutter: sawtooth pattern; 300 bpm atrial rate; 150 bpm ventricular rate (2:1 block); harder to rate-control than atrial fibrillation
Focal atrial tachycardia: discrete atrial focus; morphologically distinct P wave; automatic or triggered mechanism
Ibutilide most effective pharmacologic cardioversion for atrial flutter
Cavotricuspid isthmus ablation curative for typical atrial flutter (over 95%)

Critical Safety Rules

Wolff-Parkinson-White Emergency

Pre-Excited Atrial Fibrillation

Accessory pathway conducts atrial fibrillation at 200 to 300+ beats per minute — risk of ventricular fibrillation
Electrocardiogram: irregularly irregular, wide and variable QRS, very rapid rate
CONTRAINDICATED: adenosine, verapamil, diltiazem, digoxin, beta-blockers — all accelerate accessory pathway conduction
CORRECT TREATMENT: intravenous procainamide (blocks accessory pathway directly) or intravenous ibutilide
Hemodynamically unstable: immediate synchronized direct-current cardioversion
Definitive cure: catheter ablation of the accessory pathway

Wide-Complex Tachycardia

Treat as Ventricular Tachycardia Until Proven Otherwise

Ventricular tachycardia accounts for 80% of wide-complex tachycardia (over 90% in structural heart disease)
Electrocardiogram features confirming ventricular tachycardia: atrioventricular dissociation; fusion beats; capture beats; northwest axis
NEVER give verapamil — causes collapse in ventricular tachycardia; causes ventricular fibrillation in pre-excited atrial fibrillation
Safe for both ventricular tachycardia and supraventricular tachycardia with aberrancy: procainamide, amiodarone, direct-current cardioversion
Confirmed supraventricular tachycardia with aberrancy: adenosine, verapamil, diltiazem acceptable

Catheter Ablation — Outcomes by Arrhythmia Type

Arrhythmia	Procedure	Acute Success	Key Points
Atrioventricular nodal reentrant tachycardia	Slow pathway modification (radiofrequency or cryo)	Over 95%; recurrence 1 to 3%	Class I guideline; cryoablation reduces complete atrioventricular block risk to below 0.1%; radiofrequency risk 0.5 to 1%
Atrioventricular reentrant tachycardia / Wolff-Parkinson-White	Accessory pathway ablation	93 to 95% overall; higher for left free wall pathways	Class I for symptomatic Wolff-Parkinson-White; eliminates pre-excited atrial fibrillation risk; drugs cannot reliably achieve this
Typical atrial flutter	Cavotricuspid isthmus ablation	95 to 97%; 90 to 95% at one year	Highest success rate of any ablation procedure; Class I for symptomatic typical flutter; rate control pharmacologically difficult
Paroxysmal atrial fibrillation	Pulmonary vein isolation	60 to 80% at one year (single procedure)	Repeat procedures: 75 to 90%; persistent atrial fibrillation lower (40 to 60%); first-line in atrial fibrillation with heart failure with reduced ejection fraction (CASTLE-AF)

The Adenosine Rule and the Verapamil Rule

Adenosine terminates atrioventricular nodal-dependent tachycardias (atrioventricular nodal reentrant tachycardia, atrioventricular reentrant tachycardia) and slows but does not terminate atrial tachycardias (flutter, focal atrial tachycardia, atrial fibrillation) — this response is both therapeutic and diagnostic. Verapamil is contraindicated in any wide-complex tachycardia of uncertain origin: it causes cardiovascular collapse in ventricular tachycardia and can precipitate ventricular fibrillation in pre-excited atrial fibrillation. Treat wide-complex tachycardia as ventricular tachycardia until proven otherwise.

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