Supraventricular Arrhythmias (SVT, Flutter)

Supraventricular arrhythmias are tachyarrhythmias that originate at or above the atrioventricular node, requiring atrial or junctional tissue for their initiation or maintenance. They include atrioventricular nodal re-entrant tachycardia, atrioventricular re-entrant tachycardia (as in Wolff-Parkinson-White syndrome), atrial tachycardia, and atrial flutter. This entry orients the reader to their mechanisms and clinical features as a reference topic.

Definition

Supraventricular tachycardias are rapid heart rhythms that depend on tissue at or above the bundle of His for initiation and maintenance, typically producing a narrow-complex tachycardia; atrial flutter is an organized atrial re-entrant arrhythmia, classically with a sawtooth flutter-wave pattern.

Scope

The entry covers the family of regular and organized supraventricular tachycardias and atrial flutter, their re-entrant and automatic mechanisms, the electrocardiographic clues that distinguish them, and the role of the atrioventricular node as both a conduit and a participant. Atrial fibrillation, technically supraventricular, is treated in its own entry. The content is descriptive and educational.

Key concepts

• Narrow-complex tachycardia
• Atrioventricular nodal re-entrant tachycardia (AVNRT)
• Atrioventricular re-entrant tachycardia (AVRT) and accessory pathways
• Wolff-Parkinson-White pre-excitation (delta wave)
• Atrial flutter and the cavotricuspid isthmus
• Re-entry versus enhanced automaticity
• Vagal maneuvers and AV-nodal dependence

Mechanisms

Most paroxysmal supraventricular tachycardias are re-entrant. In atrioventricular nodal re-entrant tachycardia, a circuit forms within or near the atrioventricular node using functionally distinct fast and slow pathways. In atrioventricular re-entrant tachycardia, an accessory pathway connecting atrium and ventricle (as in Wolff-Parkinson-White syndrome) completes a macro-re-entrant loop; antegrade conduction over such a pathway produces the delta wave of ventricular pre-excitation. Atrial flutter is a macro-re-entrant atrial circuit, most commonly around the cavotricuspid isthmus, generating regular flutter waves. Because many of these circuits traverse or depend on the atrioventricular node, transiently blocking nodal conduction can terminate or unmask them (Brugada et al., 2019).

Clinical relevance

Supraventricular arrhythmias commonly present with palpitations, and recognizing their patterns is central to evaluating regular narrow-complex tachycardias; pre-excitation syndromes additionally carry implications for rare but serious rhythm risk. This entry presents the concepts and evidence framework for educational reference and is not a basis for individual diagnosis or treatment.

Epidemiology

Paroxysmal supraventricular tachycardia is a frequent cause of palpitations across all ages, with atrioventricular nodal re-entrant tachycardia the most common mechanism in adults; atrial flutter often coexists with atrial fibrillation and shares its risk factors and thromboembolic concerns.

Evidence & guidelines

The ESC (Brugada et al., 2019) and ACC/AHA/HRS (Page et al., 2016) guidelines provide the contemporary diagnostic and management framework, including the central role of catheter ablation, which can be curative for many re-entrant supraventricular tachycardias by interrupting the responsible circuit.

History

The 1930 description by Wolff, Parkinson, and White of a short PR interval with bundle-branch-block morphology in young people prone to tachycardia identified the pre-excitation syndrome that bears their names and pointed toward accessory pathways. The later elucidation of re-entry and the advent of catheter ablation transformed these arrhythmias into frequently curable conditions.

Seminal works

• wolff-parkinson-white-1930
• brugada-2019

Frequently asked questions

Why do vagal maneuvers sometimes stop a supraventricular tachycardia?

Many supraventricular tachycardias depend on conduction through the atrioventricular node; vagal maneuvers transiently slow nodal conduction, which can break the re-entrant circuit and terminate the arrhythmia or help reveal the underlying rhythm.

What is a delta wave?

A delta wave is a slurred upstroke at the start of the QRS complex seen when an accessory pathway conducts the impulse to the ventricle early (pre-excitation), characteristic of Wolff-Parkinson-White pattern.