What is the definition of supraventricular (SV) arrhythmia?

Definition of Supraventricular Arrhythmia

Supraventricular arrhythmia (SVA) refers to all types of abnormal heart rhythms that originate from or above the atrioventricular node and His bundle, including rhythms emanating from the sinus node, atrial tissue, junctional tissue, and those involving accessory pathway-mediated tachycardia, but excluding atrial fibrillation. 1

Types of Supraventricular Arrhythmias

Supraventricular arrhythmias encompass several distinct types:

1. Sinus node arrhythmias

   • Sinus tachycardia (non-paroxysmal, gradual onset and termination)
   • Sinus node dysfunction

2. Atrial arrhythmias

   • Atrial tachycardia (AT)
   • Atrial flutter
   • Multifocal atrial tachycardia (MAT)

3. Junctional arrhythmias

   • Focal junctional tachycardia
   • Nonparoxysmal junctional tachycardia

4. Atrioventricular nodal and accessory pathway arrhythmias

   • Atrioventricular nodal reentrant tachycardia (AVNRT)
   • Atrioventricular reentrant tachycardia (AVRT)

Electrophysiological Characteristics

Supraventricular arrhythmias typically present with:

• Heart rates ranging from 100-250 beats per minute (varies by type)
• Narrow QRS complexes (unless there is pre-existing bundle branch block or aberrant conduction)
• Regular or irregular rhythm depending on the specific arrhythmia
• May show AV dissociation in certain types (e.g., focal junctional tachycardia)

Mechanisms

The primary mechanisms of SVAs include:

• Re-entry: Most common mechanism in AVNRT and AVRT, involving a fixed circuit with unidirectional block and slow conduction
• Enhanced automaticity: Common in focal atrial and junctional tachycardias
• Triggered activity: Seen in certain forms of atrial tachycardia and junctional tachycardia 1

Clinical Significance

SVAs are:

• Relatively common in the general population
• Often repetitive
• Occasionally persistent
• Rarely life-threatening (except in cases with pre-excitation syndromes like WPW with AF)

The estimated prevalence of paroxysmal SVT is approximately 2.25 per 1,000 persons, with an incidence of 35 per 100,000 person-years 1.

Epidemiology

• More common in females (twofold greater relative risk compared to males)
• Age of onset varies by type:
  • AVNRT: typically presents around 32 ± 18 years
  • AVRT: typically presents around 23 ± 14 years
• Atrial flutter is 2.5 times more common in men than women 1

Important Distinction

It's important to note that while "supraventricular arrhythmia" (SVA) refers to all types of supraventricular arrhythmias excluding atrial fibrillation, the term "supraventricular tachycardia" (SVT) specifically includes AVNRT, AVRT, and atrial tachycardia 1, 2.

Clinical Caveat

When evaluating a patient with a wide QRS tachycardia, it should be treated as ventricular tachycardia until proven to be SVT with aberration, as misdiagnosis could lead to inappropriate treatment and potentially adverse outcomes 3.