What is the definition of supraventricular (above the ventricles) arrhythmia?

Definition of Supraventricular Arrhythmia

Supraventricular arrhythmia 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

Anatomical Origin

Supraventricular arrhythmias are characterized by their origin point in the cardiac conduction system:

• They originate in tissue at or above the bundle of His
• Include rhythms from:
  • Sinus node
  • Atrial tissue (including atrial flutter)
  • Junctional tissue
  • Accessory pathways

Types of Supraventricular Arrhythmias

The term "supraventricular arrhythmia" encompasses several distinct types:

1. Atrioventricular Nodal Reentrant Tachycardia (AVNRT) - Most common type in adults, involving dual pathways within the AV node 1

2. Atrioventricular Reentrant Tachycardia (AVRT) - Involves an accessory pathway between atria and ventricles 1

3. Atrial Tachycardia (AT) - Originates from a focal source in the atria 1

4. Atrial Flutter - Macro-reentrant circuit in the atrium, typically around anatomical obstacles 1

5. Focal Junctional Tachycardia - Originates from the AV node or His bundle 1

Distinguishing Features

It's important to note that while "supraventricular arrhythmia" is a broad term encompassing all arrhythmias originating above the ventricles (excluding atrial fibrillation), the term "supraventricular tachycardia" (SVT) is more specific and includes only AVNRT, AVRT, and AT 1.

The ECG features of supraventricular arrhythmias typically include:

• Narrow QRS complexes (unless there is aberrant conduction)
• Heart rates that vary depending on the specific type:
  • For focal junctional tachycardia: 110-250 bpm 1
  • For paroxysmal SVT: often 150-250 bpm 2, 3

Mechanisms

Supraventricular arrhythmias occur through several mechanisms:

• Reentry - Most common mechanism, involving a circuit with unidirectional block and slow conduction 1
• Enhanced automaticity - Cells spontaneously depolarize at an accelerated rate 1
• Triggered activity - Afterdepolarizations that reach threshold and trigger new action potentials 1

Clinical Significance

Supraventricular arrhythmias are:

• Relatively common (prevalence of PSVT: 2.25 per 1000) 1
• Often repetitive
• Occasionally persistent
• Rarely life-threatening 1

They can cause significant symptoms including palpitations, lightheadedness, chest discomfort, dyspnea, and occasionally syncope, which may impact quality of life 2, 3, 4.

Important Distinction

A key distinction in terminology noted in the ACC/AHA/ESC guidelines is that "supraventricular arrhythmia" refers to all types of supraventricular arrhythmias excluding atrial fibrillation, while "SVT" specifically includes AVNRT, AVRT, and AT 1.