What is supraventricular tachycardia (SVT)?

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What is Supraventricular Tachycardia (SVT)?

Supraventricular tachycardia (SVT) is an umbrella term for abnormally rapid heart rhythms (exceeding 100 beats per minute at rest) that originate from or involve tissue at or above the bundle of His, characterized by sudden onset and termination, with rates typically between 150-300 beats per minute. 1

Core Definition and Mechanism

SVT encompasses multiple specific arrhythmias including:

  • Atrioventricular nodal reentrant tachycardia (AVNRT) - the most common type 1
  • Atrioventricular reciprocating tachycardia (AVRT) - involving accessory pathways 1
  • Atrial tachycardia (AT) - including focal and multifocal variants 1
  • Macroreentrant atrial tachycardia - including typical atrial flutter 1
  • Junctional tachycardia 1

The term specifically excludes atrial fibrillation and sinus tachycardia. 1 The mechanism involves either an extra electrical pathway or a reentrant loop in the heart's conduction system that allows electrical signals to circle repeatedly, causing rapid heart rates. 2

Clinical Presentation

Typical Symptoms

Patients with SVT commonly experience:

  • Palpitations (86% of patients) 3
  • Chest discomfort or pressure (47% of patients) 3
  • Dyspnea/shortness of breath (38% of patients) 3, 2
  • Fatigue or weakness 2
  • Lightheadedness or dizziness 4
  • Syncope (approximately 15% of patients, particularly at onset or with prolonged pause after termination) 5, 2

Characteristic Features

The rhythm is extremely regular after the first 10-20 beats, like a metronome, with rates typically 260-300 beats per minute in infants and 150-300 beats per minute in adults. 1, 2 The episodes have abrupt onset and termination, distinguishing them from sinus tachycardia which gradually accelerates and decelerates. 1

Epidemiology

Prevalence and Incidence

  • Estimated prevalence is 2.25 per 1,000 population 1
  • Incidence is 35 per 100,000 person-years 1
  • Affects 168 to 332 per 100,000 individuals 3

Age and Gender Distribution

  • Mean age at onset is 57 years (ranging from infancy to over 90 years) 1
  • Women have twice the risk compared to men (relative risk 2.0) 1
  • Approximately 50% of patients are aged 45-64 years 3
  • 67.5% of patients are female 3

Patients with "lone" SVT (no structural heart disease) are younger (mean age 37 years) compared to those with other cardiovascular disease (mean age 69 years). 1

Structural Basis

Most people with SVT have structurally normal hearts—the problem lies in the electrical system, not the heart muscle itself. 2 The arrhythmia results from abnormal electrical pathways or reentrant circuits in the atria or atrioventricular node. 6

Key Distinguishing Features from Other Arrhythmias

When compared to sinus tachycardia, SVT demonstrates:

  • Heart rate almost always exceeds 230 beats per minute in infants (sinus tachycardia is typically below 230) 1
  • Extreme regularity of R-R intervals after initial beats 1
  • P waves visible in only 60% of cases, with morphology different from sinus P waves 1
  • QRS complex typically identical to sinus rhythm (aberration is rare in infants, occurring in only 3% of cases) 1

Potential Complications

While generally benign, untreated SVT can cause serious complications:

  • Tachycardia-mediated cardiomyopathy (1% of patients) when SVT persists for weeks to months 5, 3
  • Heart failure from persistent rapid ventricular response 5
  • Pulmonary edema from increased atrial pressures 5
  • Myocardial ischemia from increased oxygen demand and decreased coronary perfusion time 5
  • Stroke risk, particularly in adults with congenital heart disease 5

Patients with accessory pathways (Wolff-Parkinson-White syndrome) who develop atrial fibrillation face risk of extremely rapid ventricular rates that can degenerate into ventricular fibrillation. 5, 2

Diagnostic Approach

Diagnosis requires capturing the rhythm on ECG during an episode to confirm SVT and determine the specific type. 2 Extended cardiac monitoring with Holter monitors or event recorders may be necessary if episodes are infrequent. 4 An echocardiogram should be performed to exclude underlying structural heart disease. 2

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

2
Guideline

Understanding and Managing Supraventricular Tachycardia (SVT)

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

5
Guideline

Complications of Supraventricular Tachycardia

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2026

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Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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