What is Supraventricular Tachycardia (SVT)?

Introduction

Supraventricular tachycardia (SVT) is a rapid heart rhythm that originates above the ventricles in the atria or AV node. It leads to episodes of sudden-onset rapid heart rate, often exceeding 100 beats per minute, and sometimes reaching 150-250 beats per minute.

Causes

SVT is usually caused by abnormal electrical circuits in the heart's conduction system. Common mechanisms include:

  1. Atrioventricular nodal reentrant tachycardia (AVNRT) – The most common type, involving dual pathways within the AV node.
  2. Atrioventricular reciprocating tachycardia (AVRT) – Related to conditions like Wolff-Parkinson-White (WPW) syndrome, where an extra pathway creates a re-entry circuit.
  3. Atrial tachycardia – Abnormal ectopic electrical focus in the atria causing rapid firing.

Symptoms

Symptoms vary depending on the severity and duration of SVT but commonly include: - Palpitations (rapid heartbeats) - Dizziness or lightheadedness - Shortness of breath - Chest discomfort - Anxiety - Syncope (in rare cases)

Diagnosis

Diagnosis is made using: - Electrocardiogram (ECG) – Shows characteristic narrow QRS tachycardia. - Holter monitor – For intermittent episodes. - Electrophysiological studies (EPS) – For identifying specific pathways in recurrent or difficult cases.

Treatment

Acute Episode Management

  • Vagal maneuvers – Such as the Valsalva maneuver or carotid sinus massage.
  • Adenosine – First-line medication for SVT termination.
  • Beta-blockers or calcium channel blockers – Used when adenosine is ineffective.

Long-term Management

  • Medications – Beta-blockers or antiarrhythmics for frequent episodes.
  • Catheter ablation – Recommended for recurrent or symptomatic cases by destroying the abnormal pathway.
  • Lifestyle modifications – Avoiding triggers such as excessive caffeine, alcohol, and stress.

Conclusion

SVT is a generally non-life-threatening arrhythmia, but it can significantly impact quality of life. With proper diagnosis and treatment, most patients can manage their condition effectively.

Source recommendations

1. 2023 AHA/ACC/HRS Guideline for the Evaluation and Management of Patients With Cardiac Arrhythmias

  1. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001193
  2. https://www.hrsonline.org/guidance/clinical-resources
  3. https://www.ahajournals.org/doi/10.1161/cir.0000000000000499
  4. https://www.jacc.org/doi/10.1016/j.jacc.2023.08.017
  5. https://www.heartrhythmjournal.com/article/S1547-5271(23)02246-4/fulltext

2. 2020 ESC Guidelines for the Diagnosis and Management of Atrial Fibrillation

  1. https://academic.oup.com/eurheartj/article/42/5/373/5899003
  2. https://pubmed.ncbi.nlm.nih.gov/32860505/
  3. https://www.escardio.org/static-file/Escardio/Guidelines/Documents/ehaa612.pdf
  4. https://www.ahajournals.org/doi/10.1161/CIR.0000000000001193
  5. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Atrial-Fibrillation

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