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Understanding Supraventricular Tachycardia

May 27, 2025

Lecture on Supraventricular Tachycardia (SVT)

Introduction

  • Presenter: Tom from zero2finals.com
  • Focus: Understanding SVT for exam preparation (not clinical practice guidance)
  • Important to consult guidelines and experienced seniors in clinical practice.

Definition

  • Supraventricular Tachycardia (SVT): A fast heart rate caused by abnormal electrical signals originating above the ventricles, typically in the atria.

Pathophysiology

  • Normal Heart Signal Pathway:
    • Starts in the sinoatrial (SA) node, located at the junction of the superior vena cava and right atrium.
    • Travels through the atria causing contraction, then through atrioventricular (AV) node to ventricles causing contraction.
  • Abnormal Pathway in SVT:
    • Signal re-enters atria from ventricles, causing a loop and fast tachycardia.
    • Results in paroxysmal SVT (recurrent episodes with normal rhythm periods).

ECG Characteristics

  • Narrow Complex Tachycardia: QRS complex < 0.12 seconds (3 small squares on ECG)
  • SVT appearance on ECG:
    • QRS complex followed by T wave repetitively.

Differential Diagnoses

  • Sinus Tachycardia: Normal P wave, QRS, T wave; response to underlying issues like sepsis, pain.
  • Atrial Fibrillation: Irregularly irregular QRS complexes.
  • Atrial Flutter: Atrial rate ~300 bpm, sawtooth ECG pattern, regular QRS intervals.
  • SVT with Bundle Branch Block: May cause broad complex tachycardia.

Types of SVT

  • Atrioventricular Nodal Reentrant Tachycardia (AVNRT): Re-entry through AV node.
  • Atrioventricular Reentrant Tachycardia (AVRT):
    • Involves an accessory pathway.
    • Commonly seen in Wolf-Parkinson-White Syndrome (extra pathway in heart).
  • Atrial Tachycardia: Originates from atria outside SA node.

Acute Management in Stable Patients

  • Stepwise Approach:
    • Valsalva maneuver (blow against resistance).
    • Carotid sinus massage.
    • Adenosine (if simple measures fail).
    • Alternatives: Verapamil (if adenosine contraindicated).
  • Adenosine:
    • Slows conduction through AV node, resetting rhythm.
    • Fast IV bolus; can cause brief asystole or bradycardia.
    • Contraindications: asthma, COPD, heart failure, heart block, hypotension.

Management in Unstable Patients

  • Criteria: Respiratory distress, chest pain, hypotension, heart failure.
  • Treatment: Synchronized cardioversion with a defibrillator, possibly amiodarone.

Long-term Management

  • Recurrent SVT Management:
    • Medications: Beta blockers, calcium channel blockers, amiodarone.
    • Radiofrequency ablation.
  • Radiofrequency Ablation:
    • Done in cath lab; locates and ablates abnormal pathways.
    • Can be curative for SVT, WPW syndrome, atrial flutter, and fibrillation.

Conclusion

  • Information and resources available on zero2finals.com.
  • Additional educational content through various platforms linked in the video description.

Note: For actual clinical practice, always refer to current guidelines and consult with experienced professionals.

Full transcript