Paroxysmal supraventricular tachycardia

SVT terminology can be confusing, as some references consider SVT to be any rhythm originating above the ventricles (i.e. sinus tachycardia, MAT, atrial flutter, atrial fibrillation, PSVT, etc). As these entities have their own specific articles and treatment, only paroxysmal supraventricular tachycardia links here.

Background

• Also known as PSVT and frequently referred to just as SVT
• AV nodal reentrant tachycardia (AVNRT) and AV reentrant tachycardia (AVRT) are subtypes of PSVT
• Most common dysrhythmia in children
• Infants: poor feeding, tachypnea, and irritability

Clinical Presentation

• Palpitations
• May also present with haemodynamic instability if severe, eg hypotension, syncope

Differential Diagnosis

Palpitations

• Arrhythmias:
  • Narrow-complex tachycardias
  • Wide-complex tachycardias
  • AV blocks
    • Second Degree AV Block Type I (Wenckeback)
    • Second Degree AV Block Type II
    • Third Degree AV Block
  • Premature atrial contraction
  • Premature junctional contraction
  • Premature ventricular contraction
  • Sick sinus syndrome
  • Wandering atrial pacemaker
• Non-arrhythmic cardiac causes:
  • Acute coronary syndrome
  • Cardiomyopathy
  • Congenital heart disease
  • Congestive heart failure (CHF)
  • Mitral valve prolapse
  • Pacemaker complication
  • Pericarditis
  • Myocarditis
  • Valvular disease
• Psychiatric causes:
  • Panic attack
  • Anxiety
  • Somatic Symptom Disorder
• Drugs and Medications:
  • Alcohol
  • Caffeine
  • Drugs of abuse (e.g. cocaine)
  • Medications (e.g. digoxin, theophylline)
  • Tobacco
• Misc
  • Anemia
  • Hyperthyroidism
    • Thyroid storm
  • Pulmonary embolism
  • Dehydration
  • Sepsis
  • Pheochromocytoma

Diagnosis

PSVT at ~180 bpm

Symptoms	Sinus tachycardia	SVT
History	volume loss	sudden onset
Physical Exam	dehydated	CHF-like
^Heart Rate	<180	>180
Variability	Yes	No

^In infants HR cuttoff = 220

Treatment

Termination of PSVT following adenosine

Unstable

• Synchronized cardioversion 0.5-1.0 J/kg
• Pediatrics: cardioversion at 0.5-1 J/kg. If unsuccessful, increase to 2 J/kg
• Consider giving sedation prior to cardioversion (unless in emergent situation)

Stable

• Vagal maneuvers
  • Pediatrics: often successful with ice application to face
  • Carotid sinus massage (ideal duration of 15 seconds)
    • Auscultate to r/o bruits in carotid artery before performing
    • Perform ONE side at a time
  • Valsalva maneuver (ideal duration of 10 seconds)
• Adenosine
  • 6mg IVP; 12mg IVP (if initial dose failed)
  • Contraindicated in asthmatics
• Calcium-channel blockers
  • Diltiazem 15–20mg IV over 2min
    • May give 25mg IV if inadequate response after 15min
    • If IV bolus worked start IV infusion at 5–20mg/hr
    • Contraindications: Hypotension, CHF, any suspicion of VT
  • Beta-blockers
    • Metoprolol 5mg IV q5min x 3; give 50mg PO if IVP effective
    • Esmolol 500mcg/kg IV over 60sec
      • May give repeat bolus if inadequate response after 2-5min
      • If effective start infusion at 50mcg/kg/min (titrate up to 300mcg/kg/min)
    • Contraindicated in asthmatics

See Also

• V Tach vs. SVT
• Tachycardia (Narrow)
• ACLS: Tachycardia
• PALS: Tachycardia