II. Definition

  1. Form of Supraventricular Tachycardia (60% of cases) in which reentry occurs within the AV Node
  2. AV Node in AVNRT contains two pathways (one slow and one fast)

III. Epidemiology

  1. Most common in young women
  2. Typically there is no underlying structural heart disease
  3. Increased onset with low Estrogen and high Progesterone states
    1. Luteal Phase of Menstrual Cycle (after Ovulation)
    2. Less common during pregnancy

IV. Findings: General

  1. Heart Rate typically 160 to 190 (up to 260)
  2. P Waves are often hidden within the QRS (or appear immediately after the QRS)

V. Types: Typical (slow/fast) - 90% of AVNRT

  1. Course
    1. Starts with PAC passed down slow accesory path
    2. Signal travels retrograde up fast path
    3. Signal cycles back down slow accesory pathway
  2. EKG findings
    1. PR interval > RP Interval
    2. Negative P Waves in III and avF

VI. Types: Atypical (fast/slow) - 10% of AVNRT

  1. Course: Reverse of typical pathway
  2. EKG findings
    1. PR interval < RP Interval
    2. Pseudo-S Wave in leads I, II, aVF

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