II. Definitions

  1. P Wave
    1. Electrical signal on EKG representing depolarization (and contraction) of the atria
    2. Start of the P Wave represents right atrial depolarization, and the end of the P Wave represents left atrial depolarization

III. Findings: Normal

  1. Upright and Monophasic: I, II, V3, V4, V5, V6
  2. Inverted: aVR
  3. Variable: III, avL, avF, V1, V2, V3

IV. Causes: P Wave Inversion in leads I, II, V3-V6 (narrow complex with normal ventricular rate)

  1. Ectopic atrial focus
  2. Junctional Rhythm (AV Nodal or proximal purkinje) with retrograde P Waves preceding the QRS

V. Causes: High Amplitude - Atrial hypertrophy or atrial dilatation

  1. Mitral valve or tricuspid valve disease
  2. Hypertension
  3. Cor Pulmonale
  4. Congenital Heart Disease

VI. Causes: Low Amplitude (short P Wave)

  1. Hyperkalemia (associated with a Tall T Wave)

VII. Causes: Wide P Wave (width >0.11 sec)

  1. Left atrial enlargement

VIII. Causes: Biphasic P Wave (second half negative in III or V1)

  1. Left Atrial Enlargement

IX. Causes: M shaped or notched P Wave

  1. M-Mitral or P-Mitrale: Left atrial enlargement
  2. Findings
    1. Over 0.04 seconds between peaks
    2. Taller in I than in III

X. Causes: Peaked P Wave

  1. P-Pulmonale: Right atrial enlargement
  2. Findings
    1. Tall and pointed P Wave >2.5 mm in the inferior leads
    2. P Wave is taller in Lead III than in I

XI. Causes: P Waves absent

  1. Precaution
    1. Look closely for regularly spaced "artifact" on the ekg (e.g. low voltage P Waves)
  2. Atrial Fibrillation or Atrial Flutter
  3. Sinoatrial Node block
  4. AV Nodal rhythm

XII. References

  1. Berberian (2023) Crit Dec Emerg Med 37(5): 12-3

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