P Wave


P Wave, P Pulmonale, P Mitrale

  • 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
  • Findings
  • Normal
  1. Upright and Monophasic: I, II, V3, V4, V5, V6
  2. Inverted: aVR
  3. Variable: III, avL, avF, V1, V2, V3
  • 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
  • Causes
  • High Amplitude - Atrial hypertrophy or atrial dilatation
  1. Mitral valve or tricuspid valve disease
  2. Hypertension
  3. Cor Pulmonale
  4. Congenital Heart Disease
  • Causes
  • Low Amplitude (short P Wave)
  1. Hyperkalemia (associated with a Tall T Wave)
  • Causes
  • Wide P Wave (width >0.11 sec)
  1. Left atrial enlargement
  • Causes
  • Biphasic P Wave (second half negative in III or V1)
  1. Left Atrial Enlargement
  • 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
  • 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
  • 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
  • References
  1. Berberian (2023) Crit Dec Emerg Med 37(5): 12-3