II. Definitions
- P Wave
- Electrical signal on EKG representing depolarization (and contraction) of the atria
- Start of the P Wave represents right atrial depolarization, and the end of the P Wave represents left atrial depolarization
III. Findings: Normal
- Upright and Monophasic: I, II, V3, V4, V5, V6
- Inverted: aVR
- Variable: III, avL, avF, V1, V2, V3
IV. Causes: P Wave Inversion in leads I, II, V3-V6 (narrow complex with normal ventricular rate)
- Ectopic atrial focus
- Junctional Rhythm (AV Nodal or proximal purkinje) with retrograde P Waves preceding the QRS
V. Causes: High Amplitude - Atrial hypertrophy or atrial dilatation
- Mitral valve or tricuspid valve disease
- Hypertension
- Cor Pulmonale
- Congenital Heart Disease
VI. Causes: Low Amplitude (short P Wave)
- Hyperkalemia (associated with a Tall T Wave)
VII. Causes: Wide P Wave (width >0.11 sec)
- Left atrial enlargement
VIII. Causes: Biphasic P Wave (second half negative in III or V1)
- Left Atrial Enlargement
IX. Causes: M shaped or notched P Wave
- M-Mitral or P-Mitrale: Left atrial enlargement
- Findings
- Over 0.04 seconds between peaks
- Taller in I than in III
X. Causes: Peaked P Wave
- P-Pulmonale: Right atrial enlargement
- Findings
- Tall and pointed P Wave >2.5 mm in the inferior leads
- P Wave is taller in Lead III than in I
XI. Causes: P Waves absent
- Precaution
- Look closely for regularly spaced "artifact" on the ekg (e.g. low voltage P Waves)
- Atrial Fibrillation or Atrial Flutter
- Sinoatrial Node block
- AV Nodal Rhythm
XII. References
- Berberian (2023) Crit Dec Emerg Med 37(5): 12-3