Cardiovascular Medicine Book




Left Axis Deviation

Aka: Left Axis Deviation, Left QRS Axis
  1. See Also
    1. QRS Axis
    2. Right Axis Deviation
    3. Electrocardiogram
    4. Cardiac Electrophysiology Anatomy
  2. Definition
    1. Deviation into lead aVL axis (-30 to-90 degrees)
    2. Negative net QRS voltage in lead avF (and lead II)
    3. Positive net QRS voltage in lead I
    4. On a clock face, 2:00 to 12:00 position
  3. Interpretation: Based on most isoelectric lead
    1. Images
      1. EKG-Axes.png
    2. Approach
      1. See QRS Axis
      2. Lead with most symmetric voltage (as much positive QRS voltage as negative QRS voltage)
      3. Choose lead that is perpendicular to isoelectric lead and that leads axis is the same as the QRS Axis
    3. Left Axis Deviation (-90 to -30, positive in lead I and negative in lead avF)
      1. Most Isoelectric I (avF is perpendicular): -90 (12:00)
      2. Most Isoelectric avR (III is perpendicular): -60 (1:00)
      3. Most Isoelectric II (avL is perpendicular): -30 (2:00)
  4. Interpretation: Pathologic Left Axis Deviation
    1. Left Posterior Hemiblock (rare due to dual supply)
    2. Left Anterior Hemiblock
      1. QRS Axis more negative than -30 degrees (AVL)
      2. Axis <-30 if Lead II is more negative than positive
  5. Causes
    1. Normal variant
    2. Mechanical shift
      1. Ascites
      2. High diaphragm
    3. Left Atrial hypertrophy
    4. Left Bundle Branch Block
    5. Wolf-Parkinson-White Syndrome (WPW Syndrome)
    6. Chronic Obstructive Pulmonary Disease (COPD)
    7. Hyperkalemia
    8. Right ventricular ectopic rhythms
  6. Causes: Non-Causes of Left Axis Deviation
    1. Left Ventricular Hypertrophy is not a deviation cause

Left axis deviation (C0232297)

Concepts Finding (T033)
SnomedCT 39732003, 164952002, 142124001
English Ekg Left Axis Deviation, Left axis deviation by EKG, left axis deviation, left axis deviation ekg, axis deviation left, axis deviation ekg left, Left axis deviation, LAD - Left axis deviation, Left axis deviation (finding)
Spanish signos electrocardiográficos de desviación del eje hacia la izquierda (hallazgo), signos electrocardiográficos de desviación del eje hacia la izquierda
Derived from the NIH UMLS (Unified Medical Language System)

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