Lesson 4: Vector

Lesson 4: Mean Electrical Vector

• Represents average current flow of action potentials at a specific time.

• EKG waveform measures the mean electrical vector.

EKG Deflections

• Positive deflection: Vector of depolarization towards positive electrode.

• Negative deflection: Vector of depolarization away from positive electrode.

• Biphasic deflection: Vector travels perpendicular to positive electrode.

EKG Leads

• Categories:

  • Bipolar leads: I, II, III

  • Limb leads: aVR, aVL, aVF

  • Precordial leads: V1-V6

• Mapping leads to coronary arteries for diagnosing myocardial ischemia:

  • Right coronary artery: Inferior heart (II, III, aVF)

  • Circumflex artery: Left lateral heart (I, aVL, V5, V6)

  • Left coronary artery: Anterior heart (V1-V4)

Vectors in Action Potentials

• Two key vectors:

  1. Vector of depolarization

  2. Vector of repolarization

• Each myocyte generates an action potential moving in various directions.

Deflections and Current Direction

• Positive deflection -> vector towards positive electrode.

• Negative deflection -> vector away from positive electrode.

• Biphasic deflection -> vector perpendicular to positive electrode.

Depolarization and Repolarization

• Depolarization (QRS Complex):

  • Direction: Base to apex, endocardium to epicardium.

  • Polarity: From internally (-) to internally (+).

  • Produces a positive current.

• Repolarization (T Wave):

  • Direction: Apex to base, epicardium to endocardium.

  • Polarity: From internally (+) to internally (-).

  • Produces a negative current.

• Repolarization vector often points in the same direction as depolarization due to opposite direction and negative current relationship.