Mean Electrical Axis Flashcards

1
Q

What is a lead? (ECG)

A

The stretch between two limbs (arm or leg) electrodes

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2
Q

What is Einthovens triangle?

A

-used to determine the electrical axis of the heart

  • Einthoven named the leads between the 3 limb leads electrodes “standard lead I, II, III” referring to the two arm electrodes and the left leg electrode
    • he studied the relationship between theses electrodes forming a triangle where the heart electrically constitutes the null point
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3
Q

What is the mean axis of depolarization?

A
  • the average direction of depolarization during the cardiac cycle
    • can be done by observing the voltages of the ARS complex from two different perspectives using two different leads
    • Lead I: horizontal axis from left arm to right arm
    • Lead II: Axis from Right arm to left leg
    • Lead III:axis from left arm to left leg
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4
Q

What is the normal mean electrical axis of the ventricles?

A

0 and 90 degrees

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5
Q

What is ventricular hypertrophy?

A
  • enlargement of one ventricle shifts the mean axis of depolarization toward the hyperthyroid ventricle because it takes longer to depolarize the larger ventricle
    • a left axis deviation occurs when the left ventricle is hypertrophied
    • a right axis deviation occurs when the right ventricle hypertrophies
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6
Q

What is a bundle branch block?

A
  • a conduction block in one of bundle of His, depolarization will be much slower in the blocked ventricle.
    • In the left bundle -branch block, depolarization will occur more slowly in the left ventricle than the right ventricle, and the mean electrical axis will deviate to the left
    • in the right bundle branch block, there will be a right axis deviation
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7
Q

What is a myocardial infarction?

A

-deviations of the electrical axis occur to varying diseases

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