Mean Electrical Axis Flashcards
1
Q
What is a lead? (ECG)
A
The stretch between two limbs (arm or leg) electrodes
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
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
4
Q
What is the normal mean electrical axis of the ventricles?
A
0 and 90 degrees
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
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
7
Q
What is a myocardial infarction?
A
-deviations of the electrical axis occur to varying diseases