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What is the significance of the QRS complex duration?
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It should be less than or equal to 0.12 seconds; longer durations may indicate abnormalities in ventricular depolarization.
Describe the orientation of electrodes in Lead II.
Negative electrode on the right arm, positive electrode on the left leg.
What determines the mean vector direction in an EKG?
The overall direction of positive electrical charge flow through the heart.
Which lead is most commonly used for rhythm strips and why?
Lead II, because it usually provides a clear view of the heart's electrical activity, from the right arm to the left leg, approximating the mean electrical axis of the heart.
Define the significance of the isoelectric line in an EKG.
An isoelectric line indicates no net movement of electrical activity or current perpendicular to the lead axis.
What is the normal duration for the PR interval on an EKG?
Less than or equal to 0.20 seconds.
What does the Q wave on an EKG indicate?
Septal depolarization.
How does ventricular depolarization appear on an EKG?
As the R wave, indicating depolarization towards the left ventricle.
In EKG terms, what does the T wave represent?
Repolarization of the ventricles.
Describe ventricular myocyte depolarization and its impact on EKG deflections.
Depolarization involves positive ions entering cells, causing upward deflection on the EKG when moving towards the positive electrode.
How does the direction of positive charge flow affect EKG deflections?
Flow of positive charges towards the positive electrode results in an upward deflection; flow away results in a downward deflection.
How can the size of EKG boxes help in measurement?
Large boxes (5 mm) represent 0.20 seconds and 1 mV; small boxes (1 mm) represent 0.04 seconds and 0.1 mV.
What does a prolonged QT interval indicate?
A risk of arrhythmias.
Explain what the PR segment signifies on an EKG.
The PR segment indicates the delay at the AV node.
What physiological process does the P wave on an EKG represent?
Atrial depolarization.
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