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EKG
EKG
25
Pharmacology
Graduate
01/25/2012

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Cards

Term
What does the EKG measure?
Definition
A composite of all APs generated across the surface of the heart.
Term
What does each grid box measure on the EKG?
Definition
0.04 seconds
Term
What is the maximum potential difference?
Definition
When half of a tissue is depolarized
Term
What is the baseline of the EKG
Definition
Before the p wave, when there is no potential difference between tissues.
Term
What is the p wave?
Definition
Movement of charge across the atria. Expected to take 0.09 seconds. Deflects positive.
Term
What is the PR interval?
Definition
The time it takes an impulse to start depolarizing the ventricles. Measured from P to Q, some people don't have Q. AV node is the major stopping point.
Term
When do the atria repolarize?
Definition
Under the QRS complex, not seen. Negative deflection.
Term
What is the QRS complex?
Definition
Ventricular depolarization. Q - movement across the septum. R - 50% of ventricle has been depolarized. S- Last part of ventricle, the left ventricular wall, depolarizes. All are a reflection of phase 0.
Term
What does it mean when the QRS complex is widened?
Definition
The impulse is slower reflecting a slowing in conduction.
Term
What is the ST segment
Definition
Measured from the S wave to the T wave, the amount of time it takes the ventricles to start depolarizing. Representative of phase 2. Prolong AP = Prolong ST = Prolong QT
Term
What is the T wave?
Definition
Repolarization of the ventricles, representative of phase 3.
Term
What is the QT interval?
Definition
Measured from the Q wave to the end of the T wave. Depolarization and repolarization of the ventricles, takes ~0.44 sec.
Term
What is the u wave?
Definition
Rarely seen, Repolarization of the papillary muscle.
Term
What are ways to see ischemia on the EKG?
Definition
Depression of the ST segment, elevation of the S wave.
Term
What is QTc?
Definition
Corrected for heart rate. A faster heart rate = shorter QT.
Term
How does charge move across the heart?
Definition
Negative to positive.
Term
What are the limb leads?
Definition
- Lead I - right arm to left arm
- Lead II - Right arm to left foot
- Lead III - Left arm to Left foot
Term
What is Einthoven's Law?
Definition
Voltage of Lead I + Voltage of Lead III = Voltage of Lead II. Avg direction of charge is toward Lead II. Can calculate a vector by having 2 leads.
Term
What are the augmented limb leads?
Definition
Unipolar. One positive electrode, other attachments negative
aVR - positive lead on right hand
aVL - positive lead on left hand
aVF - positive lead on left foot
Term
How does current flow?
Definition
From a depolarized area to a polarized area. Charge also moves from negative to positive.
Term
If current moves toward a positive electrode, how does it deflect?
Definition
Positive/up
Term
If current moves toward a negative electrode, how does it deflect?
Definition
Negative/down
Term
If myocardial tissue increases in mass in the direction of deflection how does that impact deflection?
Definition
The height of deflection increases.
Term
What does the T wave vector of the atria look like?
Definition
Inverted from the T wave of the ventricle, Up and to the left,
Term
How do the V leads work?
Definition
Positioned around the surface of the heart, one is always positive starting with V1. If current moves away from + electrode, deflection is negative. So as + moves along the V leads, deflection gets more and more positive.
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