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60 Cards in this Set
- Front
- Back
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If the direction of the lead is in parallele with the direction of the dipole, what type of deflection will be seen?
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A positive deflection
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What are 3 factors that affect the amplitude of electrical vectors?
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1. Mass of muscle generating signal (hypertrophy = big vectors)
2. Conduction Velocity (fast = big) 3. Degree of cancellation of electrical forces |
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What are the 6 frontal plane leads and what is their orientaiton?
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I: 0
II: 60 III: 120 aVL: -30 aVR: -150 aVF: 90 |
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What is the central terminal of wilson?
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The "virtual" negative pole created in the back of the chest for the chest leads, created by combining the limb leads to create negative lead
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What are the orientation of the 6 chest leads?
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V1: out/slight right from chest
V2: slight left V3/4/5: Progressively more left V6: 90 to the left |
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What are the 3 main waveforms seen in a normal EKG?
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1. P wave
2. QRS complex 3. T wave |
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The P wave represents what?
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Atrial depolarization
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The QRS complex represents what?
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Ventricular Depolarization
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The ST segment represents what?
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Ventricular plateua
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The T wave represents what?
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Ventricular repolarization
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Why is the SA node depolarization and AV node depolarization not seen on an EKG?
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Too small volume of tissue
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Why is atrial repolarization not seen?
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Too slow of a process
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What is a Q wave?
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The first downward deflection of the QRS compelx
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What is the R wave?
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The first upward deflection of the QRS complex
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What is the S wave?
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The downward deflection after the R wave in the QRS complex
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What is R'?
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A second upright deflection in a QRS compelx
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What is the 5 step process to analyzing an EKG?
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1. Rate
2. Rhythm 3. Intervals (PR/QRS/QT) 4. QRS axis 5. Configuration (P wave/QRS/ST segment, T wave) |
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Each large box in the EKG is how many seconds?
Small box? |
Big: .2 (200ms)
Small: .04 (40ms) |
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How is HR calculated?
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300 / # of big boxes
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What items are looked at to determine rhythm?
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1. Upright P waves in I, II, III, (and aVF)
2. Rate between 60-100 3. P wave precedes each QRS (when HR is <120) 4. Are QRS normal or wide? 5. Is ventricular rhythm regular? 6. Do p waves come from sinus node? |
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The initial portion of the QRS wave represents what?
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Depolarization of intraventricular septum
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The mid/late portions of QRS complex represent what?
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Right and left ventricular depolarization
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Describe the direction of depolarization in the ventricles?
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Depolarization spreads from left bundle, through the septum from the LV to RV
The creates vectors pointing to the right and anterior |
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The orientation of ventricular depolarization gives what reading on V1 and V6?
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V1: R wave
V6: Q wave |
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In the middle/late parts of ventricular depol, where is the net vector pointing?
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Toward the left ventricular apex
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Normal rhythm is called what?
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Normal Sinus Rhythm
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Sinus rhythm with HR >100 is what?
<60? |
>100: Sinus tachycardia
<60: Sinus bradycardia |
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What is the first step in determining the nature of an abnormal rhythm?
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Determine whether it is supraventriucular or ventriuclar in nature
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What does a supraventriuclar rhythm look like?
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Have P wave before every QRS
QRS duration is normal (unless there is a conduction block in one of the bundle branches) |
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What does ventricular rhythm look like?
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Always associated with wide QRS (because activation of the rest of the ventricles doesn't utilized the rapid conduction His Purkinje system)
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What are the 3 intervals that are measured?
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PR, QRS, QT
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What is the PR interval?
What does it represent? What is normal? |
From beginning of P wave to beginning of QRS complex
Represents delay between atrial and ventricular depolarization Normal: 0.12 - 0.20 sec |
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What is QRS?
What does it represent? What is normal? |
Beginning to end of QRS
Represents time to depolarize entire ventricle Normal: <0.10 sec |
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A long QRS indicates what?
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Indicates either that there is either a conduction block in one of the bundle branches or that the beat is arising in ventricular muscle
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What is QT?
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ME haha
Beginning of QRS complex to end of T wave |
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In a bundle branch block, will there be a P wave before the QRS?
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YES
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Will there be a P wave in front of the QRS in ventricular beats?
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NO
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What is the biggest factor to cause a change in the QT interval?
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Change in the ventricular AP duration
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What is normal for QT?
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Should be about 0.40 seconds when HR is 60
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What is the QRS axis?
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The mean vector orientation of the QRS axis in the frontal plane
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QRS axis is calculated using which leads?
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Frontal leads
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What is normal QRS?
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-30 to +90
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What is configuration?
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The shape, morphology of the different waves (to be discussed in more detail in further lectures)
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What is the first part of the ventricle to be activated during the beginning of the QRS?
What is the orientation vector |
Intraventricular septum
vector: LV to RV which is anteriorly and to the R |
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How does septal depolariation appear in the V leads?
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As small R wave in V1 and small Q wave in V6
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During the middle of the QRS, where is the orientaion vector?
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Points leftward, toward the ventricular apex
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How should the QRS look on the V leads?
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Should have characteristic progression of R wave size from V1 to V6
Should be negative in V1, positive in V6, I and II |
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In which direction should a normal T wave point?
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Same direction as QRS
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If the T wave represents repolarization, why is it in the same direcition as QRS?
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Because it has opposite orientation.
Depolarization: Endocardium to epicardium Repolarization: Epicardium to endocardium bc epicardial AP's are shorter |
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What is AV block?
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Delay or conduction failure in the conduction pathway between the atria and ventricles
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What is first degree AV block?
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One to one AV conduction with conduction delay
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What is seen on the EKG is first degree AV block?
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every p wave is followed by a QRS, but PR interval is greater than 0.20 seconds (one large box)
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What is second degree AV block?
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Intermittent conduction block between atria and ventricles
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What is seen on the EKG is second degree AV block?
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some P waves are followed by QRS complexes and some are not
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What is third degree AV block?
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Complete conduction block between Atria and Ventricles
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What is seen on the EKG on third degree block?
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P wave and QRS are regular, but are independent of each other. Sometimes might see P wave before, sometimes after
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What is bundle branch block?
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Block in his-purkinje bundles going to the ventricles
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What are the best leads for diagnosing bundle branch block?
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I, V1, and V6
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What is seen on the EKG in R bundle branch block?
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Left ventricular activation is normal, so first part of QRS is normal (R wave in I and V6)
Broad S wave in QRS in I and V6, and a broad R' in V1 - because RV is activated late Overall: "M" shaped pattern in V1: RSR' |
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What is seen on the EKG in L bundle branch block?
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Wide R wave in leads I, V6
Wide S wave in V1 Because RV is activated normally, but LV is activated late by slow conduction through ventricular muscle from RV |
