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Cardiology Chapter 1
Terms in this set (50)
EKG waves reflect the electrical activity of which cells?
Myocardial Cells, which make up the bulk of the heart.
Horizontal one small square represents
Horizontal one large square represents
Vertical one small square represents
Vertical one large square represents
Parts of the P Wave
Because the sinus node is located in the right atrium, it depolarizes before the left. So the first part of the P wave represents the right atrial depolarization, and the second part represents left atrial depolarizations
AV Nodes purpose
Slows conduction from the atria to the ventricles which allows the atria to finish contracting before the ventricles begin to contract. Allowing the atria to empty their blood volume completely.
Bundle of His Physiology
Directly after the AV node, almost immediately divides into right and left bundle branches
Right Bundle Branch physiology
carries current down the right side of the inter-ventricular septum to the apex of the right ventricle
Left Bundle Branch Physiology
Separates into three fasicles. Septal Fasicle (depolarizing interventricular septum)..... Anterior Fascicle( anterior wall of left ventricle) ... Posterior Fasicle (posterior wall of left ventricle).
small branches from the bundle branches that deliver electrical current to the ventricular myocardium
Why is QRS bigger than P Wave
QRS shows ventricular contraction which has much more mass than the atria.
first deflection downward
First upward deflection
Second upward deflection, if it is there
First downward deflection following an upward deflection.
Ventricular Repolarization (much slower process, so it's a longer wave).
A straight line connecting 2 waves
Encompasses one wave plus the connecting straight line.
PR Interval measures
start of atrial depolarization to start of ventricular depolarization.
Depolarization moving toward an electrode shows as a
Lead 1 created by making
left arm positive, right arm negative
Lead II created by making
legs positive, and right arm negative
Lead III created by making
legs positive, left arm negative.
Augmented leads are chosen by
a single lead being positive and all the others negatives
aVL created by
left arm positive, all other limbs negative
aVR created by
right arm positive, all others negative
aVF created by
legs positive and others negative
The six leads of the frontal plane
What are the six leads and their angles?
The six precordial leads are made by
making each chest electrode positive in turn, and the rest of the body a common ground.
V1 placed where
fourth intercostal space, right of sternum
V2 placed where
fourth intercostal space, left of sternum
V3 placed where
Between V2 and V4
V4 placed where
fifth intercostal space, midclavicular line
V6 placed where
fifth intercostal space midaxillary line
V1 lies directly over
V2 and V3 lie directly over
V4 lies over
apex of left ventricle
V5 and V6 lie
over the lateral left ventricle
What leads are considered anterior, left lateral, inferior, right ventricular?
Any lead that views atrial depolarization moving toward will will record as
a positive deflection
What do P waves look like in AVR, Lead I, and Lead III?
What do P waves look like in V1 and V6?
How will lead III P wave change if the heart is rotated counter clockwise 45 degrees?
Septal Depolarization physiology
Shows as Q wave, from the septal fascicle of the left bundle branch. Not always visible on EKG. It is left to right depolarization. Seen in leads I, AVL, V5, V6. .. sometimes in V3 and V4.
What happens in leads aVR, I, and II in QRS? Which one has a Q wave and why?
Lead I has Q wave because it is septal depolarization from left to right, depolarization is going away from the lead so it is a negative deflection.
S Wave in V1 V5 and V6
S wave in V1 is deep S wave because current is moving leftward, away from it. V5 and V6 have large positive R waves because current is moving toward it.
V3 and V4 in the QRS
one of these is usually biphasic, with R and S wave in nearly equal amplitude
When is T wave positive?
Repolarization begins in the lsat area to be depolarized, and then travels backward, in teh direction opposite of depolarization. Because both an approaching wave of depolarization and a receding wave of repolarization generate a positive deflection on the EKG. The same electrodes that recorded a positive deflection during depolarization (tall R wave) generally also show positive deflection during repolarization (positive T wave).
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