Term
3 standard leads (I, II, III)
3 augmented leads (aVR, aVL, aVF)
6 precordial leads (V1-V6) |
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Definition
| list the leads of an ECG (12) |
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Term
| arrhtmias, ischemia, damage |
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Definition
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Term
| depolarization, repolarization (currents generated in the heart generate slight potential differences across the body surfaces ~1mV) |
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Definition
| what does an ECG measure? |
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Term
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Definition
| what do ECG measurements depend on? |
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Term
P: atrial depolarization
QRS: ventricular depolarization
T: ventricular repolarization |
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Definition
| define the following: P wave, QRS complex, T wave |
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Term
| the QRS supposedly hides it, even with an AV block |
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Definition
| why can't you see atrial repolarization on an ECG? |
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Term
| the peak of one ventricular deoplarization to the next, this is used to determine heart rate |
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Definition
| what is the RR inverval defined as? |
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Term
| the time between atrial contraction and the beginning of ventricular contraction normally is o.12-0.20 s |
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Definition
| what is the PR interval? what is its normal value? |
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Term
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Definition
| how long does it take before every part of the heart is depolarized? |
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Term
the time of ventricular contraction (how long it takes to de & repolarize)
normally = 0.35 s |
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Definition
| what is the QT inertval? what is its normal value? |
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Term
look at the R-R interval. Count the big boxes between the two peaks and divide 300 by this number.
This works because 5 * 60 = 300, and every 5 big boxes = 1 second so divide 300 by the # of boxes and you can estimate HR like it's nobody's business. |
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Definition
| how can you tell a person heart rate from the ECG? |
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Term
it means that the conduction is going through the muscle rather than the purkinje fibers
this is shown be a widened QRS complex |
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Definition
| what is an ectopic foci? how is this seen on an ECG? |
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Term
| ischemia & cardiac myocyte damage (chronically depolarized cells) |
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Definition
| what does an ST change indicate? |
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Term
180(-) right arm
0(+) left arm
points to positive |
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Definition
| what is the angle of the standard bipolar limb lead I? (indicate pos and negative) |
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Term
-120 (-) right arm
60 (+) left leg |
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Definition
| what is the angle of the standard bipolar limb lead II? (indicate pos and negative) |
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Term
| -60 (-) left arm 120 (+) left leg |
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Definition
| what is the angle of the standard bipolar limb lead III? (indicate pos and negative) |
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Term
| toward the positive electrode |
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Definition
| which direction does the vector point for the ECG leads? |
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Term
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Definition
| where do the vectors point for the augemented leads? (list the augmented leads and their angles (+)) |
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Term
| lead 2, the heart depolarizes at approximately the same angle |
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Definition
| on which lead will you see the strongest(best) QRS complex? why? |
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Term
they measure the augemented vector resulting from the potential that points toward either the right arm, left arm, or feet (the positive terminal points to the limb described in the name of the lead)
there are 2 negative electrodes on 2 limbs and a positive on one. This is like an average of the standard limb leads, and looks like them except aVR is inverted |
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Definition
| what do the augmented lead measure? |
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Term
| the electrical potential of any limb equals the sum of potentials of other two limb leads |
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Definition
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Term
| it is a triangle drawn around the heart that indicates fluids in the body have equal resistance, so the potential is carried equally |
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Definition
| what is Einthoven's triangle? |
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Term
| the negative potential of the body (sum of all potentials) located at the center of the heart |
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Definition
| whatdoes the negative end of the precordial(chest) leads represent? |
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Term
| anterior/posterior location (can tell you where a heart attack occurs) |
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Definition
| what do the chest leads(V1-V6) tell you? |
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Term
| 2 large boxes on the y axis |
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Definition
| on a typical ECG, what is 1 mV? |
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Term
| the voltage of the potential (mV) |
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Definition
| on an ECG, what is the length of the vector proportional to? |
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Term
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Definition
| if a vector is horizontal and points to the patients left, what angle is it at? |
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Term
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Definition
| a vector that points downwards is what angle? |
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Term
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Definition
| what does 5 large boxes on the x axis of an ECG represent? |
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Term
| instantaneous mean vector |
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Definition
| what is "A" in vector analysis ? |
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Term
| projected vector on the lead |
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Definition
| what is "B" in vector analysis? |
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Term
| the largest QRS, because the direction of polarization is most aligned with it |
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Definition
| the lead with the largest depolarization will be indicated by what? why? |
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Term
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Definition
| are the standard lead vectors negative or positive in the Q wave normally? |
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Term
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Definition
| are the standard lead vectors negative or positive in the R wave normally? |
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Term
I is positive, but II and III are negative
the action potential is headed toward the positive cathode of lead I (the left ventricle) so it is positive |
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Definition
| are the standard lead vectors negative or positive in the S wave normally? why? |
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Term
| the last to depolarize are the first to repolarize |
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Definition
| in a normal heart: the ____ area to depolarize is the ____ area to repolarize |
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Term
| changes in heart position, hypertophy, bundle branch blocks |
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Definition
| what 3 things can shift the axis of depolarization? |
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Term
| deep expiration, lying down, obesity (abdominal fat pushes up) |
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Definition
| what causes a change of position of the heart which results in a left shift? |
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Term
| deep inspiration, standing up, being Abe Lincoln(tall and thin with a long thorax) |
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Definition
| what causes a change of position of the heart which results in a right shift? |
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Term
| left shift (and right hypertrophy causes right shift) |
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Definition
| what kind of shift does left ventricular hypertrophy cause? |
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Term
| left shift (right BBB causes right shift) |
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Definition
| what kind of shift does a left bundle branch block cause? |
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Term
| the depolarization will be prolonged where the block is, so it is more positive (thats where the vector will shift to) |
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Definition
| why does a bundle branch block cause a shift in the direction of the block? |
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Term
use 2 leads, draw the vector at the proper angle for the lead, with a magnitude equal to the voltage (units) of the QRS
draw perpendicular lines from the ends of the vectors and then draw a line from the center (the original vector's intersection) to the place where th perpendicular lines meet.
this new line is the axis of depolarization |
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Definition
| how do you calculate the axis of depolarization? |
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Term
| the direction the heart is depolarizing, you can use this to determine if the angle is being shifted by something |
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Definition
| what does the axis of depolarization tell you? |
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Term
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Definition
| what is the current of injury most often caused by? |
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Term
| opposite of the injury, the injury is negatively charge and the vector always points towards the positive |
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Definition
| which direction does the current of injury vector point? why? |
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Term
| the place where the potential = 0, right after QRS (the whole ventricle is depolarized so there is no potential) |
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Definition
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Term
| standard and augmented leads |
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Definition
| which leads determine the left and right position of an injury? |
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Term
| the difference between the voltage of the ECG immediately before the onset of the P wave, and the J point (0 reference point) |
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Definition
| where is the injury potential in each lead? |
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Term
| 120 degrees aka right ventricle |
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Definition
| if the mean axis of injury is -30 degrees, where is the current of injury? |
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Term
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Definition
| what leads are used to determine anterior/posterior position of an injury? |
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Term
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Definition
| what does it mean if V2 is negative? |
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Term
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Definition
| what does it mean if V2 is positive? |
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Term
| mild ischemia (& shortening/lengthening of the QRS complex |
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Definition
| what can lead to an inverted t wave? |
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Term
| one of the branches of the bundle of his is blocked (left or right) so one of the ventricles depolarizes before the other |
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Definition
| what happens in a bundle branch block? |
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