# Shared Flashcard Set

## Details

ECG (arrythmias in separate set of cards))
Wacker 3/14/11 lecture -2 hrs
55
Physiology
03/07/2011

## Additional Physiology Flashcards

Term
 3 standard leads (I, II, III)3 augmented leads (aVR, aVL, aVF)6 precordial leads (V1-V6)
Definition
 list the leads of an ECG (12)
Term
 arrhtmias, ischemia, damage
Definition
 what does an ECG detect?
Term
 depolarization, repolarization (currents generated in the heart generate slight potential differences across the body surfaces ~1mV)
Definition
 what does an ECG measure?
Term
 mass of myocardium
Definition
 what do ECG measurements depend on?
Term
 P: atrial depolarizationQRS: ventricular depolarizationT: ventricular repolarization
Definition
 define the following: P wave, QRS complex, T wave
Term
 the QRS supposedly hides it, even with an AV block
Definition
 why can't you see atrial repolarization on an ECG?
Term
 the peak of one ventricular deoplarization to the next, this is used to determine heart rate
Definition
 what is the RR inverval defined as?
Term
 the time between atrial contraction and the beginning of ventricular contraction normally is o.12-0.20 s
Definition
 what is the PR interval? what is its normal value?
Term
 0.22 s
Definition
 how long does it take before every part of the heart is depolarized?
Term
 the time of ventricular contraction (how long it takes to de & repolarize)normally = 0.35 s
Definition
 what is the QT inertval? what is its normal value?
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.
Definition
 how can you tell a person heart rate from the ECG?
Term
 it means that the conduction is going through the muscle rather than the purkinje fibersthis is shown be a widened QRS complex
Definition
 what is an ectopic foci? how is this seen on an ECG?
Term
 ischemia & cardiac myocyte damage (chronically depolarized cells)
Definition
 what does an ST change indicate?
Term
 180(-) right arm0(+) left arm points to positive
Definition
 what is the angle of the standard bipolar limb lead I? (indicate pos and negative)
Term
 -120 (-) right arm 60 (+) left leg
Definition
 what is the angle of the standard bipolar limb lead II? (indicate pos and negative)
Term
 -60 (-) left arm 120 (+) left leg
Definition
 what is the angle of the standard bipolar limb lead III? (indicate pos and negative)
Term
 toward the positive electrode
Definition
 which direction does the vector point for the ECG leads?
Term
 aVR: -150aVL: -30aVF: 90
Definition
 where do the vectors point for the augemented leads? (list the augmented leads and their angles (+))
Term
 lead 2, the heart depolarizes at approximately the same angle
Definition
 on which lead will you see the strongest(best) QRS complex? why?
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
Definition
 what do the augmented lead measure?
Term
 the electrical potential of any limb equals the sum of potentials of other two limb leads
Definition
 what is Einthoven's law?
Term
 it is a triangle drawn around the heart that indicates fluids in the body have equal resistance, so the potential is carried equally
Definition
 what is Einthoven's triangle?
Term
 the negative potential of the body (sum of all potentials) located at the center of the heart
Definition
 whatdoes the negative end of the precordial(chest) leads represent?
Term
 anterior/posterior location (can tell you where a heart attack occurs)
Definition
 what do the chest leads(V1-V6) tell you?
Term
 2 large boxes on the y axis
Definition
 on a typical ECG, what is 1 mV?
Term
 the voltage of the potential (mV)
Definition
 on an ECG, what is the length of the vector proportional to?
Term
 0 degrees (like lead I)
Definition
 if a vector is horizontal and points to the patients left, what angle is it at?
Term
 positive 90 degrees
Definition
 a vector that points downwards is what angle?
Term
 1 second
Definition
 what does 5 large boxes on the x axis of an ECG represent?
Term
 instantaneous mean vector
Definition
 what is "A" in vector analysis ?
Term
 projected vector on the lead
Definition
 what is "B" in vector analysis?
Term
 the largest QRS, because the direction of polarization is most aligned with it
Definition
 the lead with the largest depolarization will be indicated by what? why?
Term
 all positive
Definition
 are the standard lead vectors negative or positive in the Q wave normally?
Term
 all positive
Definition
 are the standard lead vectors negative or positive in the R wave normally?
Term
 I is positive, but II and III are negativethe action potential is headed toward the positive cathode of lead I (the left ventricle) so it is positive
Definition
 are the standard lead vectors negative or positive in the S wave normally? why?
Term
 the last to depolarize are the first to repolarize
Definition
 in a normal heart: the ____ area to depolarize is the ____ area to repolarize
Term
 changes in heart position, hypertophy, bundle branch blocks
Definition
 what 3 things can shift the axis of depolarization?
Term
 deep expiration, lying down, obesity (abdominal fat pushes up)
Definition
 what causes a change of position of the heart which results in a left shift?
Term
 deep inspiration, standing up, being Abe Lincoln(tall and thin with a long thorax)
Definition
 what causes a change of position of the heart which results in a right shift?
Term
 left shift (and right hypertrophy causes right shift)
Definition
 what kind of shift does left ventricular hypertrophy cause?
Term
 left shift (right BBB causes right shift)
Definition
 what kind of shift does a left bundle branch block cause?
Term
 the depolarization will be prolonged where the block is, so it is more positive (thats where the vector will shift to)
Definition
 why does a bundle branch block cause a shift in the direction of the block?
Term
 use 2 leads, draw the vector at the proper angle for the lead, with a magnitude equal to the voltage (units) of the QRSdraw 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
Definition
 how do you calculate the axis of depolarization?
Term
 the direction the heart is depolarizing, you can use this to determine if the angle is being shifted by something
Definition
 what does the axis of depolarization tell you?
Term
 ischemia
Definition
 what is the current of injury most often caused by?
Term
 opposite of the injury, the injury is negatively charge and the vector always points towards the positive
Definition
 which direction does the current of injury vector point? why?
Term
 the place where the potential = 0, right after QRS (the whole ventricle is depolarized so there is no potential)
Definition
 what is the "J point"
Term
 standard and augmented leads
Definition
 which leads determine the left and right position of an injury?
Term
 the difference between the voltage of the ECG immediately before the onset of the P wave, and the J point (0 reference point)
Definition
 where is the injury potential in each lead?
Term
 120 degrees aka right ventricle
Definition
 if the mean axis of injury is -30 degrees, where is the current of injury?
Term
Definition
 what leads are used to determine anterior/posterior position of an injury?
Term
 anterior infacrt
Definition
 what does it mean if V2 is negative?
Term
 posterior infarct
Definition
 what does it mean if V2 is positive?
Term
 mild ischemia (& shortening/lengthening of the QRS complex
Definition
 what can lead to an inverted t wave?
Term
 one of the branches of the bundle of his is blocked (left or right) so one of the ventricles depolarizes before the other
Definition
 what happens in a bundle branch block?
Supporting users have an ad free experience!