Advanced ECG Flashcards
cardiac conduction pathway 10
1 sa node 2 anterior internodal fascicle 3 middle internodal fasicle (wenckebach bundle) 4 posterior internodal fascicle (thorels pathway) 5 bachman bundle 6 av node 7 bundle of his 8 RBB 9 LBB 10 Purkinje fibers
phase 4 non pacer action potential electrical conduction cells
resting membrane potential -90
phase 0 non pacer action potential electrical conduction cells
depolarization
na moves intracellular
phase 1 non pacer action potential electrical conduction cells
start repolarization
K moves extracellular
phase 2 non pacer action potential electrical conduction cells
plateau phase
Ca moves intracellular
phase 3 non pacer action potential electrical conduction cells
finishes repolarization
Ca channel close
SA node action potential phase 4
spontaneous repolarization
Na and Ca constantly in
SA node action potential phase 0
slow depolarization
Ca in
SA node action potential phase 3
repolarization ca channel open k open (out)
what action potential has the fastest repolarization?
SA node
limb leads
I, II, III, aVR, aVL, aVF
standard/bipolar limb leads
I, II, III
augmented/unipolar limb leads
aVR, aVL, aVF
in what orientation do the limb leads examine the heart through
frontal plane
bipolar limb leads
positive and negative electrodes
current moves from neg to pos
Lead I
180 to 0
right arm to left arm
Lead II
-120 to 60
right arm to left leg
Lead III
-60 to 120
left arm to left leg
augmented unipolar leads
obtained by modifying the bipolar limb leads
ONLY have positive electrode
naming unipolar limb leads “a” stand for
augmented or modified
naming unipolar limb leads “v” stands for
vector
vector can point to positive electrode on left or right or foot
naming unipolar limb leads “R,L,F” stands for’?
where the postive electrode is
example: aVR - postitive electrode is in right arm
Lead aVR created?
modified lead III
left arm and left leg cancel out to create positive electrode going towards right arm
aVR degrees
30 to -150
Lead aVL created?
modified lead II
right arm and left leg cancel out and create positive electrode going to left arm
aVL degrees
150 to -30
lead aVF created?
modification of lead I
right arm and left arm cancel out and create positive electrode going to foot
aVF degrees
-90 to 90
mean electrical axis
main cardiac vector
sum of all of the MANY vectors of electricity that the heart makes
what leads does the mean electrical axis apply to?
only limb leads
normal QRS axis (MEA)
-30 to 110
left axis deviation
cardiac vector falls within -30 to -90 range
possible causes of left axis deviation
LVH
inferior wall MI
right axis deviation
90 to 180
possible causes of right axis deviation
RVH
young age (children have larger RV)
dextrocardia
extreme right axis deviation
-90 to -180
if the MEA vector travels the same direction as the lead youre using how will that effect the R wave
positive R wave deflection
if the MEA vector travels the opposite direction as the lead youre using how will that effect the R wave
negative R wave deflection (inverted)
if the MEA vector travels perpendicular to the lead youre using how will that effect the R wave
equiphasic deflection of the r wave
if a pt has a normal QRS axis then the R wave will be ______ in lead aVR
negative (inverted)
if a pt has a normal QRS axis then the R wave will be ______ in lead II
positive (upright)
if a pt has a normal QRS axis then the R wave will USUALLY be ____ in lead I
upright
if a pt has a left axis deviation then the R wave will be _____ in lead I
positive (upright)
if a pt has a left axis deviation then the R wave will be ____ in leads II,III, aVF
negative (inverted)
if a pt has a right axis deviation then the R wave will be ____ in leads III, AVF
positive (upright)
if a pt has a right axis deviation then the R wave will be _____ in leads I aVL
negative (inverted)
precordial leads
V1-V6
what plane to the precordial leads examine the heart in?
horizontal (transverse)
Right precordial leads
v1, v2
2nd intercostal space
left precordial leads
v3-v6