Flashcards in Introduction to the ecg Deck (24):
direction of action potentials from SA node
electrode placement and resultant signal
largest signal is PARALLEL vectors, no signal is perpendicular
three locations for electrodes- right arm, left arm, ll. recording is always at the POSITIVE end
Nodes and charge
LL always+, RA always -
what are the three main leads for EKG?
Lead I (RA to LA), Lead II (RA to LL), and Lead III (LA-LL)
what are the sections in an EKG waveform
P, QRS, T, U
atrial depolarization after SA firing
ventricular depolarization and atrial repolarization
QRS waveform is composed of
four mean vectors, each with length related to size of muscle. LBB fires faster than the right.
augmented chest leads
AVL: -30, AVR: -150, AVF (+90)
additional positive electrodes referenced against the others.
determine net amplitude of QRS- count number of boxes, transfer values to axes, draw perpendicular lines, draw resultant vector
find lead without signal- mean vector is at a right angle!
what is a lead
a lead is a pair of electrodes. Only worry about two at a time. provideys electrical axis.
x axis and y axis of waveform
x axis: time, y axis: amplitude
amount of time to pass through juncitional fibers of AV
depolarized ventricles, plateau phase of ventricular AP
QRS segment vector 1
the q wave: points to the right, because conduction is LR (Left depolarizes faster). negative signal, towards neg electrode
QRS segment vector 2
R wave, depolarization of axis . down lead II, large mass of tissue
QRS segment vector 3
R wave, ventricular wall depolarization outward, to left cause of larger mass
QRS segment vector 4
S wave, end of V depolarization, upwards because base of heart depolarizes last. (neg, towards neg)
negative signal, depolarization away from positive,
small Q/R, almost right angle to depolarization