lecture 1 (chapter 1, 2, 4 and 7) Flashcards
beat of the heart is due to a rhythm discharge of ____ stimuli
electrical
the information recorded on the EKG represents the hearts _____ activity
electrical
most of the information on the EKG represents electrical activity of _____ of the myocardium
contraction
while in the resting state, myocytes are polarized, the interior of every cell being ______-ly charged
negatively
the interiors of resting myocytes are negative, but when these cells are depolarized, their interiors become ____ and the cells contract
positive
myocardial contraction is caused by_______ of the mycoytes
depolarization
a wave of depolarization advancing through the myocardium is a moving wave of _____ charges
positive
what is the heart’s predominant pacemaker
SA node
the ability of the SA node to generate pacemaking stimuli is known as _____
automaticity
atrial depolarization is recorded as a ____ wave on EKG
P
depolarization of the ventricular myocytes produces a ____ complex on the EKG and initiates contraction of the ventricles
QRS
the QT interval represents the duration of ventricular ____ and is measured from the beginning of the QRS until the end of the T wave
systole
when is the QT interval considered normal
when it is less than half of the R-to-R interval at normal rates
the release of free Ca++ ions into the interiors of the myocytes produces myocardial
contraction
following depolarization, repolarization is due to the controlled outflow of ____ ions from the myocytes
K+
the amount of time represented by the distance between 2 heavy black lines is ____
0.2 of a second
each small division (measured horizontally between 2 fine lines) represents ____
0.04 of a second
what leads are considered lateral leads
leads I and IVL
what leads are considered inferior leads
II, III, and AVF
if leads V1 through V6 are imagined to be spokes of a wheel, the center of the wheel is the ____
AV node
lead V2 describes a straight line directly from the front to the back of the patient. In the lead V2 the patients back is considered ____
negative
when examine an EKG, you should determine the ____ first
rate
what do ventricular automaticity foci all pace within the range of
20-40 per minute range
what is the only conduction like between the aura and the ventricular conduction system below
AV node
define arrrhythmia
without rhythm
axis refers to the _____of depolarization as it passes through the heart
direction
there is increased depolarization in a ____ ventricle
hypertrophied
if the mean QRS vector points toward the right, we expect the QRS complex in lead I to be ____
negative
if the QRS in lead I is upright, the vector points to the patient’s
left
the chest leads form the _____ plane
horizontal
the chest electrode used for recording lead V2 is always _____
positive
a wave of depolarization traveling towards a positive EKG electrode causes a/an ____ deflection of the EKG tracing
upward/positive
a wave of depolarization traveling away from a positive EKG electrode causes a/an _____ deflection on the EKG tracing
negative/downward
describe the PR interval
distance (time) from beginning of P wave to beginning of QRS complex
describe the QT interval
distance (time) from beginning of QRS complex to end of T wave
describe the ST interval
distance (time) from end of QRS complex to end of T wave
what phase is the ST segment
plateau phase
what is the most widely accepted cause for the U wave
depolarization of the purkinje fibers
what does the vertical axis of the tracing represent
voltage
what does 1mm equal at standard calibration of the vertical axis
0.1 mV
what does the horizontal axis of the tracing represent
time
what does 1 mm at standard paper speed on the horizontal axis represent
0.04 sec/ 40 msec
how many big blocks are there per second
5
how many big blocks are there per minute
300
what plane are the precordial leads in
horizontal
describe the 3 bipolar limb leads
each has 1 positive and 1 negative electrode
describe the 3 augmented unipolar limb leads
each has 1 positive electrode and 1 compound reference electrode
describe lead 1 and AVF with normal EKG (rotation)
both are upward
describe lead 1 and AVF with R.A.D.
lead 1 is downward; AVF is upward
describe lead 1 and AVF with extreme R.A.D.
lead 1 and AVF are both downward
describe lead 1 and AVF with L.A.D
lead 1 is upward and AVF is downward
what is the normal angle for AVL
-30
what is the normal angle for lead 1
0
what is the normal angle for AVR
+30
what is the normal angle for lead II
+60
what is the normal angle for AVF
+90
what is the normal angle for lead III
+120
how is the rotation described if the ratio of the R:S ratio changes from <1 to >1 after V4 (horizontal plane)
leftward axis rotation
how is the rotation described if the ratio of the R:S ratio changes from <1 to >1 at or before V2 (horizontal plane)
rightward axis rotation
how is the rotation described if the ratio of the R:S ratio changes from <1 to >1 after V2 and at or before V4 (horizontal plane)
normal
what happens if in the horizontal plane the R:S ratio starts <1 and stays <1
leftward axis rotation
what happens if in the horizontal plane the R:S ratio starts >1 and stays >1
rightward axis rotation
what happens if in the horizontal plane the R:S ratio starts >1 and becomes <1 by V6
leftward axis rotation
