Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
146 Cards in this Set
- Front
- Back
|
paper speed of EKG strips
|
25 mm/sec
|
|
|
calculate heart rate on an EKG strip by
|
number of R waves in 6 seconds x 10,
or 1500 divided by the number of small boxes between R waves or 300 count - 300/by number of large boxes (300 - 150 - 75 - 60 - 50 - 43) |
|
|
each small box amplitude on the EKG strip is
|
0.1 mv
|
|
|
each small box time is
|
0.04 seconds
|
|
|
each large box amplitude is
|
0.5 mv
|
|
|
each large box on EKG strip is how much time
|
0.2 seconds
|
|
|
label and/or describe the conduction system of the heart
|
include internodal tract, sa node, av node, bachmans bundle, james fibers, bundle of kent, right bb, left bb, bundle of his, left anterior superior fascicle, left posterior inferior fascicle
|
|
|
what connects the SA node to the AV node
|
the internodal tract
|
|
|
what connects the right atria to the left atria
|
Bachman's bundle
|
|
|
what connects the right atria to the right ventricle
|
bundle of Kent
|
|
|
what connects the right atria to the bundle of his
|
james fibers
|
|
|
what connects the AV node to the bundle branches
|
the bundle of his
|
|
|
what comes out of the bundle of his
|
the bundle branches
|
|
|
what does the left bundle branch divide into
|
the left anterior superior fascicle and the left posterior inferior fascicle
|
|
|
PR interval is from
|
beginning of p to beginning of q
|
|
|
PR segment is
|
from end of P to beginning of Q
|
|
|
QRS ends at
|
the J point
|
|
|
the J point is
|
where QRS complex ends, where the line returns to baseline
|
|
|
ST segment is
|
from the J point to the beginning of the T wave
|
|
|
ST interval is
|
from the end of the QRS (J point) to the end of the T wave
|
|
|
a u wave
|
occurs after the T wave sometimes
|
|
|
the QT interval is
|
from the beginning of the Q until the end of the T
|
|
|
key concept for the EKG is
|
the EKG is a picture of the depolarization and repolarization of the cells involved in the conduction system
|
|
|
the p wave represents
|
atrial depolarization
|
|
|
1st half of the p wave represents
|
right atrial depolarization
|
|
|
2nd half of the p wave represents
|
left atrial depolarization
|
|
|
the pr interval is the
|
time for the impulse to travel through the atria to the AV junction - normal duration is.12 - .2
|
|
|
the QRS represents
|
ventricular nodal depolarization
|
|
|
normal duration of the QRS is
|
0.6 - 0.10 seconds
|
|
|
the ST segment represents
|
ventricular depolarization and contraction
|
|
|
a deviation in the ST segment
|
of more than 1 mm above or below the isoelectric line may indicate myocardial injury
|
|
|
the T wave represents
|
ventricular repolarization which proceeds from the epicardial surface to the endocardial surface
|
|
|
the QT interval represents
|
full depolarization and repolarization of the ventricle.
|
|
|
a prolonged QT is indicative of
|
a repolarization problem and may be associated with re-entry type arrhythmias
|
|
|
u waves are best seen in leads
|
V2 and V3
|
|
|
u waves are
|
"afterdepolarizations"
|
|
|
u waves are associated with
|
hypokalemia, digitalis, papillary muscle dysfunction, and is commonly seen in kids
|
|
|
u waves are sources of
|
triggered automaticity or depolarization foci that can cause arrythmias like torsades de pointes
|
|
|
1st law of electrocardiography
|
movement of the electrical impulse towards the positive electrode will result in a positive deflection on the EKG (toward the positive is a positive deflection)
|
|
|
2nd law of electrocardiography
|
movement of the electrical impulse towards the negative electrode will result in a negative deflection on the EKG (away from the positive is a negative deflection)
|
|
|
what is the reference point for the EKG
|
the positive lead
|
|
|
3rd law of electrocardiography
|
movement of an electrical impulse perpendicular to a line between the positive and negative electrodes results in a bi-phasic deflection on the EKG
|
|
|
amplitudes on the EKG reflect
|
the direction of transmission across the heart - if directly in line with leads will be a very high deflection or if off then will be smaller
|
|
|
repolarization on an EKG shows
|
opposite of depolarization - therefore repolarization towards a positive lead will cause a negative deflection on the EKG
|
|
|
the 12 lead EKG has 6 and 6 .
|
6 limb leads and 6 chest leads
|
|
|
the 6 limb leads are
|
I, II, III, AVR, AVL, AVF
|
|
|
leads I, II, and III form
|
Einthoven's triangle
|
|
|
leads I, II, and III are
|
bipolar limb leads - look at current flow as it relates to a positive and a negative electrode
|
|
|
the AVR, AVL, and AVF leads are
|
unipolar - they only look at current in relation to the positive lead and are calculated from the other 2 leads
|
|
|
AVL stands for
|
augmented voltage left
|
|
|
AVL looks at
|
the voltage vector calculation between the right arm and left leg
|
|
|
all of the limb leads look at
|
a single plane across the chest
|
|
|
lead I looks at
|
left arm to right arm
|
|
|
lead II looks at
|
right arm to left leg
|
|
|
lead III looks at
|
left arm to left leg
|
|
|
lead AVR looks at
|
the vector between left arm and left leg
|
|
|
lead AVF looks at
|
the vector between left arm and right arm
|
|
|
the hexaxial reference system is
|
the sum of all the vectors of an EKG - should lead to a value between 30 and 60 degrees normal - allows for specific mapping of the mean QRS vector.
|
|
|
axis deviation will change due to
|
hypertrophy, conduction issues, location of heart, musculoskeletal issues
|
|
|
can you draw the hexaxial reference system
|
III (120), AVF (90), II (60) along the bottom, AVL at -30, AVR at -150, I lead at 0 degrees perfectly right
|
|
|
the 6 chest leads are
|
V1 - V6 - are all positive and unipolar
|
|
|
which leads are over the right ventricle
|
V1 and V2
|
|
|
which leads are over the interventricular septum
|
V3 and V4
|
|
|
which leads are over the left ventricle and the lateral wall
|
V5 and V6
|
|
|
which lead is best for detecting an MI
|
V5 (per Gayles notes)
|
|
|
place the right arm lead at
|
base of the right shoulder against the deltoid about 2 cm below the clavicle but above the border of pectoralis
|
|
|
place the Left Arm lead at
|
the base of the left shoulder against the deltoid border about 2 cm below the clavicle but above the border of the pectoralis
|
|
|
the Right leg lead is placed at
|
Right anterior axillary line a few cm above the umbilicus
|
|
|
the left leg lead is placed at
|
the left anterior axillary line a few cm above the umbilicus
|
|
|
place V1 at
|
4th intercostal space at right sternal border
|
|
|
place V2 at
|
4th intercostal space at left sternal border
|
|
|
place V3 at
|
midway between V2 and V4
|
|
|
place V4 at
|
5th intercostal space at left midclavicular line
|
|
|
place V5 at
|
horizontal level of V4 at left anterior axillary line
|
|
|
place V6 at
|
horizontal level of V4 at left midaxillary line
|
|
|
modified V5 lead (brown) should be placed
|
over the 5th intercostal space, Left midaxillary line
|
|
|
modified V5 lead is best at
|
monitoring for changes in the ST segments in the anterior and lateral wall of the LV
|
|
|
most ST segment changes of the LV are detected by
|
lead V5 (89%) - it is the most sensitive exploring electrode
|
|
|
advantages of lead II
|
diagnoses arrhythmias and monitors inferior wall of the LV, good for inferior wall MI
|
|
|
causes of periop arrhythmias
|
inhalation anesthetics, local anesthetics, IV anesthetics, muscle relaxants, reversal agents, abnormal ABG's, abnormal electrolytes, endotracheal intubation, location of surgery, and depth of anesthesia
|
|
|
a very deep anesthetic can
|
anesthesize the brain stem and cause bradycardia and death
|
|
|
periop arrythmias usually
|
self correct and are not dangerous
|
|
|
local anesthetic toxicity frequently occurs with
|
OB patients
|
|
|
consider ordering cardiology clearance with
|
MI in past 12 months, unstable angina, recent history of CHF, new EKG changes, new onset chest pain
|
|
|
axis is
|
the orientation of the heart's electrical activity - the direction of depolarization which spreads throughout the heart
|
|
|
why does the left ventricle determine the vector through the ventricles
|
because it has the largest mass and the largest # of electrical fibers
|
|
|
normal axis deviation is between
|
0 and 90 degrees
|
|
|
left axis deviation is between
|
0 and -90 degrees
|
|
|
right axis extreme is between
|
-90 and 180 degrees
|
|
|
right axis deviation is between
|
90 and 180 degrees
|
|
|
the axis is looking at the
|
electrical activity through the heart starting at the AV node
|
|
|
if lead I is + and lead AVF is +
|
normal axis
|
|
|
if lead I is + and lead AVF is -
|
left axis deviation
|
|
|
if lead I is - and lead AVF is +
|
right axis deviation
|
|
|
is lead I is - and lead AVF is -
|
extreme right axis deviation
|
|
|
now do you determine axis deviation
|
determine if leads I and AVF are positive or negative to determine what quadrant, find lead with smallest QRS, draw a perpendicular line from that line on the hexaxial system to the quadrant to find the degree of deviation
|
|
|
accuracy of axis deviation is dependent on
|
lead placement
|
|
|
changes in axis deviation can mean
|
ventricular hypertrophy, obesity, hypertension, pulmonary hypertension, BBB, and MI
|
|
|
why does obesity cause axis deviation
|
because lead placement is so far from the heart
|
|
|
causes of left axis deviation
|
normal with diaphragm elevation, LV enlargement, inferior MI, Right sided tension pneumo, ventricular pacemaker, left anterior hemiblock
|
|
|
causes of right axis deviation
|
normal in children, right ventricle enlargement, lateral MI, left sided tension pneumo, PE, left posterior hemiblock
|
|
|
why will an MI cause axis deviation
|
scar tissue on one side of the heart will shift vector other way because scar tissue doesn't conduct electricity
|
|
|
one problem with obesity
|
cor pulmonale - RV dilates and RA dilates, right axis deviation depends on how bad the dilation is (caused by sleep apnea) - pt are difficult to ventilate
|
|
|
predisposing factors for periop MI
|
preexisiting CAD, induction and emergence from anesthesia, surgical stress, tachycardia, hypertension, hypotension, duration of surgery, bleeding, anemia, hypovolemia
|
|
|
myocardial ischemia is
|
the imbalance between coronary blood supply and demanf
|
|
|
what are of the heart is most vulnerable to ischemia
|
endocardial tissue
|
|
|
possible evidence of ischemia
|
peaked T waves, inverted T waves, and ST segment changes
|
|
|
t wave changes are best seen in leads
|
V1 - V6 since they are looking right at the ventricles
|
|
|
in an MI the T wave will typically
|
peak then decline and invert
|
|
|
a peaked T wave can indicate
|
MI, or hyperkalemia, or poor lead placement
|
|
|
and inverted T wave can mean
|
ischemia - but sometimes is nondiagnostic
|
|
|
an ST segment depression of greater than 1 mm indicates
|
subendocardial ischemia - a severe degree of myocardial oxygen insufficiency
|
|
|
possible changes in the ST segment include
|
downsloping, upsloping, depressed, or elevated
|
|
|
MI's result from
|
occlusion of a coronary artery
|
|
|
an area of infarct
|
conducts no electricity because the cells are dead
|
|
|
why does an MI lead to rhythm changes
|
because the dead tissue in the heart doesn't conduct electricity so the depolarizations take a different route
|
|
|
the triad of MI's are
|
Ischemia, Injury, Infartion
|
|
|
ischemia can be
|
reversed
|
|
|
injury can be
|
limited
|
|
|
st segment elevation > 1mm in leads II, III, and AVF indicate MI in
|
the inferior myocardium, (RCA)
|
|
|
st segment elevation > 1mm in leads I, AVL, V5, V6 indicate an MI in
|
the lateral wall (Circumflex artery)
|
|
|
st segment elevation > 1mm in leads V1-V4 indicate an MI in
|
the anterior wall (LAD)
|
|
|
st segment depression > 1mm in lead V1 indicates
|
posterior wall MI
|
|
|
V5 can pick up
|
anterior and lateral wall MI's
|
|
|
a pathological q wave signifies
|
that myocardial cell death has occurred - a completed MI
|
|
|
q waves appear
|
several hours to several days after an infarct
|
|
|
a pathological Q is defined as
|
> or = 0.04 seconds or 1/3 the amplitude of the entire QRS complex - look for BBB, exaggerated Q wave deflection
|
|
|
Q wave MI's are preceded by
|
ST segment elevation and positive CKMB results
|
|
|
non Q wave MI's are
|
more ominous - incomplete MI - less risk of initial mortality but much greater risk of reinfarction because damage is not complete - vessel occlusion was not completed
|
|
|
Tarhan et al's risk of periop MI if 0-3 months since previous MI
|
37%
|
|
|
Tarhan et al's risk of periop MI if 4-6 months since previous MI
|
16%
|
|
|
Tarhan et al's risk of periop MI if greater than 6 months from previous MI
|
5%
|
|
|
if doing surgery on pt at high risk of MI make sure to
|
document discussed risks with family and all interventions instituted in the OR to improve patient's outcome
|
|
|
the RMP of a ventricular muscle cell is
|
-90mv
|
|
|
the RMP is set by
|
potassium
|
|
|
threshold of cardiac cells is
|
-60 mv
|
|
|
threshold is set by
|
Calcium
|
|
|
if patient is hypokalemic then
|
the cell becomes hyperpolarized because more K+ leaves the cell, this makes the cells less likely to reach threshold.
|
|
|
the most common arrhythmia associated with hypokalemia are
|
PVC's
|
|
|
hyperkalemia causes
|
the K+ to increase in the cell, causing the RMP to become less negative so that the cells reach threshold easier and can fire more easily and quickly
|
|
|
hyperkalemia causes which arrhythmias
|
Vtach or Vfib because depolarizes during refactory period
|
|
|
cardioplegia solution is
|
used in open heart surgery and contains high levels of potassium
|
|
|
cardioplegia solution causes
|
the sodium gates to open then snap shut and remain in electrical arrest until the potassium levels return to normal
|
|
|
hypercalcemia causes
|
increased threshold - making it more difficult to fire
|
|
|
in a patient with hyperkalemia give
|
calcium to raise threshold to compensate for higher RMP
|
|
|
hypocalcemia causes
|
lowered threshold - excitability
|
