EKG book..basics cont. Flashcards
A wave of depolarization moving toward a positive electrode causes a ________ deflection
Positive
A wave of depolarization moving away from a positive electrode causes a _______ deflection
Negative
The final inscription of a depolarizing wave moving perpendicularly to a positive electrode
Biphasic wave
A wave of repolarization moving towards a positive electrode causes a _______ deflection
Negative
A wave of repolarization moving away from a positive electrode causes a _______ deflection
Positive
The limb leads view the heart in which plane?
Frontal (vertical) plane
Leads II, III and aVF are _____ leads
inferior
*they most effectively view the inferior surface of the heart
The _______ surface of the heart is the anatomic term for the bottom of the heart, the portion that rests on the diaphragm
inferior
Placed on 4th intercostal space to the R of the sternum
V1
Placed in the 4th intercostal space to the L of the sternum
V2
Placed in-between V2 and V4
V3
Placed in the 5th intercostal space in the midclaviular line
V4
Placed between V4 and V6
V5
Placed in the 5th intercostal space in the midaxillary line
V6
Under normal circumstances, which lead as inverted waves?
aVR
V1 may or may not have..
R wave
By the time you get to ___, you should have an R wave
V2
R wave progression…
R wave gets bigger from V1–>V3
Lead II is almost the same of the average direction of depolarization of the entire heart..resulting in…
Tallest R amplitude
“transition lead” of QRS complex..when the complex is transitioning from being mostly negative to being mostly positive. At this phase, it is biphasic bc this lead is perpendicular
V3
Depolarization is what kind of process
Passive
Unlike depolarization, which is largely passive, repolarization requires a great deal of..
Cellular energy
T wave can have a lot of..
Variability
*when you see QRS predominately upward, the T wave will also be downward usually
Measures beginning of depolarization (QRS) to the end of repolarization (end of T wave)
QT interval
Prolonged QT interval
V tach
V fib
**life threatening!!!!
QT interval varies depending on..
Heart rate!
Fast HR= shorter QT
Slow HR= longer QT
(must look at chart w gender and HR to determine what QT duration is normal)
Defines a cardiac cycle..from beginning of depolarization to the end of repolarization
R to R interval
Normally QT interval takes up about ___% of corresponding R to R interval
40%
if under 50%, we consider normal QT interval
V1-V4 are _____ leads
Precordial/Anterior
V5, V6, Lead I, aVL are…
Left lateral leads
II, III, aVF are..
Inferior leads
Hypertrophy refers to an increase in..
Muscle mass
the wall of a hypertrophied ventricle are THICK and POWERFUL
Most hypertrophy is caused by..
Pressure overload!
When the heart is forced to pump blood against an increased resistance, as in patients with systemic hypertension or aortic stenosis..what happens?
Hypertrophy!
_______ refers to dilation of a particular chamber
Enlargement
An enlarged ventricle can hold more blood, this is typically caused by…
Volume overload
The chamber dilates to accommodate an increased amount of blood
Enlargement
Where will atrial enlargement be seen on an EKG?
P wave
Where will ventricular hypertrophy be seen on an EKG?
QRS complex
Hypertrophied myocardium demands more blood supply but it has reduced density of capillaries and therefor is more susceptible to..
Ischemia
The chamber can take longer to depolarize..the EKG wave may therefore increase in duration
Hypertrophied or enlarged chamber
The chamber can generate more current and thus a larger voltage. The wave may therefore increase in amplitude
Hypertrophied or enlarged chamber
A larger percentage of the total electrical current can move through the expanded chamber. The mean electrical vector, or what we call the electrical axis, of the EKG wave may therefore shift
Hypertrophied or enlarged chamber
3 things that can change on the EKG in a hypertrophied or enlarged chamber..
- Increase duration
- Increase amplitude
- Shift in electrical axis
The direction of the mean vector
Electrical axis
The normal QRS axis lies between which degrees?
0 and 90 degrees
We can quickly determine whether the QRS axis on any EKG is normal by looking only at leads….
I and aVF
If the QRS complex is predominately positive in leads I and aVF, then the QRS axis is…
Normal!
If the QRS complex in either lead I or lead aVF is not predominately positive, then the QRS axis is…
Not normal! (bc it must not lie between 0 and 90 degrees)
If the axis lies between 90 and 180 degrees, it is a…
Right axis deviation
If the axis lies between 90 and 180 degrees, what will leads aVF and I look like?
QRS complex will be positive in aVF
QRS complex will be negative in lead I
If the axis lies between 0 and -90 degrees, it is a..
Left axis deviation
If the axis lies between 0 and -90 degrees, what will leads aVF and lead I look like?
QRS complex will be positive in lead I
QRS complex will be negative in aVF
In rare instances, the axis becomes totally disoriented and lies between -90 and +180, this is called..
Extreme right axis deviation
leads in both aVF and I will be negative
Sustained and severe hypertension can cause L ventricle to work too hard for too long and it hypertrophies. How does this change affect the axis?
Left axis deviation
the mean electrical vector is drawn even further leftward because the electrical dominance of the L ventricle over the R ventricle increases even more
Patients with _______ _______ may have:
- downsloping ST segment depression
- T wave inversion
Ventricular hypertrophy
