Week 3 EKG Flashcards
A physician has documented an irregularly irregular cardiac rhythm with a heart rate of 150 bpm in a chart of a patient. The BEST interpretation of this rhythm is:
Uncontrolled atrial fibrillation
The presence of a significant Q wave (one-third the size of the QRS complex) on an ECG indicates which of the following?
Previous infarction
Which of the following reasons are considered indications for a Holter monitor?
All of the above
(Evaluating antiarrhythmic therapy or pacemaker functioning, Identifying symptoms caused by arrhythmias, Describing the arrhythmias noted with activity)
Which of the following changes on an EKG BEST indicates the presence of an acute infarction?
ST-segment elevation
What is the significance of the “big boxes” on the EKG tracing?
Each big box represents 0.2 seconds
an EKG detects ___ issues and may indirectly relate to __ problems?
electrical conduction; mechanical
how much time does one small box = on an EKG?
0.04 sec
1mm
one an EKG you use time to determine:
HR and duration of certain features of the EKG
how many small boxes are in a large box on an EKG?
5
on the Y axis of the EKG was does each mm equal?
0.1mV
on the y axis of an EKG how many boxes = 1mV?
10 small boxes (10 mm) or 2 big boxes
what can the voltage measure on an EKG be used as criteria for?
ventricular hypertrophy
What does the PR interval represent?
the pause at the AV node
(time between atrial depolarization and ventricular depolarization)
after the atria depolarize and before the ventricles depolarize
what does a long PR interval indicate?
a delay or heart block
What does the QT interval represent?
The time to depolarize and repolarize the ventricles
what does the P wave represent?
atrial depolarization
what does the distance from the t-wave to the next p-wave represent?
after the ventricles have completed repolarization and before the atra depolarize
what does the ST segment represent?
after the ventricles depolarize and before the ventricles repolarize
what are the 3 times in the cardiac cycle where isoelectric condition should occur?
t-wave to p-wave
PR segment
ST segment
what is happening if all three of the areas where isoelectric condition are supposed to occur are not the same?
-an area of the heart has a different potential than another
-an area of the heart is not depolarizing normally
-an area is not repolarizing normally
what are some causes for a wandering baseline?
-poor preparation of the electrode and skin
-loose wires
-moving clothing
what is the 60 cycle interference?
devices such as elevators and overhead lights using 60 Hz wall current superimposed on the trace
what is the path of depolarization of the heart?
-impulse spread from SA node throughout both atria
-reaches the AV node; delays the spread of impulse and allows time for efficient blood flow
-travels into left and right bundle branches
-then into perkinje fibers
what is the sequence of depolarization?
-SA node
-atria
-AV node (brief pause)
-bundle of His and bundle branches
-apex of the heart
-base of the heart
normally the wave of depolarization moves ___.
down and to the left
what is upward (+) deflection?
current moving almost directly toward positive electrode
what is downward (-) deflection?
current moving away from positive electrode
what happens if movement is perfectly perpendicular to the positive electrode?
a flat line will show
what happens if movement is close to perpendicular to the positive electrode?
a small upward deflection followed by a nearly equally-sized downward deflection
what does Q represent?
1st part of ventricular depolarization
what does the PR interval represent?
pause, atrial depolarization in complete and AV impulse has not yet started
what does the ST segment represent?
ventricular depolarization is complete
what does the t-wave represent?
ventricular repolarizatoin
Which direction should the axis of depolarization be pointing and why?
down and to the left towards the muscular left ventricle which is the workhorse of the heart
what should the p-wave look like?
upright and symmetric
what does a large Q wave indicate?
disease
what on an EKG is indicative of an old MI?
a q-wave with a magnitude of greater than 1/3 of the magnitude of the QRS complex
what does the size of the R wave relative to the S wave indicate?
whether the vector is more towards the positive electrode or away from the positive electrode
what shape should the t-wave be?
upright and symmetric
what does an inverted, flat or biphasic t-wave indicate?
abnormal repolarization usually due to ischemic disease
what is an R’ wave?
a 2nd upward deflection following the r-wave
what does an R’ wave indicate?
abnormal conduction through one bundle branch (blocked)
what is a segment?
between two wave
what is an interval?
between two waves but includes a wave
the PR interval represents the time elapsed between the:
onset of atrial depolarization and the onset of ventricular depolarization
what is ST segment depression?
ST segment drawn below isoelectric line
T-wave starts below the isoelectric line and finishes on the isoelectric line
what does ST depression indicate?
ischemia
what is ST segment elevation?
ST segment drawn above the isoelectric line
the r wave begins on the isoelectric line and finishes above it
the t wave begins at an elevated position on the tracing and finishes on isoelectric liine
what does ST segment elevation indicate?
acute myocardial infarction in the area of the heart “best seen” by this lead
what is the conduction rate of the SA node?
60-100 bpm
what is the conduction rate of the AV node?
40-60 bpm
what is the conduction rate of the bundle of his?
40-60bpm
what is a pacemaker cell?
the cell that has the fastest rate of spontaneous depolarization
normally the SA node but can be AV node or ventricular cells
the AV node and some ventricular cells can become pacemaker due to:
increased automaticity of these cells
failure of faster pacemaker
how does the ANS influence the rate of spontaneous depolarization?
slowed by the release of ACh by parasympathetic nerves
accelerated by release of NE by sympathetic nerves or circulating epinephrine
what is bradycardia?
<60bpm
what is tachycardia?
> 100bpm
