EKG I Lecture Powerpoint Flashcards
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CV disease is the __ cause of death and disability in the world
1
Electrocardiography (EKG/ECG) definition
Graphic recording that shows electrical activity generated by the heart muscle
Purposes of an EKG (4)
- measure heart rate and rhythm
- measure conduction abnormalities
- measure heart orientation
- find evidence of hypertrophy or damage
All for a cheap price and easy to use!
Limitations of the EKG (3)
- only shows a snapshot of about 15 seconds of time (many cardiac problems are intermittent)
- not all problems can be seen in a resting state (the idea of a stress test)
- represents electrical activity, not mechanical activity
Depolarization changes a cardiac myocyte’s membrane potential to make it less ___, allowing for…
negative, …the mechanical contraction of the myocyte
Cardiac myocyte primary function
-contraction initiated with electrical depolarization (removal of negative resting potential) coordinated from myocyte to myocyte
The heart can conduct signals ___ to ___, or via the ____ system which is much faster
cell to cell, conduction system
AV delay allows for…
…contraction of the atria before the ventricle
P wave represents…
Atrial depolarization from the SA node for about .08-.1 sec
PR SEGMENT represents…
The time in which the impulse is traveling within the AV node where conduction velocity is greatly slowed
QRS complex represents…
Ventricular depolariztiation normally about .06-.1 seconds
ST segment represents…
The period of time from which the entire ventirlce has depolarized and corresponds to the plateau phase of the ventricular action potential before ventricular repolarization occurs
T wave represents…
ventricular repolarization which typically tkes longer than the wave of depolarization
12 lead EKG
Use of 10 electrodes placed in standard locations on the body in that each show a different perspective of the heart’s electrical activity
Electrode placement of a 12 lead ekg
- V1 right 4th intercostal space sternal border
- V2 left 4th intercostal space sternal border
- V3 between V2 and V4
- V4 at the left 5th intercostal space mid clavicular line
- V5 5th intercostal space anterior axillary line
- V6 5th intercostal space mid axillary line
- 1 on left arm
- 1 on right arm
- 1 on left leg
- 1 on right leg
Bipolar lead
One positive pole and one negative pole (I, II, III)
Unipolar lead
2 poles, but negative pole is composite pole made up of signals from other electrodes (AVR,AVL,AVF)
A wave of ___ traveling ___ a positive electrode results in a ____ deflection of an EKG trace, while traveling ___ a positive electrode resuls in a ___ deflection. A
depolarization (positive charge) toward, positive, away, negative
Mean cardiac vector (electrial axis) normal direction
Downward and to the left
Lead I interprets the electrical axis upon initial depolarization as moving ___ it, and therefore creates a ___ward tick called the __ wave
toward, upward, P
PEA
Pulseless electrical activity, occurs when the patient has normal electrical conduction but a lack of a pulse often seen in cardiac arrest where the heart either does not contract or there is insufficient cardiac output to supply the organs
What is an EKG measuring?
Detects and amplifies the tiny electrical changes on the skin caused when the heart muscle depolarizes during each heart beat electrically, thru placement of leads around the body
Automaticity of the heart
Refers to ability of cardiac muscles to depolarize spontaneously without outside stimulation from nervous system at the SA node (normal pacemaker of heart), despite also receiving innervation from sympathetic and parasympathetic fibers
Conduction system pathway of the normal heart
- SA node in right atrium
- bachmann’s bundle goes to left atrium
- AV node receives the signal from the SA node and delays ventricular contraction
- AV goes thru bundle of His
- Bundle of His goes to bundle branches and then to purkinje fibers
- At the apex we see the signal then finally move to the ventricular myocardium where it contracts
PR INTERVAL represents…
The period of time from onset of atrial depolarization and onset of ventricular depolarization typically between .12-.2 seconds
PR Segment vs PR Interval
Segment is from the end of the P wave to the start of the QRS complex, interval is from the start of the P wave to the start of the QRS complex
A prolonged PR interval >___sec indicates ____
.2, first degree heart block (conduction defect in AV node)
A prolonged QRS complex >___sec indicates ___
.1 sec, bundle branch block
QT interval represents…
Timeline of both ventricular depolarization and repolarization, ranges from .2-.4 seconds depending on heart rate (have to measure corrected QT (QTc)
QTc
Corrected QT interval, calculated form to determine if the QT interval is excessively long by taking the length of it and dividing it by the square root of the RR interval (correcting for heart rate)
RR interval represents…
Interval between ventricular depolarizations
List and categorize all 12 leads of a 12 lead EKG
Limb leads (I, II, III) Augmented leads (AVR, AVL, AVF) Precordial leads (V1, V2, V3, V4, V5, V6)
Organization of an EKG
(Going top to bottom of 3 rows then right one column (/) and top to bottom of next 3 rows you get…)
I, II, III,/ AVR, AVL, AVF,/ V1, V2, V3,/ V4, V5, V6
Lead 1 2 and 3 orientation
1 - Goes from positive left hand to neg right hand
2 - Goes from positve left foot to neg right hand
3 - goes from positive right foot to neg left hand
Lead aVR AVL AVF orientation
AVR - goes form pos on right arm thru combo of left arm and left leg neg electrodes
AVL - goes from pos on left arm thru combo of right arm and left leg neg electrodes
AVF - goes from pos on left leg to combo of right arm and left arm neg electrodes
The right atrium and ventricle are ___ compared to the left
more anterior