EKG Flashcards
What is an EKG?
An electrocardiogram (ECG or EKG) is a recording of the electrical activity of the heart over time produced by an electrocardiograph, usually in a noninvasive recording via skin electrodes.
EKG word origin
electro, because it is related to electrical activity
cardio, Greek for heart, (German Kardio)
gram, a Greek root meaning “to write”.
5 components of basic EKG
RATE RHYTHM HYPERTROPHY INFARCTION AXIS
Rate is it what or what?
bradycardia or tachycardia
What sets the rate at which the heart beats?
SA Node - Sinus Rhythm NORMAL SINUS Rhythm
Right Ventricular Hypertrophy -
large R wave in V1
Left Ventricular Hypertrophy -
S in V1 and R in V5 > 35 mm
ST segment elevation
- means acute or recent
ST segment depression >
2mm older injury, ischemia
Axis – refers to
the diection of depolarization wave
What is an EKG Used for?
The display indicates the overall rhythm of the heart and weaknesses in different parts of the heart muscle.
What is the best way to measure and diagnose abnormal rhythms of the heart?
The best way to measure and diagnose abnormal rhythms of the heart through EKG
particularly abnormal rhythms caused by
damage to the conductive tissue that carries electrical signals
abnormal rhythms caused by levels of
dissolved salts (electrolytes), such as potassium, that are too high or low.
In myocardial infarction (MI), the EKG can identify
damaged heart muscle.
What can’t the EKG do?
It can only identify damage to muscle in certain areas, so it can’t rule out damage in other areas.
The ECG cannot reliably measure
the pumping ability of the heart.
Since an ECG cannot reliably measure pumping ability of the heart, what should be used?
ultrasound-based (echocardiography)
nuclear medicine tests
The electrical impulse starts in the _____ ______and moves through _____ to the ______ _______
It then moves through the left bundle branch (LBB) and right bundle branch (RBB) and finally to the purkinje fibers to contract the ventricles.
SA node
the atria to the AV node.
Bachman’s bundle electrically connects
the left and right atria.
There is a pause at the __ _____ when? the _____ the ____ __ ___
AV node before the signal hits the Bundle of His (pronounced hiss).
How many electrode placed on the body and where? What are those leads called?
10 electrodes placed on the body . . . Yet called a 12 lead?
3 limb leads (I, II, III) 3 augmented limb leads (aVR, aVL, aVF) 6 chest leads \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ 12 leads
Why is it called 12 lead when their are only 10 leads?
*The EKG machine does the work to “create” the other leads, you just put the 10 stickers on.
What is a lead?
a combination of electrodes that form an imaginary line in the body along which the electrical signals are measured.
Frontal Plane View
Leads I, II, III \+ Augmented limb leads aVR, aVL, aVF \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Frontal plane view of the heart
Sensing the heart’s electrical activity
via electrodes (contacts placed on the surface of the body )
For EKG, anatomical orientation is from the
subject’s perspective
right = left
The basic four limb electrodes:
electrical polarity:
neutral or ground
negative
positive
(manipulated by the EKG machine)
polarity
Lead I goes
toward left arm
Lead II goes
toward left foot
Lead III goes
(down & rightward)
Leads I, II, & III together create what
“Einthoven’s triangle”
“Einthoven’s triangle” is what kind of triangle whose vertices lie to
an equilateral triangle whose vertices lie at the left and right shoulders and the pubic region and whose center corresponds to the vector sum of all electric activity occurring in the heart at any given moment, allowing for the determination of the electrical axis.
Einthoven’s triangle is approximated by the
triangle formed by the axes of the bipolar electrocardiographic (ECG) limb leads I, II, and III.
The center of the Einthovens’s triangle offers
a reference point for the unipolar ECG leads.
Plus “augmented” leads, e.g.
aVR (augmented vector right)
Plus “augmented” leads, e.g.
aVL (augmented vector left
Plus “augmented” leads, e.g.
aVF (augmented vector foot)
Chest leads
V1 - V6
provides cross sectional view of the heart
horizontal plane
Limb leads
I, II, III
aVR, aVF, and aVL
Limb Lead I
I, from the right arm (-) toward the left arm (+)
II, from the right arm toward the left leg
Limb Lead II
LIMB LEAD III
III, from the left arm toward the left leg
aVR,
augmented lead toward the right (arm)
aVL,
augmented lead toward the left (arm)
aVF,
augmented lead toward the foot
aVR is approx opposite of
of I and should essentially mirror the shape of I vertically
Chest leads –
V1 through V6, starting over the right atrium with V1, and placed in a semi-circle of positions leftwards, to the left side of the left ventricle
The normal progression of muscular contractions, hence, electrical activity, travels from
the upper right part of the atria downward and leftwards to the ventricles, with the left ventricle being the strongest.
Various combinations of limb leads and chest leads taken together provide
a three-dimensional view into the electrical activity and workings of the heart for anyone who knows how to read an EKG.
Interpreting the view from an electrode
An approaching train of muscle fiber depolarizations (or repolarizations moving away)is seen as an upward trace on the recording
(opposite movement = downward trace)
the normal average direction for the heart’s electrical activity is from
the upper right, in the right atrium, to the lower left. (like cpr)
Typical waves of an EKG.
PQRST
P wave
ATRIA: depol-pause-repol
atrial repolarization is obscured by
ventricular depolarization
VENTRICLES: depol-pause-repolarize
QRS complex
Pacemakers of the Heart
SA Node -
AV Node -
Ventricular cells -
SA NODE
Dominant pacemaker with an intrinsic rate of 60 - 100 beats/minute.
AV Node
Back-up pacemaker with an intrinsic rate of 40 - 60 beats/minute.
Ventricular cells
Back-up pacemaker with an intrinsic rate of 20 - 45 bpm.
Ectopic Focus (foci)
An excitable group of cells that causes a premature heart beat outside the normally functioning SA node.
Acute occurrence of ectopic focus is usually
non-life threatening, but chronic occurrence can progress into arrhythmia.
In a normal heart beat rhythm the SA node usually suppresses
the ectopic pacemaker activity due to the higher impulse rate of the SA node.
However, if there is a malfunctioning SA node
it’s inactivity allows the ectopic pacemakers to generate their rhythm
How to analyze EKG
Step 1: Calculate Heart rate. Step 2: Determine regularity. Step 3: Assess the P waves. Step 4: Determine PR interval. Step 5: Determine QRS duration.
Step 1: Determine HR
Heart rate (bpm)
Find an R wave on a heavy black line
Count the number of 1mm lines between two R waves
Divide 1500 by the number of 1mm lines between 2 R waves
Need to determine rate quickly to assess presence of abnormalities
Tachycardia, bradycardia
Step 2: Determine regularity
Look at the R-R distances (using a caliper or markings on a pen or paper).
Regular (are they equidistant apart)? Occasionally irregular? Regularly irregular? Irregularly irregular?
A variety of factors affect heart rate including:
PR Interval – comprises the time period from the onset of atrial depolarization (beginning of P wave) until the onset of ventricular depolarization (beginning of QRS complex) – normal = 0.12 – 0.20 seconds or 3-5 little boxes. A substantial portion of this time period is taken up by delay in AV node; also includes the bundle and bundle branches
QRS complex normal duration = no more than 0.10 second or 2.5 little boxes
(if this takes longer usually means some sort of intraventricular conduction delay (bundle branch block)
age (declines with age)
gender (females generally have higher resting heart rates)
physical stature (small animals have higher heart rates)
emotion (stress can elevate HR)
Type of food consumed (caffeine increases HR)
Body temperature (rise in temp increases HR)
Environmental factors (smoking increases heart rate)
Highly trained endurance athletes (have low resting HRs)
Some abnormalities occur naturally, while others may be more serious, such as sick sinus syndrome, bundle branch block and may require medical therapy.
We can see P waves for each Q wave, but some QRS complexes are closer together than others.
Using ECG calipers, you can measure the first QRS then spin the points. You’ll notice they gradually increase.
Although it is not shown, the rate will return to normal; this fluctuation usually occurs with breathing patterns.
The rate is 8*10 here so it is sinus and within normal range.
This is mostly due to vagus (CNX) nerve innervation, which controls the parasympathetic system.
Healthy and young individuals have this and it is considered normal.
Loss of sinus arrhythmia may signify the beginnings of heart failure.
s
Step 3: Assess the P waves
Normal P waves with 1 P wave for every QRS Are there P waves? Do the P waves all look alike? Do the P waves occur at a regular rate? Is there one P wave before each QRS? Interpretation?
Step 4: Determine PR interval
Normal: 0.12 - 0.20 seconds.
(3 - 5 boxes)
Step 5: QRS duration
Normal: 0.04 - 0.12 seconds.
(1 - 3 boxes)
Normal Sinus Rhythm
Rate 90-95 bpm Regularity regular P waves normal PR interval 0.12 s QRS duration 0.08 s
Normal Sinus Rhythm (NSR) cause
Etiology: the electrical impulse is formed in the SA node and conducted normally.
This is the normal rhythm of the heart; other rhythms that do not conduct via the typical pathway are called arrhythmias.
NSR
arrhythmias
other rhythms that do not conduct via the typical pathway
NSR Parameters
Rate 60 - 100 bpm Regularity regular P waves normal PR interval 0.12 - 0.20 s QRS duration 0.04 - 0.12 s
Any deviation from above is sinus tachycardia, sinus bradycardia or an arrhythmia
Ways the ECG can change include: for MI
ST elevation & depression
Significant Q wave = for MI
Necrosis
FOR MI
ST elevation =
Injury
FOR MI
T wave inversion =
Ischemia
Myocardial Infarction (MI) An old MI
(“age-indeterminate”) will likely have significant Q waves as well as T wave inversion.
Left Ventricular Hypertrophy
The QRS complexes are very tall (increased voltage)
Why is left ventricular hypertrophy characterized by tall QRS complexes?
As the heart muscle wall thickens there is an increase in electrical forces moving through the myocardium resulting in increased QRS voltage.
Left Ventricular hypertrophy
S wave in V1 (mm)
+ R wave in V5 (mm)
——————————
Sum is > 35mm = L.V.H.
depolarization of the Bundle Branches and Purkinje fibers are seen as
the QRS complex on the ECG
a conduction block of the Bundle Branches would be
reflected as a change in the QRS complex.
With Bundle Branch Blocks you will see two changes on the ECG:
QRS complex widens (> 0.12 sec).
QRS morphology changes (varies
Why does the QRS complex widen?
When the conduction pathway is blocked it will take longer for the electrical signal to pass throughout the ventricles.
What QRS morphology is characteristic? bbb
For RBBB the wide QRS complex assumes a unique, virtually diagnostic shape in those leads overlying the right ventricle (V1 and V2).
Graded Exercise Test
GXT
GXT what is it is?
A maximal (or submaximal) exercise test with planned and controlled increases in intensity.
What is the GXT used for?
Diagnose overt or latent heart disease
To evaluate cardiorespiratory functional capacity
To evaluate responses to conditioning or rehabilitative programs
To increase motivation for entering and adhering to exercise programs
Dt3
When to use GXT?
Older men (45 years) and women (55 years)
Individuals of any age with moderate risk (two or more CHD risk factors)
High – risk individuals with one or more signs/symptoms of cardiovascular/pulmonary disease
High – risk individuals with known CV, pulmonary, metabolic disease
Maximal test before (GXT)
starting a vigorous (>60%VO2max
When not to use GXT?
When a person meets any absolute contraindications for the test
OR
Relative contraindications (Situation specific)
Use Submaximal Exercise Test for: GXT
low – risk individuals
Moderate – risk individuals,
if starting a moderate exercise program
(40 – 60%VO2max)
Contraindications to Clinical Exercise Testing abosulute
A recent significant change in resting EKG Unstable angina Uncontrolled cardiac dysrhythmias Symptomatic severe aortic stenosis Uncontrolled symptomatic heart failure Acute pulmonary embolus or pulmonary infarction Acute myocarditis or pericarditis Suspected or known dissecting aneurysm Acute systemic infection
Recent EKG suggesting significant ischemia, recent MI (within 2 days) or other acute cardiac event
Uncontrolled cardiac dysrhythmias causing symptoms or hemodynamic compromise
Heart failure - is a condition that can result from any structural or functional cardiac disorder that impairs the ability of the heart to fill with or pump a sufficient amount of blood through the body
s
Common GXT Protocols Decision based on
subject/patient and purpose of the test
Common GXT Protocols names
Bruce – walk to run up a hill Balke Naughton Ellestad Modified Astrand
Bruce Protocol
- Each stage is 3 mins in duration
Patient Monitoring
Electrocardiography (EKG)
Blood Pressure
Ratings of Perceived Exertion (RPE)
Electrode Preparation Goal:
improve electrical conductivity; reduce electrical impedance
Electrode Prep Goal
Steps to follow:
Shave hair, if necessary
Remove superficial layer of skin
Oil should be removed by a fat solvent (isopropyl alcohol)
Abrade with fine-grain emery paper, gauze, other appropriate material (I.e. scrubby pad)
Electrode Preparation reduce
Reduce excessive motion artifacts that result from movement of chest electrode during exercise
reduce oily skin
tincture of bezoin (for excess sweat) increases the stickiness of electrodes
Electrode Preparation
Obese individuals
may need to move V4 and V5 to sixth intercostal space
Blood Pressure during GXT
You now know how to do this
Listen for phase IV
Diastolic may drop to 0 mmHg
Once the subject starts to run – remove BP cuff
Not safe to take while running in the lab
Rating of Perceived Exertion
Borg, 1981
Measured near the end of each exercise stage
Test Sequence & Measurements Before Exercise
EKG tracings taken w/ patient supine, standing and standing 15sec hyperventilation
Test Sequence & Measurements During Exercise Test
HR & BP measured during each stage (typically every 2 or 3 minutes
HR & BP monitored every 1 or 2 minutes during recovery period (walking 2-3 mi/hr or 75-150 kgm/min) until HR & BP stabilize (3-5 minutes)
Attainment of Maximal Capacity
Failure of heart rate to increase with increases in exercise intensity
Venous lactate concentration exceeding 8 mmol/L
Respiratory exchange ratio (RER) greater than 1.15
Rating of perceived exertion > 17 (using original Borg 6-20 scale)
Active or passive recovery
Diagnostic purpose
– supine position immediately after exercise
ST Segment
Supine position does what?
Increases venous return, myocardial O2 demand, ventricular wall stress
Absolute Indications for Test Termination
Moderate-to-severe angina
Drop in SBP of 10 mm Hg from baseline BP despite an increase in workload, when accompanied by other evidence of ischemia
Increasing nervous system symptoms (ataxia, dizziness or near syncope)
Signs of poor perfusion
Technical difficulties monitoring EKG
Client’s desire to stop
Sustained ventricular tachycardia
ST elevation ( 1 mm) in leads without diagnostic Q waves
Ataxia –
inability to perform coordinated muscular movements
Signs of poor perfusion –
cyanosis, pallor
Relative Indications for Termination of GXT (GETP8-Box 5-2)
Drop in SBP of 10 mm Hg from baseline BP despite an increase in workload, in absence of other evidence of ischemia
Increasing chest pain
Fatigue, shortness of breath, wheezing, leg cramps, or claudication
Hypertensive response (SBP > 250 mm Hg and/or DBP > 115 mm Hg Development of bundle-branch block or intraventricular conduction delay that cannot be distinguished from ventricular tachycardia
Arrhythmias including multifocal PVCs, triplets of PVCs, heart block, supraventricular tachycardia or bradyarrhythmias
ST or QRS changes – Excessive ST depression (2 mm horizontal or downsloping ST-segment depression)
claudication
limping
General Indications for Stopping an Exercise Test - Low Risk Adults
Onset of angina or angina-like symptoms
Significant drop (20 mm Hg) in SBP or failure of SBP to rise w/increase in exercise intensity
Excessive rise in BP: SBP > 260 mm Hg or DBP > 115 mm hg
Signs of poor perfusion: light-headedness, confusion, ataxia, pallor, cyanosis, nausea or cold and clammy skin
Failure of heart rate to with increasing intensity
Noticeable change in heart rhythm
Subject requests to stop = volitional exhaustion
Physical or verbal manifestations of severe fatigue
Failure of testing equipment
