lab 1: ECG analysis LAB EXAM Flashcards
explain why the heart is the most simple organ
It secretes no hormones, breaks down no enzymes, detects no external stimuli, and neither adds nor withdraws substances from the blood. It is a pump
where does innervation of the heart occur
medulla
what happens to the heart, resp and mettabolism during sleep
they are maintinaed at effieicent minimal levels
what is the muscle layer of the heart called
myocardium
what is the function of the contractions of the myocardium
Contractions of the myocardium force blood in and out of the chambers on a
two-stage journey through the heart
what is the functiuon of the valves in the heart
regulate the flow of blood into and out of the proper chambers, opening and close with each contraction of the myocardium
where does co2 saturated blood enter the heart
rigth atrium
how does co2 saturated blood enter the right atrium
VENA CAVA
after blood is in the right ventricle, where does it get pumped out through
thrpoug h the pulmonary artery
what kind of blood does pulm artery carry
deoxy blood
where do pulmonary arteries carry blood and why
The pulmonary artery carries blood to the lungs, where it exchanges its carbon dioxide for oxygen inhaled by the lungs;
carbon is exhales
how does new oxygenated blood get to the heart
pulm veins
where do pulm veins carry oxy blood
into the left atrium
what is the function of the atrium
reservoirs for the ventricles, assuring constant flow of blood through the heart and acting as a ventricular priimer
(the atria’s pumping serves to adequately fill the ventricles prior to
each ventricular contraction)
aFter blood is in the left ventricle, where does it get pumped out throug h
the aorta and out into the body to carry nutrients to the body tissues
as blood gives up o2 to the tissues, what does it c=pick up along the way
co2 and returned to the heart
what is Each contraction of the myocardium preceded by
an action potential generated by specialized cells in the sinoatrial (SA) node, l
where is action potential generated in the heart
at the sinoatrial node
where is the SA node locatied
in the right atrium near the Sup vena cava
All myocardial cells are tightly joined together via BLANK, which are unique to the heart.
intercalated discs
what is the fucntion of the intercalated disks joining the myocardial cells
The intercalated discs have a lower resistance to electrical conductivity than the outside of the myocardium, resulting in a quick propagation of the cardiac action potential from the SA node to adjacent myocardial cells
why is it good that the The intercalated discs have a lower resistance to electrical conductivity than the outside of the myocardium,
results in a quick propagation of the cardiac action potential from the SA node to adjacent myocardial cells
after the signal from the SA depolarizxes the adjacent myocardial cells, where does it travel
the depolarisation also follows an electrical pathway that leads to the atrioventricular (AV) node
where is the AV ndoe located
at the border between the atriam and ventricles along the midline of the hear t
From the AV node, where does the action potential travels
downward toward the apex of the heart via the Bundle of His, Right and Left
Bundle Branches and the Purkinje Fibres
put thsee in order ( , Right and Left Bundle Branches, SA node,
, AV node and the Purkinje Fibres, Bundle of His
SA node AV node bundle of HIS R/L bundle brances purkinje fibers
what tissue is the electrical conductive pathway composed of
composed of specialized non-contractile, highly conductive cardiac tissue that ensures the heart depolarizes and contracts in a sequential manner (from atria to ventricle), and as a coordinated unit.
why is the electrical conductive pathway composed of specialized, non contractile and highly conductive cardiac tissue
ensures the heart depolarizes and contracts in a sequential manner (from atria to ventricle), and as a coordinated unit.
as the depolarization nwave travels down the heart/pathway, waht happens to the myocardial cells
they depolarize and subsequently contract
true or false: the electrical impulses that occur at the heart do not spread throug hthe body
false,
These waves of electrical impulses, although occurring locally at the level of the heart, also spread through the body, eventually reaching the skin
what is the amplictude of voltage changes that can normally be picked up by ECg
1-2 mV
what is the function of the ECG
The ECG offers a reliable, non-invasive way of studying the integrity
of the heart’s electrical conductive system and allows for an overall evaluation of cardiac health.
what are Three words describe the heart’s electrical activity:
polarisation, depolarisation, and repolarisation
explain what the term Polarisation refers to
the heart at rest (i.e., no impulse, stimulation, contraction, nor measurable
electrical activity), awaiting a depolarising signal, normally from the SA node.
explain what the term Depolarisation means
is another word for the discharge of electrical energy that triggers the contraction. This depolarisation can be measured by the ECG
true or false: polarization can be measured by an ECG
no , only re or depolarization (when there is achagne in voltage) can be measured
what does the term repolarization mean
Repolarisation is the electrical recovery of the heart as the cells recharge
themselves and return to the polarised state, which can also be measured by the ECG.
true or false: the ECG is a measurement of the strength of myocardial contractions of the heart
NO false
what is the ECG recording
The ECG is a recording of the electrical impulses prior to the contraction and
relaxation of the myocardium
true or false: The ECG is a recording of the electrical impulses AFTER the contraction and relaxation of the myocardium
FALSE
PRIOR TO
what is the P wave/when does it occur
occurs as a result of the action potentials (the depolarization) that cause the atria to contract
=ATRIAL DEPOLARIZATION
what does the PR interval represent
the time required for the impulse to travel from the SA node to the AV node;
=time elapsed between the onset of atrial depolarisation and the onset of ventricular depolarisation.
true or false: the ventricles can contract before the atria
false, they should not
remember the atria act as ventricular primers, and therefore must depolarise, and consequently
contract, before the ventricles.
what does the QRS occur from
the QRS complex, occurs as a result of ventricular
depolarisation (i.e., the travel of the electrical impulse from the AV node through to the Purkinje network and all the myocardial cells of the ventricles)
=ventricular depolarixation
what does the ST segment represent
Termination of the QRS complex signifies that all
ventricular muscle fibres have been depolarized and are now in a refractory period, which is represented by the S-T segment (i.e., no deflection occurs
what are the 2 typical negative deflections of the QRS completex
- the Q and the S waves.
true or false: the R wave of the QRS complex should always be present even if the Q and S waves arent?
true
Q and S may be absent but The relatively large R wave within the QRS complex represents the main phase of ventricular depolarisation and is always present under normalcircumstances
what part of the QRS complex
represents the main phase of ventricular depolarisation
the R wave
what is the T wave represent
which represents the repolarisation of the ventricles as the
cells recharge themselves
what does the QT intevenal represent
The entire Q-T interval represents the amount of time elapsed between
the beginning of ventricular depolarisation and the completion of ventricular repolarisation.
true or fale: U waves are always present on ECG
false
The origin and clinical significance of the U wave are still debated, but may represent the repolarisation of the Purkinje fibers.
why is there a delay at the AV node
allows the atria to fully contract and pump blood into the ventrciels before the ventricles contract (PR intevral)
how many vectors are there in the atrium
1 vector=1 wave
how many vectors are there through the ventricles
3 vectors=3 waves (QRS)
why is atrial repolarization usually hidden
because it occurs during ventricular depolarization (large QRS) so it is hiddne by the larger electrical events that generate that
b/w impulses, what state is the heart in
polarized
when the heart is a rest and there is no electtrical activtiy within the myocardium, what happens to the ECG
the ECG has nothing to record,
the stylus (the pen on the recorder) returns to what is called the isoelectric baseline (i.e., zero-voltage line) = the baseline
6 limb ECG containts what leads
limb and augmented limb leads
how many electrodes are placed on a patient during ECG and where (general )
4 electrodes (one on each wrist and one on each ankle)
3 are recording 1 ground electrode
where is the ground electrode located
right leg
explain electrode placement for lead 1 and the image resulting
- right arm
+ left arm
=image of left side of heart
explain electrode placement for lead 2 and the image resulting
- right arm
+ left leg
=view f\of the apex of the heaert
explain electrode placement for lead 3 and the image resulting
- left arm
+ left leg
explain how augmented limb leads work
combine 2 electrtodes to get different anglese of the heart
where is the positive electrode on the aVF
on the left leg
where is the positive electrode for avR
on the right arm
where is the postive electrode for avL
on the left arm
what is the paper speed for ECG recording
25 mm/sec
1500 mm/min
how is an ECG paper divided
into small 1 mm boxes and larger 5 mm boxes
on the x axis what are the sizes and duractions of small and large boxes
small box = 1 mm = 40 ms
large box = 5 mm = 200 ms
on the y axis what are the sizes and duractions of small and large boxes
small box = 1 mm = 0.1 mv
2 large boxes= 10 mm = 1 mv
what are the 3 main assessments for analyzing the strip
1) detecting arrythmias (using the 5 step analysis)
2) signs of hypertrophy
3) assess myuocardial damage
what are some examples of arryhtmias (causes)
ectopic beats
heart block
abnomral electrial activity
if there is an icnreased workload on the heart and myocardial hypertrophy occurs, what will happen to amplitude of the ECG waves
they will increase
if there myocardial damage (ex: myocardial infarction) what can that do to the wave forms and give examples
it can alter them
ex: ST segment elevation/depressionn, eccessively large Q waves
what are the 5 basic steps of the 5 step analysis
1) determine consistence of ryhtm ( RR int)
2) Assess HR
3) assess P wave consistency (atrial)
4) assess PR interval (av node)
5) asess qrs complex (venticles)
the 5 step analysis is done on what lead
the lead with the largets (positive/upward) deflections and a clear 6 second portion
(usally lead 2)
explain the procedure for RR interval regularity
SEE notes
what is the acceptable range for RR interval regularity
Your average RR interval +-120 m
check that every value falls within the range
If you have an abnormal RR interval, what would that indicate
SA node arryhtmia (determs heeart rate rythyms)
explain the respiratory sinus arrythmia/accordion affect
When you breathe in: heart rate increases
when you breath out: heart rate decreases
this can cause spaced out and close together RR intervals but is completely normal
what is the precise method for finding HR
PAPER SPEED (1500mm/min) / av RR interval in mm
what is considered a normal HR
60-100
what is bradycardia
low HR lower than 60
what is tachycardia
h
high HR higher than 100
if someone has an abnormal HR, what can that indicate
SA node arrythmia (dictates rhytm and rate)
what is an exception for bradycardia
young, healthy maybe athletes,
\this low HR is normal
what is the quick HR method
if the RR interval is…
5 large boxes = 60 bpm (brady)
4 large boxes = 75
3 large boxes = 100 bpm (tachy)
explain how to assess P wave consistency
size/direction: make sure they are constant, upwards, and same distance from QRS
if abnormal = atrial arryhtmia (wandering ectopic pacemaker)
position: checking if the P waves are equidistance
if abnormal = av node arryhtmia
knwo the procdure for measuring PR intervantl
.
what is a normal PR interval time
120-200 ms
what is an abnormal PR internal indicate
AV node arrythmia (too quick or too slow conduction)
know the produceres forQRS complex duration
.
what is a normal QRS complex duration
less than or equal 120 ms
how to know the end of a QRS complex?
J poiint (corner, steepest return angle)
what does an abnormal Qrs complex duration indicate
ventricular arythmia
analysis for signs of hypertrophy always is measured on how many complexes
1 complex within same lead
all arrythmia measurements are taken on the x or y axis
x
all measurements for hypertrophy are taken on the y or x axis
y axis
know the steps for measuring amplitudes
1) extend baseline
2) measure P, R wavese (from bse to high point)
3) measure Q and S waves (from pbase to low point)
true or false: when reported amplidtude, there is directionality
yes (negative and postives)
when measuring atrial hypertrophy, what leads are we observign
leads 2, 3 and AVF
what is are normal p wave amplitudes
if the p waves in leads 2,3 and AVF are less than or equal to 0.3 mV
hypertorphy is present in the atria if…
If the P wave amplitude is larger than 0.3 mV in either of Leads 2, 3, or AVF
hypertrohpy is present in the left ventricle if…
If the R wave amplitude is larger than 1.4 mV in Lead 1,
If the R wave amplitude is larger than 1.2 mV in Lead AVL
when measuring left ventricle hypertrophy, which leads do we look at
leads 1 and avL
if there is abnormal values for atrial hypertrohy, what is a reason
atrial hypertrophy,
AV valves function abnormally (may be do to calcificaution)
if there abnromal left ventricualr hyperpher, what could be a cause
systemic hypertension
hypertrohpy is present in the right ventricle if.
If the R wave amplitude is larger than 0.5 mV in AVR.
AVR waves should be neg
if we are assessing right ventricular hypertrohpy, what leads are we looking at
avr
if there is abnormal values for right ventricular hypertorphy, waht is a cause
pulmonary hypertension
when assessing signs of myocardial damage, where are observations made
e in the Lead with the LARGEST upward waves (i.e., the
same lead used in the 5-step analysis). Only one complex is analysed.
At least 2 of the listed 3 criteria are required to confirm myocardial damage
what are the 3 steps to assessing signs of myocardial damage
1) look for St depression/elevation
2) look for t wave inversion
3) look at q/r ration
know how to measure ST eleveation and depression
see notes
what are some causes of ST segment changes
- Ischemia - Ventricular hypertrophy
- Infarction - Early repolarisation
- Tachycardia - Pericarditis
- Hypokalemia - Medications
what are the 3 tissues in the heart that have their own inhreent rate of breathing
SA node (72) AV node (50) Purkking (30)
why does the SA node normally :drive the eheart”
beacuse it has the fastest inherent ratee
explain heart block
However, the
ventricles can be observed beating at their inherent rate (i.e., 30 bpm) if there is a block in the normal
conduction pathway. In such a condition, the action potential ceases somewhere in its passage through
the heart
what is a common place for heart block
AV node (since passage is normally slow)
in a heart block , is interuption usually prolongued ?
the interruption of the depolarizing signal is not prolonged, as cells beyond the block develop their own pacemaker activity. In this example, either Purkinje fibers or ventricular tissue start contracting. It may take 5 to 30 sec for the tissue to “wake up”, but the heart will start beating at about 30 bpm until the normal conductive pathway is restored
what are ectopic pacemakers
These are abnormal sites of spontaneous action potentials despite the presence of normal pacemaker signals and conduction pathways
what is the cause of ectopic pacemakers
Ectopic pacemaker sites are often caused by a localized area of
damaged tissue that tends to produce extra action potentials and therefore extra, and often abnormal,
contractions. Depending on their origin and frequency, they may either be benign or quite dangerous.
are ectopic pacemakers always dangerous
no they can be benign or dangerous depending on the origin and frequency
what is the most serious type of arrythmia
fibrilation
what are fibrillations
Fibrillation appears as random contractions and relaxations in the heart muscle
why is the heart said to look like a bag of worms in fibrilation
beacuse of the writhing contractions
when the benricles are fibrilation, what happens to pumping
there is no useful pumping
what is fibrilation usually associated with
damaged myocardium due to poor blood supply (i.e., ischemia to the heart) resulting from a blockage of coronary arteries
what happens to cardiac cells if thre is poor blood supply (like after heart attack)
s. If this occurs, cardiac cells will be in a poor metabolic state, leading to abnormal conduction properties. Conduction is likely to be slowed
or even blocked through some cells
if Conduction is likely to be slowed or even blocked through some cells, what happens to the APS
This results in a random pattern of action potentials spreading
across the tissue rather than a regular wave of excitation
fibrillation in the ventricles is not dangerous ?
false, it can cause death within minutes
explain defibrillation
Defibrillation is sometimes possible by inducing an action potential in all cardiac cells simultaneously with a large electrical shock to the chest. Hopefully, after the cells repolarise, the SA node will depolarise first, as it should, and the normal pathway will be restored. Fibrillation in the atria is
not necessarily life threatening.
how many signs must be present to solidify myocardial damage
2/3 signs
explain ST depression/elevation
mark at j point and them 2mm
if there is an elevation/depression greateer than 1 mm
=abnormal (infarction, ishecmia etc)
explain T wave inversion
T wave should be same direction as R wave wave
if not= damage to tissue
explain Q/R ratio
normal ration between Q wave and R wave should be 0.25
if greater than 0.25
vector relationship has changed
