Lab 1 - electrocardiography analysis Flashcards
t/f the heart is the simplest organ
true
What is assessed by the electrocardiogram (ECG or EKG)
efficiency of the heart
area of the brain where sensory stimuli are monitored, information is relayed an adjustments are made according to the physical requirements of the body
medulla of the brain
the heart is a hollow organ made of muscular tissue called _____
myocardium
what is the first leg of the journey of blood in the heart in 6 steps
- CO2 saturated blood enters the right atrium from vena cave
- blood is pumped into right ventricle
- right ventricle pumps blood in pulmonary artery
- pulmonary artery carries blood to the lungs
- exchange of CO2 and O2
- carbon dioxide is exhaled
what is the second leg of the journey of blood in the body in 5 steps
- newly oxygenated blood goes back to left atrium via the pulmonary veins
- blood enters the left ventricle
- blood is forced out through the aorta
- blood goes to the tissues to deliver oxygen and nutrients (collects carbon dioxide)
- return to the heart - cycle begins again
serves as a reservoir from the ventricles, assuring a constant flow of blood through the heart
the atria
ventricular primer
atria
where are the specialized cells in the SA node located?
in the right atrium near the superior vena cava
what joins the myocardial cells tightly together
intercalated discs
what are intercalated dics?
lower resistance to electrical conductivity than the outside of the myocardium = quick propagation of the cardiac action potential
where is the AV node located?
roughly at the border between the atria and ventricles along the midline of the heart
From the AV node, the action potential travel downwards toward the apex of the heart via ____, and ____ and _____
Bundle of His, Right and left Bundle branches and Purkinje fibers
this electrical pathway is composed of ___ (explain)
specialized non-contractile, highly conductive cardiac tissue that ensures the heart depolarizes and contracts in a sequential manner and as a coordinated unit
The voltage changes caused by the action potentials can be measured on the body’s surface and are known the ____
electrocardiogram (ECG)
The usual amplitude of the voltage changes is only about __ mV but they can easily be recorded
1-2mV
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
Electrocardiogram (ECG)
three words to describe the heart’s electrical activity
polarisation, depolarisation, repolarisation
polarisation
refers to the heart at rest, awaiting a depolarising signal, normally from the SA node
depolarisation
discharge of electrical energy that triggers the contraction
repolarisation
electrical recovery of the heart as the cells recharge themselves and return to polarised state
which 2 phases from the heart’s electrical activity can be measured by the ECG
depolarisation and repolarisation
t/f the ECG trace is a measurement of the strength of the contractions of the heart
false
what is the ecg
recording of the electrical impulses prior to the contraction and relaxation of the myocardium
what are the letters of the ECG recording
P, Q, R, S, T and U
first waveform to appear
P wave
what occurs at the P wave
occurs as a result of the action potentials (depolarisation) that cause the atria to contract
The P wave depicts (represents) what
atrial depolarisation
waveform that represents the time required for the impulse to travel from the SA node to the AV node
P-R interval
waveform that occurs as a result of ventricular depolarisation
QRS complex
what does the termination of the QRS complex signify?
signify that all ventricular fibers have been depolarized and are now in a refractory period
waveform represented by the S-T segment
refractory period
Many ECGs show two negative deflection within the QRS complex - name them
Q and S waves
t/f it is usual to see the Q or S wave absent
false
waveform that represents the main phase of ventricular depolarisation and is always present under normal circumstances
R wave
waveform that represents the repolarisation of the ventricles as the cells recharge themselves in preparation for another impulse coming down the heart’s intrinsic electrical conduction system
T wave
waveform that represents the amount of time elapsed between the beginning of ventricular depolarisation and the completion of ventricular repolarisation
Q-T interval
what is the supposed meaning of the U wave
may represent the repolarisation of the Purkinje fibers
what is sinus arrhythmia
“accordion” effect on the ECG
irregular R wave
t/f irregular R wave is always indicative of cardiac malfunction
false
what is “being in sinus rhythm and beats”
when contractions of the heart are driven by the SA node
Normal range of value for beats/min
60 to 100 beats/min
Athletes trained in endurance events can have a normal heart rate as low as ___ bpm
55 bpm
what HR is bradycardia
less than 60 bpm
what HR is tachycardia
more than 100 bpm
what is used to measure rate (ventricular depolarization)
rate of QRS complex or R wave peaks
P wave consistency
Size, direction and position of the P wave in the ECG
P-R interval duration
Measure the P-R intervals
Should be between 120msec and 200msec
QRS complex duration
Value should not exceed or equal 120 msec
t/f if any of the results of these 5 steps is abnormal, an arrhythmia can be postulated
true
signs of hypertrophy - for atria
if the P wave amplitude is larger than 0.3 mV in either Leads 2,3, or AVF
signs of hypertrophy - for left ventricle
if the R wave amplitude is larger than 1.4mV in Lead 1, or if the R wave amplitude is larger than 1.2mV in lead AVL
signs of hypertrophy - right ventricle
if the R wave amplitude is larger than 0.5 mV in AVR
t/f amplitudes smaller than the above listed cut-offs would indicate a normal heart rate
true
what are the three things analyzed in our ECG analysis?
a) detecting arrhythmias
b) signs of hypertrophy
c) assess myocardial damage
signs of myocardial damage - how to choose the wave analyzed?
largest upward waves - only one complex is analyzed
Transient changes include ___ elevation or depression
S-T segment
Persistent changes include ___ inversion and large ___
T wave, Q waves
What is a heart block
it’s when the ventricles beat at their inherent rate (about 30 bpm) because there is a block in the normal conduction pathway
Common place for heart block
AV node
What is ectopic pacemakers
abnormal sites of spontaneous action potentials caused by localized area of damaged tissue that tend to produce extra action potentials = abnormal contractions
Potentially the most serious type of arrhythmia
Fibrillation
what is fibrillation
appears as random contractions and relaxations in the heart muscle = no useful pumping of blood by the heart
where does fibrillation occurs
in the ventricles
fibrillation is associated with
damaged myocardium due to poor blood supply resulting from a blockage of coronary arteries (ex: ischemia)
t/f fibrillation in the atria is always life threatening
false, not necessarily
solution to fibrillation
defibrillation = sending one big shock through the heart to make the cycle begin normally at the SA node
