EKG Flashcards
Graphical recording of summated electrical activities of heart by surface electrodes?
electrocardiogram
machine that records ECG
electrocardiograph
how do you make a electrocardigraphic lead?
Positive electrode from positive pole and negative electrode from negative pole will pick up electrical activities produced by heart
how many leads are there in total?
12
in what two major groups are leads divided into?
Limb Leads
Unipolar Chest Leads/Precardial Leads
what are the 2 groups of limb leads?
3 are bipolar limb leads
3 are augmented unipolar limb leads
what are the 3 are bipolar limb leads?
Lead I, Lead II, Lead III
what are the 3 are augmented unipolar limb leads?
aVR, aVL, aVF
what do augmented unipolar limb leads do?
Augment electrical potential to match electrical potential of bipolar limbs
limb leads will look at electrical activity of the heart from what view?
frontal plane
Unipolar Chest Leads/Precardial Leads will look at the electrical activity of the heart from what view?
horizontal plane view
what are the Unipolar Chest Leads/Precardial Leads ?
V1
V2
V3
V4
V5
where are the Unipolar Chest Leads/Precardial Leads placed on the body?
o V1: 4th ICS, right sternal border
o V2: 4th ICS, left sternal border
o V3: between V2 and V4
o V4: 5th ICS, midclavicular line
o V5: anterior axillary line
where do you place limb leads (normal and augmented) in the body and at what angle?
o Lead 1: right arm is negative; left arm is positive; angle of orientation is 0 degrees.
o Lead 2: right arm is negative; left leg is positive; angle of orientation is 60 degrees.
o Lead 3: left arm is negative; right leg is positive; angle of orientation is 120 degrees.
o aVL: left arm is positive, all other limbs are negative; angle of orientation is -30 degrees
o aVR: right arm is positive, all other limbs are negative; angle of orientation is -150 degrees
o aVF: legs are positive, all other limbs are negative; angle of orientation: 90 degrees
what is the Anatomical Group of V1 and V2?
Septal
what is the Anatomical Group of V3 and V4?
Anterior
what is the Anatomical Group of Lead 1, aVL, V5, V6?
lateral
what is the anatomical group of Lead II, Lead III, aVf ?
Inferior
what is the anatomical group of aVR ?
none
what is P wave?
when SA node generates impulse – spreads to atria,
what is QRS?
what is Q?
what is R?
what is S?
depolarization of ventricles
Q = septal depolarization
R = depolarization of apex
S = depolarization of base of heart
Which ion conductance is maximum during QRS?
sodium
After ventricular depolarization, ventricles will remain how? why?
depolarized before they get repolarized; no potential is recorded; corresponds to plateau phase of ventricular action potential.
what is T wave?
Ventricular repolarization
T wave represents which phase of action potential of fast cells?
corresponds to Phase 3 [point directly after T wave]
Which ion conductance is maximum during T wave?
Potassium conductance
which part of the heart repolarizes first?
base
what is the last part of the heart to depolarize?
base
how long does PR Interval last?
.1-.2 segs
in ecg, from where to where is PR Interval?
m beginning of P wave to beginning of QRS
what is the PR interval?
time duration for impulse to go from SA node to ventricular muscle
what happens if impulse takes longer to get through AV node?
PR interval is prolonged and PR segment is prolonged with delayed conduction
what can cause the PR interval to be prolonged as well as the PR segment leading to delayed conduction ?
parasympathetics can cause a negative dromotrophic
Ex: Beta blockers and calcium channel blockers can also delay conduction through AV node = decreases velocity of conduction
what does it mean if the PR interval is Greater than 0.20 sec ?
prolonged PR interval = 1st degree heart block
from where to where does the PR segment extend?
between the end of P wave to beginning of QRS
how do you calle the time interval between the PR segment?
Time interval is called AV Delay
what does AV delay mean?
time taken by impulse to get through AV node, represents AV nodal conduction
what are Septal Q Waves?
produced by depolarization of interventricular septum
how long does septal Q waves last?
normal duration is less than 0.04 seconds or less than 25% of the amplitude of R wave
what does it mean if 25% or more in amplitude of R wave?
pathological Q wave seen in myocardial infarction
what if you see a septal Q wave greater than 0.4 seconds in width [one small square] and/ greater than 2mm in depth [two small squares]?
pathological Q wave, seen in myocardial infarction
how long does the QRS Interval last?
lasts 0.08 – 0.10 seconds
how do we indentify the QRS interval?
from beginning of P wave to end of S wave
what does the QRS interval mean?
indicates duration of ventricular depolarization.
how long does the QT Interval last?
lasts 0.32 – 0.43 seconds normally
how do we identify the QT interval?
interval from beginning of Q wave to end of T wave;
what is the QT interval?
represents ventricular depolarization and ventricular repolarization.
how do we identify the ST Segment?
from the end of S wave to beginning of T wave,
what phase of action potential of fast cells in heart does ST segment correspond to?
to Phase 2 of action potential [plateau]
when do we see ST segment elevated?
in myocardial infarction
when do we see ST segment depressed?
angina
Which ion conductance is maximum during ST segment?
Calcium conductance.
what is the ST segment?
End of ventricular depolarization to start of ventricular repolarization
what is T Wave: ?
ventricular repolarization
what is the normal ecg Number of small squares/minute ?
1500 small squares or mm/min
what is the normal number of large squares/minute?
300 large squares/min