Flashcards in 9/3 ECG Deck (71):
pg. 37, 40, in a separate document
what are the different types of leads for an ECG?
Bipolar: Voltage recordings are made between pairs of electrodes. Unipolar: measures the potentail difference between an exploring electode and a reference electode of zero.
what are the twelve standard leads of an ECG?
Bipolar leads I,II,III; unipolar leads: aVR, aVL, and aVF.; and unipolar leads on the chest: V1,V2, V3, V4, V5, V6.
what is the right leg bipolar lead for in an ECG?
to provide a ground to cancel out "noise"
Describe einthoven triangle
the triangle of leads I,II,III that "encircle" the heart. I is top, II is right arm, III is left arm.
what are the legs and points of einthoven triange-- and the polarity of those points
I: from right shoulder to left shoulder and neg. to positive. II: Right shoulder to the stomach from neg. to positive. III: from left shoulder to the stomach neg. to positive.
what chages the size and orientation of the signal from an ECG lead
the realative motion and direction of the moving dipole. If it is in the same direction and orientation of the lead then you have a max signal and opposite direction then max neg signal and perpendicular then min signal (isoelectric)
what is isoelectric siganl in an ecg leg
when the dipole is perpendicular to the orientation of the lead. therefore a zero signal. or a net zero signal (equal parts positive and negative)
what are the two types of Unipolar leads?
Chest leads (precordial leads), and augmented unipolar limb leads .
where are the wilson's central terminal unipolar leads and what do they do?
The reference electode takes the RA LA and the LL and connects these together to get a negative reference leg.
where are the positive unipolar leads?
1,2,3,4,5,6; located from number one in the right 5th intercostal space, 2 in the left 5th IC space, then 3,4,5,6 curving down and then along the 6th rib.
what are the relative signals of the 6 positive leads of the unipolar chest leads? (consider thier positions in reference to the dipole of the heart
leads 1, and 2, are net neg, lead 3 is isotonic, leadt 4,5,6, are net positive.
what is the direction of the dipole of the heart
Down and to the left side (along the ventral septum)
what are the augmented unipolar limb leads and thier purpose
one of the leads in wilson’s central terminal serves as the + electrode and the other two are connected together as the reference electrode. (this will amplify or augment the ECG signal)
describe the normal ECG readout
the Normal ECG readout gives simultaneous readout of three leads at a time in four continuos sets. therefore all twelve leads are shown across the four sections. Then a rhythm strip is given.
what are the normal ECG signals like for the Augmented unipolar leads?
aVR is net Neg. aVL is let positive, and aVF is also net positive.
What are the leads of the Augmented unipolar limb lead system
+ on the right arm: aVR. + on the left leg: aVF. and + on left arm: aVL. In other words the “Exploring electrode is positive>
what is the timing of each large box in a ECG record?
200 msec/large box
why does the timing on an ECG record count
it gives the timing of each of the electrical signals and this can hint at arythmya
how to determing the HR in BPM
300 divided by the number of large boxes between the R-R interval waves. or 60/R-R interval in sec
what is a first degree heart block and how do we detect it
find it using the delay between the P-R interval, if this is longer than normal than there is a first degree heart block which means there is a delay in the activation of the ventricles of the heart. something happened in-between the atrium and ventricle, so probably in the AV node
what are the timeintervals for the small boxes of a ECG?
what if all of the cells suddenly depolarized what would the wave look like?
there wouldn't be one, it is the movement of the polarization that creates the charge seperation and the dipole
what is the sequence of depolarization?
the Septal depolarizaiton, apical depolarization, 3. late ventricaular depolarization, 4. compleet ventricular depolarization (no dipolel)
what happens in the septal depolarization
the first depolarization is a little on the septom between the ventricle, this is oreinted to the right and gives the Q wave
what happens in the apical depolarizatin?
the septum is depolarized and the depolarization is spreading to the ventrals and esp the left therefore the dipolle is down to the left and the R wave is generated.
what is the diple and the mean electric axis relationship
find the mean amplitude of the signal for each of the bipolar leads: take the R wave minus the Q wave, minus the S wave to ge the net dipole for the given lead.
how do we construce the mean electrical axis on the triangle.
take the net dipole from the center of the leg of the triangle and draw a perpendicular out form that point and do that for at least two legs to find the intersect where the dipole from the heart would be or the mean electrical axis
how would we go about finding the meand electricl axis without using the triangle.
colapse the legs of the triangle to the central intersect point and then then lead one is horizontal, the lead II is at angle to the right and lead three is at angle to the left. Then add in the net dipole on each lead from the intersect outward, to find the point at which to draw the perpendicular line from the lead and find the intersect of these perpendicular lines to draw the mean electrical axis for the dipole of the heart from the origin out to the intersect of the perpendicular lines.
how does the QRS change in hypertrophy patients?
the QRS is bigger!
what happens in the late ventricular depolarization?
The last part of the heart depolarizes which is the lateral superior section of the left ventricle. and therefore the dipole is to the upper left shoulder and the signal of the S wave is generated.
Describe the depolarization, the dipoles and the ECG signal for a contraction
The atrial depolarize from the SA node. the ventricles start to depolarize: 1. septal depolarization: the dipole is small and to the right (gives the Q-wave). 2. Apical depolarization down the septum and towards the left ventricle: the dipole is down and to the left (gives the R-wave). 3. Late ventricular depolarization: the last part of the heart to depolarize is usually the upper left of the left ventricle: small upward left dipole (S wave). Then complete ventricle depolarization (no dipole) flat ECG.
what happens to the ECG signal at the complete ventricular depolariztion
the signal goes to zero
what are the steps of repolariztion?
1. begining repolarization from the bottom of the heart first 2. further repolarizaiotn up the middle of the heart. 3. All cells repolarized. this results in a net dipole of down and to the left and gives the T-wave on the ECG.
what is the direction of the dipole during repolarization?
The same direction of depolorization: down to the left!
Describe the T-wave and its relation to the polarization of the cells
this is the repolarization of the heart. form the bottom up so the T-wave is the same dirrection of the QRS wave. The wave is smaller because the process is slower.
how could we get an inverted T-wave?
repolarize the cells from the top down instead of the bottom up
how do you quickly find the mean electrical axis
look at the most isoelectric lead and then guestimate how far off of isoelectric the signal is and in the positive or neg. direction. then you can get a good guese as to where the signal is.
how would right ventricl hypertrophy change the mean electrical axis?
leads to right axis deviation, meaning the dipole is moved towards the right ventricle.
how can we now if the net electrical axis is normal?
if the QRS is mainly positve in leads I and II then the mean axis is between 90 and 30 degrees positive and the net electrical axis is normal.
what is the procedure for reading an ECG?
1. determine the heart rate; 2. asses the rhythm with the rhythm strip. normal rhythm is from the SA node, and this is present if the P wave is always followed by a QRS, and every QRS has a p wave, and the orientation of the P wave is upright in leads i,II,III. The PR interval is between .12 and .2 sec. If HR is between 60 and 100. then normal!. 3. measure the intervals of QRS, QT, and PR. 4. Determine the mean electrical axis. 5. look for abnormalities in the QRS. 6. look for abnormalities in the ST segment and T wave
what if the prolonged P-R interval?
first digree heart block
what is third degree heart block
complete AV block, characterized by a slow rate of QRS waves and a complete lack of correlation between the P and the QRS waves.
what would the signs on ECG be for third degree heart block
lower heart rate per the QRS wave. and the QRS wave does not follow the rythm of the P wave. so there is no coordination between the ventricle and atrium rythm.
what is wrong with a thrid degree heart block
the secondary pacemakers are too slow and will probably need a pacemaker. low HR and low BP.
what is second degree heart block
there are P waves without a QRS wave, but other P waves have a good QRS wave associated with it. Also a slow heart rate. (the AV node is not totally conductive)
what is a PVC in the heart?
premature ventral contraction. Sometimes the lower pacemakers will fire on thier own. maybe there is a lot of sypathetic signalling or alot of epinepherin/neruoepinepherin.
why would the PVC in a heart be slower and reversed on ECG?
the depolarization of the heart is from the bottom up. and the pathway for the siganl is not as good, and therefore slower.
what is ventricular fib.
this is when the electrical activity and the contraction is very erratic.
what is sinus tachycardia?
fast heart rhythm with the normal pattern of PQRST
what is sinus bradycadrdia
when the sinus is still diriving the signal (the P wave is driving the QRS) and the heart rate is really slow.
how to identify second degree heart block
is every P followed by a QRS? if there is a P wave without a QRS then it is second degree. and the P-R interval gets longer.
how to identify long QT
look at the time interval for Q-T (40 msec per little box)
how to identify PVC
look for random slow reversed QRS.
how to identify first degree heart block
look for a long P-R interval this is fairly begnign
how to identify third degree heart block?
look for a P waves that have no correlation with any of the QRS waves.
how to detect Atrial fibrilation on a ECG?
slight quivering signal where the P wave would be . mostly the P wave is not noticalbe at all. the QRS wave may be irregualarly timed
what is Mobitz type II second degree AV heart block
there is a sudden block with no progressive increase in the PR intervals! Thi is more serious that the mobizts type I second degree block
what is a mobitz type I second degree hear block
when there are missing QRS waves, and the interval for the PR progressively lengthens between missing QRS.
what is the normal area for a mean electrical axis
-30 to +90
what is one of the problems of a atrial fibrillation patient?
the blood clots in the atrium and forms clots that can go on to cause strokes or heart attacks. (must be on blood thinners for the rest of the life of the patient.)
what is the Q-T interval?
it is from the start of the Q to the end of the T!
if yout increase the potassium flux what happens to the AP
What happens if you shorten the AP in terms of an ECG
it shortens the duration of the Q-T interval. The interval that reflects the AP.
what does sever hypercholemia look like in a ECG
very slow heart rate and slow conduction in the AV node and slow conduction in the ventricles. This led to a wide P-R interval and a wide QRS peak!
what would a premature atrial beats look like?
PACs look like a P wave coming so quickly that it gets barried in the t-wave and you have very quick heart beat in the middle of a normal rythem
what could a right quadrant shift mean for a meant electcial in ECG
righy atrium hypertrophy.
wwhat is a delta wave in an ECG?
it is a pre-excitation of the heart becasue of signal coming around to the AV node (not from the SA node) it is seen as a ramp up on the QRS wave.
What is ST segment elevation or depression and what would it indicate?
acute myocardial ischemia!! (occluded vessel); ischemic cells are depolarized during diastole (as compared to surrounding normal cells). this means that during diastole there is a constant voltage difference between the normal and ischemic regions, and this then leads to a dipole that will give different “base line value”, while at the plateau of the AP the true “base line” will be achieved and an elevated or depressed ST segment will be apparent depending on where the ischemia is!
what would a ECG look like for a pace-maker?
small spikes that indicate the points of stimulation from the pace-maker.