ECG III and J Point Flashcards
ECG waveform segment?
Between waves
ECG waveform interval?
Includes waves
P wave last how long?
0.08 s
P-R segment last how long?
0.08 s
P-R interval last how long?
0.16 s
QRS complex last how long?
0.08 s
S-T segment last how long?
0.12 s
T-wave last how long?
0.16 s
S-T interval last how long?
0.28 s
Q-T interval last how long?
0.36 s
Which wave is the first - (negative) wave?
Q wave
For the Q wave to be pathological, what 2 things must be present?
Must be wider than 1 box (0.04 sec)Must be 1/3 height of the R wave
The p wave represents what?
The electrical activity of the contraction of both atria
The total QRS complex represents what?
The electrical activity of ventricular contraction
Which wave will ALWAYS be positive?
The R wave
Can you have a wave that does not contain an R wave?
Yes, is a large negative deflection known an QS wave
What is the normal range of the electric axis of the frontal plane?
-30 and +110
What is the normal range of the electric axis of the transverse plane?
+30 and -30
How do you approximate the electric axis direction from a 12-lead ECG?
Find which lead has the most positive QRS deflection, this is the direction of the lead vectorYou check this by observing which lead has the most biphasic QRS complex, then see which lead is perpendicular to the axis
Deviation of the electric axis to the right means what?
Increased electric activity in the right ventricle due to increased RV mass
What causes increased RV mass?
-Chronic obstructive lung disease-Pulmonary emboli-Congenital heart Dz-Disorders causing pulmonary hypertension or cor pulmonale
Deviation of the electric axis to the left is an indication of what?
Increased electric activity in the left ventricle due to increased LV mass
What causes increased LV mass?
-Hypertension-Aortic stenosis-Ischemic heart dz-Intraventricular conduction defect
Deviation of the electric axis could result from mechanical displacement of the heart from normal position, what could cause this?
-Pregnancy-Pneumothoraxel-Spinal deformation
T OR F: The concept of the electric axis of the heart usually denotes the average direction of the electric activity throughout ventricular activation
TRUE
When determining electric axis, use 3 easy steps.
1 ) Find most biphasic 2 ) Find which perpendicular to this lead3 ) If perpendicular lead has upward deflection then electric axis +If perpendicular lead has downward deflection then electric axis -
Perfusion is based on what?
Pressure and flow
Flow is based from what?
Volume / Time
Left axis deviation (LAD) ischemic signs?
Hypertrophy from ECGTachycardia
T or F: Electrical blocks are not pathological?
TRUE
What is the avg voltage of the R wave?
1 mV
Pacing spikes from A-pacer pacemakers paces what part of the heart?
The atriaSo conduction comes from atrium and then would be normal
V-paced pacemakers show what on an ECG?
Widened QRSPacing spikes not seen
ECG use what kind of amplifiers?
Differential amplifiers Takes + and - input signals and converts to alpha output signal (+ - )(alpha = gain of the amplifier)EX : + = 3v- = 5vOutput = (+ - ) = 3 - 5 = -2 v
Why is there a RL electrode?
It acts as an electrical reference for the ECG amplifierIt improves the common mode rejection
T or F: RL is always used in ECG axis evaluation therefore can go anywhere on the body
FALSE, it is never used in ECG axis evaluation
What is CMRR?
Common mode rejection ratio
What is CMNR?
Common mode noise reduction
Can CMNR of amplifiers make up for the electrode impedance imbalance
No they cannot
What is the common interference for EKG?
60 hz
What is a high pass filter?
Rejects low frequency signals
What is a low pass filter?
Rejects high frequency signals
What is a band pass filter?
Rejects signals that are too high and too lowMost ECG filters today are band pass
What is the approximate amplitude of the ECG waveform?
1 mV
How many volts does wall electrical outlet put out?
120 V
How many volts does electrosurgery signal put out?
60 to 400 V
The ECG is highly susceptible to what other noise?
EMG muscular noise
What is amplifier gain?
The gain is the amount of amplification
What is gain equation?
Gain = Output Amplitude / Input amplitude
A gain of 10 means what?
THe output signal is ten times larger that then input signal
A gain of 0.5 means what?
The output signal is 1/2 of the amplitude of the input signal
What does a cardiotachometer do?
Device that counts the HR
What range on display get rid of EMG activity?
0.05 Hz
What range on display gets rid of 60 Hz interference?
40 Hz
What is the range of signal frequencies that detects QRS?
5-30 Hz
What is the range of signal frequencies that detects arrhythmias and ST segments?
0.05-60 Hz
Pacemaker detection will not be detected until what frequency range?
1500 - 5000 Hz
White lead color?
RA
LA lead color?
Black
Red lead color?
LL
Chest leads color?
Brown
Reference lead color?
Green
Which type of filter uses band pass and high pass filters ?
Band reject filters
AHA required frequency response for diagnostic purposes for adults?
0.05 Hz to 150 Hz
AHA required frequency response for diagnostic purposes for pediatric population?
0.05 to 250 Hz
T or F: The bovie operates at high frequencies and this is why you cannot be shocked
TRUE
T or F: The return pad is small to help prevent burns from bovie
FALSE, pad is large
What law is used when monitoring the EKG in the MRI?
Faraday’s law
Which interference will go away after giving the patient a NMB drug?
EMG interferenceFasciculation will cause much larger interference for short period of time
What is the J point?
Exactly the point at which the wave of depolarization completes passage through the heart.It contains no electrical current flow, and such by definition become zero potentialLocated at the end of the QRS complex
S-T segment starts when?
60 - 80 msec after J point
What is the std. sweep speed on monitor?
25 mm / sec
What is considered/thought to be the true isoelectric line / point?
Point between P & Q
Is 1mm of depression or 1mV or depression more significant?
1mVIf you have 1mV depression pray and call for help and then run
The most common used parameter for measuring _____________ is 60 msec post J-point?
ST segment
Other than ST segment depression or elevation, what other criteria must be met for diagnosis of infarct?
Q wave > 1/3 the amplitude of the entire QRS complex or have Width of 1mm
Which lead gives you the greatest possibility of detecting LV Ischemia when we (practitioners) are the detectors
V52nd is V4
V5 will give you what percentage sensitivity of detecting ST segment ?
75%
What two lead combination increase ST sensitivity?
V4 and V5 :::::::: 90%
What three lead combination increase ST sensitivity?
II and V4 and V5 ::::: 96%
What four lead combination increase ST sensitivity?
II , V3 , V4 , V5 ::::::: 100%
If you have ST segment elevation, what you should you always assume?
Assume Heart not getting enough O2, work to get O2 to heart
Hyper calcemia will show what on ECG waveform?
Q-T short segment
Hypocalcemia will show what on ECG waveform?
Prolonged Q-T segment
When using an esophageal ECG lead, what are you mostly monitoring?
The posterior heart, which is usually left heart
T OR F: Esophageal ECG recordings provide very little volume conduction so is very similar to electrodes placed directly on the heart?
TRUE
What are the best determinates for HR counting?
1) Arterial pressure waveform2) Pulse Ox3) ECG
Why is ECG so unreliable when it comes to counting HR?
-MIssed beats because of respiration’s-Counting more often than each beat
What wave is responsible for ST Elevation or depression?
T wave variations(hence why Peak T waves indicate the onset of ischemia)
In most pt’s, is the J point below, at, or above the isoelectric line?
At or below
Does J point elevation have any pathological implications whatsoever?
NO, nothing pathlogical
T or F: J point elevation is very uncommon in young, healthy individuals
FALSE, is very common
Look at the slide in powerpoint, but remember , if the S-T elevation is such that it makes a smiley face, then it is OK.
IF the elevation makes a unhappy/sour/upside down smiley face then it is myocardial disease
Always remember, ANY VARIATION FROM THE NORM SHOULD BE LOOKED AT AS A POSSIBLE INDICATION OF ISCHEMIA
and now good god i hate EKG.If you all want to add anything please feel free
What signal is present everywhere on the body that the differential amplified will see at both input terminals simultaneously
Common Mode Signal
When signal at both input terminals exactly the same, output will be zero is called…
Common Mode Rejection
A higher CMRR is better. True or false?
True
If one electrode impedance is high, then input signals do not appear same at amplified, thus common mode signal appears. This is known as what?
Electrode Impedance Imbalance
60 Hz interference comes from:
Electrode Impedance Imbalance
What is the signal amplitude of EEG?
0.01 to 0.1 mV
What is the 60 Hz common mode signal amplitude?
10-500 mV
What is the amplitude of a wall outlet?
120 V
What is the amplitude of an electrocautery signal?
60-400 V
What are common ECG artifacts?
Basically anything electrical like:
EMG noise Power line LIM Electrocautery MECHANICAL VENT MRI IV pump Warmers SKIN IMPEDANCE ECG ELECTRODES, CABLES
What:
Allows low frequency
Rejects high frequency
Low Pass Filter
What filter retains ST segment info?
Low Pass Filter
What filter:
Removes baseline wandering
Removes electrode half cell potentials?
High Pass Filter
What filter rejects specific frequencies?
Notch filter
An automated ST segment analyzer filters regardless of current settings. True or false?
True
What is lost when frequency is changed from 0.5 to 1.0 Hz on ECG?
ST segment
What is lost when frequency is changed to 100 to 30 Hz on ECG?
Loss of R amplitude
What information does the ECG provide well at 0.05-100 Hz? (4)
NSR
ST segment elevation
ST segment depression
BBB
