CP LEC 3: ECG Flashcards
What are the 4 questions to ask when interpreting an ECG
Speed?
QRS Width?
P Wave?
Regular or Irregular?
What are the ECG red flags?
- ventricular rate > 120 or < 45 bpm
- A fib
- complete heart block
- ST elevation or depression
- abnormal T wave inversion
- Wide QRS width
How long is a normal ECG strip?
6 seconds
What are two ways to find the HR from a 6 second strip?
- count R waves, x 10
- count big boxes between R waves (2=150, 3=100, 4=75, 5=60)
What is atrial kick?
Normal contraction of atria to increase pressure gradient and send blood to ventricals through mitral valve
note: if HR is too fast, there is not enough time for atrial kick = decreased CO
What does the P wave represent?
Depolarization of atria
What does the PR interval represent? What does it mean if the PR interval is lengthened?
Duration of time for electricity to go from SA to AV node (Atria to ventricals)
lengenthed PR = decreased HR
What does short PR interval mean?
hyperkalemia
What does long PR interval mean?
normal delay in AV node or 1st HB, beta blockers, Calcium channel blockers, digoxin, hypokalemia, magnesium
What does the QRS complex represent
R and L ventricular depolarization
What does the T wave represent?
Ventricular repolarization
What does the QT interval represent
Time between ventricular start of depolarization and end of repolarization
If an ECG is reading with an abnormally low voltage, does this mean a problem is likely?
Yes
What is the isoelectric line?
The x=(0) in an ECG; no electrical activity in the heart.
Monitoring a Q wave is important because it can tell you….
If there was a recent MI
Q wave with MI?
Q wave will drop lower;stays depressd for long time;scar tissue -> neg defections –> do not work with pt post acute MI until ST wave goes back to normal.
The normal rythmicity of the SA node is…
60-100bpm
The normal rythmicity of the AV node, the AV junction, and the Bundle of His is…
40-60bpm
What is the normal rhythmicity of the purkinje networks?
20-40
ST elevation vs depression
ST elevation : full thickness heart muscle damage: MI
ST depression: partial ischemia, can be non stemi MI
The rate of an arythmia can tell you what?
Where its coming from based on the autorythmicity of the different heart cells
An inverted T wave could potentially indicate what 2 problems?
Myocardial ischemia or infarction
An ST segment depressed by 2 boxes could mean what
Myocardial ischemia
angia symptoms
An ST segment elevated by 2 boxes could mean what
Myocardial infarction
What is the risk associated with an ST segment being too long?
RIsk of serious ventricular arrythmias due to slow repolarization time
How many leads does a typical ECG have?
12
Limb Lead 1 goes from where to where?
From R to L (views heart form left side)
Limb Lead 2 goes from where to where?
From upper right to lower left (views from bottom left diagonal)
Note: this is why it is the most important in capturing the electrical impulse path inside the heart
Limb Lead 3 goes from where to where?
Upper left to lower left
Lead aVF goes to and from where?
From top to bottom
views from left leg looking up at heart
Lead aVR goes to and from where?
From Middle (heart) to right arm
so views from right arm looking down at heart
Lead aVL goes to and from where?
From middle (heart) to left arm
views from left arm looking down at heart
What are the “artificial leads”
These leads are calculated by combining the signals from two limb electrodes and the Wilson’s Central Terminal (an imaginary point formed by averaging the voltage of the three limb electrodes)
How many precordial leads are there? where are these placed?
6
on the chest, providing a horizontal view
V1 and V2 leads look at what?
The right side of the heart
V3 and V4 leads look at what?
Anterior heart
V5 and V6 leads look at what?
The left side of the heart
Which leads look at the inferior portion of the heart, and what artery is there?
II, III, aVF
Right Coronary Artery
Which leads look at the lateral aspect of the heart, and what artery is there?
I, V5, V6, avL
circumflex artery
which leads look at the septal wall and what artery is there?
V1 V2
left anterior descending artery
Which leads looks at the anterior portion of the heart and what artery is there?
V3 and V4
RCA
what is the normal direction of electrical activity in the heart?
electrical activity going towards a positive electrode will show what? what about if its moving towards a negative electrode?
normal is downward to the left
going towards pos electrode will show upward deflection on ecg
going to negative will show downward deflection
Leads I-III are bipolar. Where are their normal negative and positive values placed?
this is why we typically see upward deflections on ECG
A wide QRS complex indicates that there could be an arrtyhmia coming from ________
The myocardium of the ventricals
If you suspect something is wrong on an ECG what is the first thing you should do?
Check the patient
What heart rate is considered too fast?
Too slow?
above 100 or below 60
What should you do if you see something wrong on an ECG but the patient is presenting fine?
Sit the patient down and check the leads
If the ECG reads the patients heart is too fast or too slow, they will likely show symptoms of _______
Poor cardiac output
What produces the S4 heart sound?
Atrial kick against a stiff ventricular wall/hypertension
What produces the S3 heart sound?
Turbulence when filling the ventricals (particularly the left ventrical) during early diastole. Ventricular walls are too compliant (sign of stretch/insufficinecy of the ventricular wall)
When does the S3 heart sound take place?
Early diastole, Right after the closing of the aortic and pulmonary valves
When does the S4 heart sound take place?
Late diastole, just before the closing of the atrioventricular valves.
How will an ECG look coming from the right side of the heart (V1 and V2, III, aVR
ECG will be inverted because current is moving away from it (normal is down and left)
If an impulse is traveling perpendicular to an electrode it may create a _______ waveform
Biphasic
If a patient’s ECG shows no p wave, abnormal/wide/inverted QRS, and a pause after the QRS, what is that called?
PVC (premature ventricular contraction)
pause = resetting rhythm
If you have a PVC every 2nd beat what is this called?
Ventricular Bigeminy
If you have a PVC every 3rd beat, what is this this called?
Ventricular Trigeminy
If a patient has a PVC, what should you do?
You need to check their peripheral pulse to make sure their body is getting enough blood. 60-100bpm is good.
PVCs are common and not always dangerous, but they can reduce CO and cause more serious arrythmias if they happen continuously or in someone with heart disease
doublet and triplet PVC
back to back
if your patient has a triplet PVC and a HR of ___ you should sit them down and check them.
> 100 bpm –> risk for V-tach
Nonsustained v-tach
3 PVCs in a row with HR > 100
can progress to sustained ventricular PVC/V-tach
What is SVT How can you differentiate between this and V-tach?
supraventricular tachycardia - fast HR originating from the atria (SA/AV node?) goes back to the av node before ventricle
-p wave and t wave close
-narrow QRS
V-tach will show WIDE QRS and this signal orginates from the ventricles
For every 1 litre of blood tranfused a patient needs ______ of rest
30 mins
How wide is a normal QRS wave?
1.5-3 spaces
Junctional rythm usually presents as ____(fast/slow) and with a missing _ Wave. What does this suggest?
Slow with a missing P wave
Signal is not coming from SA node!
Why could P wave inversion be normal?
You’re looking at Lead III, AVR, or lead v1 v2
(anything looking at right side)
What could be a pathological cause of P wave inversion
Heart block/junctional rhythm
What causes this dip (characterized by rounded edges)
Digoxin medication
used to increase hearts contraction but decrease HR by SNS –> decreasing repolarization phase (ST segment depression)
A Q wave is normally _______ after a heart attack and 2 days later it is _______
Deep after a heart attack and 2 days later it’s deeper
Why does the Q wave change when you’ve had a heart attack?
Scar tissue from the MI blocks impulses which leads to lower current in that region
What can cause a peaked T wave?
Hyperkalemia or cardiac ischemia
How can hypokalemia effect a T wave?
Flattened T wave
(wack repolarization bc no potassium)
Inverted T waves are associated with
Cardiac ischemia
When might T wave inversion be normal?
Lead III
Lead VI adults
AVR leads
Leads V1, V2, V3 children
In what populations is T wave inversion normal?
Normal in children due to heart being smaller
Hypertrophic cardiac myopathy is associated with ________ Inversion
T wave Inversion
Note: T wave inversion also associated with raised intracranial pressure, ischemia, infarction, PE, and Bundle Branch BLock
What is an ectopic beat?
Heart beat coming from area of the heart that has lost the rhythm with the rest of the heart
Identify this rhythm
Premature ventricular contraction
If 2 PVC’s do not look the same, what can you conclude?
They’re coming from 2 different sources
What is the difference between atrial flutter and atrial fibrillation?
Atrial fibrillation is irregularly irregular ecg (single single travling in continuous loop) whereas atrial flutter is regularly irregular “sawtooth P waves” (multiple ectopic foci coming from abnormal source)
What is torsade de pointe rhythm? What is significant about this rhythm?
polymorphic Ventricular tachycardia due to prolonged QT interval
a multifocal arrythmia
twisting, weird, QRS complex
dont work your pt!
If you see a bundle branch block on an ECG what should you think?
Not lifethreatening on it’s own but it is a warning sign of future issues
A major criteria of a bundle branch block is that the QRS wave takes longer than __s
0.12 seconds
In a RBBB, you will see a deep S wave in what leads?
Which one will show an M and which will show a W?
Leads V1 and V6
V1 shows an M
V6 shows a W
In a LBBB, which lead will show an M and which will show a W?
V1 will show W and V6 will show M
describe the pattern you might see on a RBB on v1 vs v6
v1 = rSr (“M”)
v6 = “W” big inverted S wave
What is the best lead to see a left bundle branch block from?
V6
What is the best lead to see a R bundle branch block (RSR pattern) from?
V1
What kind of AV block is normal and may occur in athletes?
First degree AV block
(essentially just the heart rate slowing down normally)
A first degree AV block is when the P-R interval is ____ squares on the ECG
5
In a first degree AV block, there is a delay through the AV node, and ____ signals eventually reach the ventricals
all of the signal (Not an actual problem!)
What is the name for a type 1 second degree AV block?
Mobitz (Wenckebach)
What will you normally see in a type 1 Second degree AV block?
Longer PR intervals which leads to eventually skipping a QRS complex
What is more dangerous? A type 1 or type 2 second degree AV block?
Type 2
What is normally seen in a second degree type 2 AV block?
Randomly dropped QRS complex with no increasing PR interval
What is a third degree AV block?
complete block, atria and ventricles are not in sync, there is no relationship between P wave and QRS complex
If a patient has a Second degree type 2 or type 3 heart block what to they need in order to work with PT?
A pace maker!!!!
With a third degree AV block (AKA COMPLETE) there is a risk of __________
A-systole (no systole)
Patient’s with long term atrial fibrillation are more likely to have a ______
Stroke
If a patient has long term atrial fibrillation what medication should they be on?
Blood thinner to prevent stroke
not all blood is leaving atrium so there is risk of a clot forming
Patients with mitral valve disease may develop _____ -fib
Atrial fibrillation
Because the mitral valve is not closing and it regurgitates blood to the atrium and dilates the atrium
