Module 3: C7: ECG 1 Flashcards
Basis of ECG:
Action potentials are happening in the _______________ level
Cellular
Basis of ECG:
Phase 0 ->
P wave | QRS complex
Basis of ECG:
Phase 3 ->
ST segment and T wave
What is the type of ECG that we use in large animal species?
Base-Apex Lead
Base-Apex Lead in Large Animals:
- (-) electrode or white electrode goes on the =>
- (+) electrode or Black electrode goes on the =>
- RIGHT jugular furrow or scapular spine (“right arm”)
- LEFT apex (“left arm”)
Frontal Leads: Einthoven’s Triangle
Right arm to (-) –> Left arm (+)
Which lead is this?
Lead I
Frontal Leads: Einthoven’s Triangle
Right arm (-) –> Left leg (+)
Which lead is this?
Lead II
Frontal Leads: Einthoven’s Triangle
Left arm (-) –> Left leg (+)
Which lead is this?
Lead III
Frontal Leads: Einthoven’s Triangle
Summed left arm and left leg (-) –> Right arm (+)
aVR
Frontal Leads: Einthoven’s Triangle
Summed right arm and left leg (-) –> Left arm (+)
aVL
Frontal Leads: Einthoven’s Triangle
Summed right and left arm (-) –> Left leg (+)
aVF
Genesis of the ECG:
1. Impulse starts in the _____ node
SA
Genesis of the ECG:
2. The signal travels through atria and _____ node
AV
Genesis of the ECG:
3. Signal travels through ___________ system
His-Purkinje
Genesis of the ECG:
4. Ventricular ____________
depolarization = Increases the membrane potential
Genesis of the ECG:
5. Ventricular ____________ (T-Wave)
repolarization = Decreases the membrane potential, restoring the resting membrane potential
ECG Paper:
When using 50 mm/sec paper speed, how many seconds is each little box?
0.02 secs (20 msec)
ECG Paper:
What is the baseline of an ECG?
Horizontal line preceding P wave
ECG Paper:
What are deflections?
Waves (positive or negative)
ECG Paper:
The paper speed is represented by which axis?
X-axis
- 25 mm/sec
- 50 mm/sec
(the higher the heart rate, the higher the speed we use)
ECG Paper:
The sensitivity is represented by which axis?
Y-axis
- also called Amplitude
- 10 mm/mV
- 5 mm/mV
- 20 mm/mV
Determining Heart Rate:
Describe the Instantaneous HR Method
- Count: ____________
- Paper speed? _____
- Divide: ____________
- 42 little boxes between complexes
- 25 mm/sec
- 1500/42 = 36 bpm
If paper speed is 50 mm/sec then take 3000/# little boxes
Determining Heart Rate:
Describe the Average HR Method
- Paper speed? 25 mm/sec
- Count amount of time: 3 or 6 seconds (the more seconds you count, the more representative is going to be)
- Count number of complexes in that time: 2
- Extrapolate to 1 minute: _____________
2 complexes in 3 seconds, 3 seconds x 20 = 60 seconds; 2 x 20 = 40 bpm
(T/F) When referring to a regular vs irregular rhythm, it means that normal vs abnormal
False
- perfectly spaced R to R intervals
- Premature beats? Pauses? are there any repetitive patterns?
Sinus rhythms: Normal sinus rhythm
Fill in the blanks of the Normal Ranges for the following species:
1. Dogs: _____ - _____ bpm
2. Cats: _____ - _____ bpm
3. Equine: _____ - _____ bpm
(must know this)
- 60 - 160
- 140 - 240
- 35 - 50
Sinus rhythms: Definition
- Very common and normal in large animals and dogs (abnormal in Cats -> high sympathetic tone in hospital)
- Associated with variable vagal tone
- Often associated with respirations (i.e. respiratory sinus arrhythmia)
- Inspiration: faster
- Expiration: slower
Sinus arrhythmia
Sinus rhythms:
In combination with Sinus arrhythmias, we can have a “Wandering pacemaker” which is …
- Gradual change in the morphology of the P waves
- Often associated with RSA (respiratory sinus arrhythmia) and high vagal tone
- Shifts in the pacemaker from within the sinus node
(T/F) Sinus arrhythmia is normal in cats
False, NEVER normal in cats, look for cause of high vagal tone
Sinus rhythms: Sinus tachycardia
- “warm up” and “cool down”
- Sometimes the P waves are buried in the T waves
What would be considered tachycardia for the following species?
1. Dogs: > ________ bpm
2. Cats: > ________ bpm
3. Equine: > ________ bpm
- 150/160
- 220
- 70
Sinus rhythms: Sinus bradycardia
What would be considered bradycardia for the following species?
1. Dogs: < _______ bpm
2. Cats: < _______ bpm
3. Equine: < _______ bpm
- 60
- 140
- 35
Definition:
Average direction of electrical potential generated by the heart during the cardiac cycle
Mean electrical Axis (MEA)
Mean Electrical Axis:
What is the normal range in a cat?
0-160 degrees
Mean Electrical Axis:
What is the normal range in a dog?
45-100 degrees
What is the most common lead we would be looking at?
Lead II
Determining MEA:
Describe the Simplified approach.
- Look at your ECG leads (Ideally 6 leads)
- Look at the direction the QRS in each lead
- Starting with the most positive and most negative - Envision these against Einthoven’s triangle
- Determine the general direction of electrical activity
Determining MEA: Simplified approach
For normal axis:
- QRS is usually _______ (neg/pos)
- II, III, avF
- QRS is either isoelectric or positive in lead ___
- QRS should be _______ (neg/pos)
- avR
- QRS is either isoelectric or negative in _____
- Positive
- Lead I
- Negative
- aVL
What can it mean when you have axis deviation?
- Conduction abnormality
- Cardiac remodeling
- Deep S waves in leads I, II, aVF (negative complexes)
- Positive QRS in aVR (may be positive in III)
- Possible causes: right ventricular enlargement, right bundle branch block
What axis deviation is this?
Right axis deviation
- Lead I & aVL are tallest (usually lead II & aVF are tallest)
- Possible causes: Left bundle block, Left ventricular enlargement
What axis deviation is this?
Left axis deviation
Atrial Enlargement:
What are we seeing with Right atrial enlargement?
Tall P waves (P-pulmonale)
Atrial Enlargement:
What are we seeing with Left Arial enlargement?
Wide P waves (P-mitrale)
Right atrial enlargement on ECG:
In the following species, what would be considered a tall P-wave in lead II?
- Dogs: > ______
- Cats: > ______
- 0.4 mV
- 0.2 mV
Left atrial enlargement on ECG:
In the following species, what would be considered a wide P-wave in lead II?
- Dogs: >_____
- Cats: >_____
- Horses: >_____
- 40 ms (> 50 ms in large/giant breeds)
- 35 ms
- 160 ms
In what species is seeing a “double hump” P-wave normal?
Horse
What would it mean if the P-waves were tall and wide?
Biatrial enlargement
- Deep S waves in Lead II
- Negative QRS in I & II
- Positive QRS in avR - Right axis deviation
- Can indicate RV hypertrophy and/or dilation
This is describing …
Right ventricular enlargement
(T/F) RV enlargement is a cause of a right axis deviation, but not all right axis deviations indicate RV enlargement
True
- Tall R-waves in Lead II
- QRS duration prolonged
- +/- Left axis deviation
- Doesn’t work for large animals
This is describing …
Left ventricular enlargement
