Electrocardiography and Arrhythmias Flashcards
What is the normal pathway of impulse transmission through the heart?
- Starts at the SA node in the RA
- Fires throughout RA causing atrial depolarization and contraction (atrial systole)
- Impulse slows at AV node
- Rapidly conducted through Bundle of His
- Rapidly conducted through Purkinje fibers to ventricles (ventricular systole)
Match the ECG wire color to the correct location:
Red-
Green-
Black-
White-
Red - LH
Green- RH
Black - LF
White - RF
Right front leg (-) compared to left front leg (+). Which ECG lead?
Lead 1
Right front leg (-) compared to left hind leg (+). Which ECG lead?
Lead II
Left front leg (-) compared to left hind leg (+). Which ECG lead?
Lead III
What wave shows atrial depolarization?
P wave
What wave shows ventricular repolarization?
T wave
What does the QRS complex represent?
Ventricular depolarization
What wave represents LV depolarization specifically?
R wave
What wave represents RV depolarization specifically?
S wave
What does the R wave of the QRS complex represent?
Left ventricular depolarization
(Left ventricular systole/contraction)
What does the S wave of the QRS complex represent?
Right ventricular depolarization
(Right ventricular systole/contraction)
What does the PR interval represent?
Atrial depolarization and conduction through the AV node
What does the QT interval represent?
Ventricular depolarization and repolarization
What does the RR interval represent?
Time between ventricular depolarizations
(Time between 2 heartbeats)
What does the ST segment represent?
Time between the end of ventricular depolarization and the beginning of repolarization
What does the PR segment represent?
Time between the end of atrial depolarization and the beginning of ventricular repolarization
On a 25 mm/s paper speed the width of each small box is _____
0.04 s (40ms)
On a 50 mm/s paper speed the width of each small box is _____
0.02 s (20ms)
If the amplitude of the ECG paper is 10 mm/mv, the height of each small box is _______
0.1 mV
If the amplitude of the ECG paper is 5 mm/mv, the height of each small box is _______
0.2 mV
What is the 1st negative deflection after the P wave?
Q wave
What is the 1st positive deflection after the P wave?
R wave
What is the 1st negative deflection after the R wave?
S wave
What wave can be represented as a positive or negative deflection?
T wave
Calculate the HR
Paper speed: 25 mm/s
5 QRS complexes spanning 30 large boxes
5 x 10 = 50 beats/min
When the paper speed in 25 mm/s, count the QRS complexes that span 30 large boxes and multiply by 10
Calculate the HR
Paper speed: 50 mm/s
5 QRS complexes spanning 30 large boxes
5 x 20 = 100 beats/min
When the paper speed in 50 mm/s, count the QRS complexes that span 30 large boxes and multiply by 20
Varying ___ intervals = irregular rhythm
RR
What is the normal duration of the PR interval in dogs?
60-130 msec
What is the normal duration of the PR interval in cats?
50-90 msec
What is the normal duration of the QRS interval in dogs?
< 60 msec
What is the normal duration of the QRS interval in cats?
< 40 msec
Which of the following would be considered a normal duration for a PR interval in a dog?
A. 50 msec
B. 90 msec
C. 40 msec
D. 140 msec
B. 90 msec
(60-130 msec)
Which of the following would be considered a normal duration for a PR interval in a cat?
A. 60 msec
B. 100 msec
C. 40 msec
D. 120 msec
A. 60 msec
(50-90 msec)
Which of the following would be considered a wide QRS interval in a cat?
A. 15 msec
B. 35 msec
C. 45 msec
D. 25 msec
C. 45 msec
(Normal for cat: <40 msec)
Which of the following would be considered a wide QRS interval in a dog?
A. 35 msec
B. 45 msec
C. 55 msec
D. 65 msec
D. 65 msec
(Normal for dog: <60 msec)
How can you interpret a wide P wave?
left atrial enlargement
How can you interpret a wide R wave?
- Left ventricular enlargement
- Left BBB
OR - Ectopic ventricular impulse originating in the RV
How can you interpret a wide S wave?
- Right ventricular enlargement
- Right BBB
OR - Ectopic ventricular impulse originating in the LV
What is the ECG criteria for a wandering pacemaker?
- Variation in P wave amplitude (height)
- Consistent PR intervals
(often seen with Respiratory sinus arrhythmia (RSA))
T/F: Wandering pacemaker is more commonly seen in cats than dogs
False
Rare in cats, normal in resting/calm dogs
What is the ECG criteria for a sinus bradycardia?
- Normal sinus rhythm with an abnormally low HR (long RR intervals)
Primary cause of sinus bradycardia?
Disease of dysfunction of the sinus node
Ex: sick sinus syndrome
Secondary cause of a sinus bradycardia?
Increased/high vagal (parasympathetic) tone
more common than primary
Calculate the HR
- Paper speed: 25 mm/s
- 15 small boxes between consistent RR intervals
1500/15 = 100 beats/min
When the paper speed is 25 mm/s, divide 1500 by the # of small boxes between consistent RR intervals
Calculate the HR
- Paper speed: 50 mm/s
- 15 small boxes between consistent RR intervals
3000/15 = 200 beats/min
When the paper speed is 50 mm/s, divide 3000 by the # of small boxes between consistent RR intervals**
Non pathologic causes of high vagal tone?
- Sleep/rest
- Athleticism
- Brachycephalics
What is the ECG criteria for sinus tachycardia?
Sinus rhythm with an abnormally high HR (short RR intervals)
Physiologic sinus tachycardia rarely exceeds ____ bpm in dogs or ____ bpm in cats
220, 280
Secondary cause of a sinus tachycardia?
Increased sympathetic tone
(more common than primary tachycardia)
Primary cause of sinus tachycardia?
Disease or dysfunction in the sinus node
What is the pattern of sinus tachycardia on ECG?
Normal rhythm, Short RR intervals, P waves very close to T wave
Causes of supraventricular premature complex?
- Atrial dilation (MOST COMMON)
- Atrial tumor
- Metabolic diseases
- Drugs
- Age
What is the ECG criteria for supraventricular premature complex?
- No P waves
- Premature QRS
- QRS is narrow
ECG criteria for supraventricular tachycardia?
- > 3 consecutive SVPC (premature QRS)
- Narrow QRS
- Regular rhythm
ECG criteria for atrial fibrillation?
- Irregularly irregular rhythm
- No P waves, instead fibrillation waves
ECG criteria for atrial flutter?
- Saw tooth appearance
- No P waves
How can you differentiate Sinus tachycardia vs SVT vs A flutter?
- Do vagal maneuver by providing ocular pressure or a carotid sinus massage to try and increase PNS and dec HR
- If HR decreases its sinus tachycardia
- Sinus tachycardia doesn’t exceed 220 bpm in dogs and 280 bpm in cats
_________ is a fatal rhythm
Ventricular fibrillation
ECG criteria for VPC?
- Wide QRS
- QRS not associated with P wave (AV dissociation)
- QRS can be positive or neg
ECG criteria for ventricular tachycardia?
- > 3 consecutive VPCs
- Wide QRS
- QRS not associated with P wave (AV dissociation)
ECG criteria for Accelerated Idioventricular Rhythm (AIVR)?
- Same as vtach but not fast
- Wide QRS
- QRS not associated with P wave (AV dissociation)
- No P wave
Most common cause of a VPC?
Cardiomyopathies
ECG criteria for 1st degree AV block?
- Prolonged PR intervals
- Everything else normal
ECG criteria for 2nd degree AV block?
Mobitz Type 1 vs Type 2
- Not every P has a QRS
Mobitz Type 1:
- prolongation of the PR interval before the block
- PR gets longer and longer and then P wave with no QRS
Mobitz Type 2:
- No prolongation of the PR interval before the block
- Normal rhythm and then sudden P wave with no QRS
Most common cause of 1st degree AV block?
High vagal (PNS) tone
(brachycephalics)
Most common cause of Mobitz Type 1 2nd degree AV block?
High vagal (PNS) tone
(brachycephalics)
Atrial fibrillation is commonly seen in what breeds?
Giant dog breeds with a large atrium
_________ has a saw tooth appearance on ECG
Atrial flutter
DDX for a wide QRS complex on ECG?
- Ventricular premature complex
- Ventricular tachycardia
- Accelerated Idioventricular Rhythm (AIVR)
How can you interpret a TALL P wave?
Right atrial enlargement
How can you interpret a TALL R wave?
left ventricular enlargement
How can you interpret a DEEP S wave?
Right ventricular enlargement
ECG criteria in a calm dog at the vet:
- Variation in the P wave amplitude
- PR intervals are consistent
- Normal HR
Whats going on?
Wandering pacemaker
Lub - whoosh - dub
What murmur?
Systolic click
Lub-dub-whoosh
What murmur?
Gallop
Diastolic murmur heard during S3/S4
Diastolic murmur heard with the bell in a cat, what is the underlying cause?
HCM
Diastolic murmur heard with the bell in a dog, what is the underlying cause?
DCM
