Lecture 11: Approach to Cardiovascular Disease of the Horse Flashcards
1
Q
Horses heart have a high resting vagal tone- what does that mean
A
high parasympathetic tone, little to no sympathetic tone at rest
2
Q
horses high vagal tone predisposes them to __
A
arrhythmias
3
Q
benign, vagally mediated arrhythmias should disappear during ___
A
exercise
4
Q
what is a common sample of a vagally mediated arrhythmia that should disappear with exercise
A
2nd degree AV block
5
Q
What is normal HR
A
26-50bpm
6
Q
what is max HR during exercise
A
220-240
7
Q
Horses have extensive ___branching that results in simultaneous depolarization of ___
A
purkinkje fiber branching, ventricles
8
Q
QRS complex only useful for deterring __ and ___
A
rate and rhythm
9
Q
T of F: QRS complex gives you info on size and ectopic focus
A
false
10
Q
__-___ heart sounds can be auscultated in normal horse
A
2-4
11
Q
what are the 4 heart sounds and which ones do you always hear
A
S1- AV valve closure (lub)
S2- semilunar valve closure (dub)
S3- ventricular filling
S4- atrial systole
12
Q
what is a murmur
A
abnormal heart sound
13
Q
if you have a murmur between S1 and S2 what type of murmur is it
A
systolic murmur
14
Q
if you have a murmur between S2 and S3 what type is it
A
diastolic murmur
15
Q
what 4 things do you characterize a murmur by
A
timing, shape, point of maximal intensity, intensity level
16
Q
diastolic decrescendo murmur/ aortic regurgitation is common in ___
A
older geriatric horses
17
Q
PDA is common in __
A
newborn foals
18
Q
what is a grade 1 heart murmur
A
soft and not easily heard, localized
19
Q
what is a grade 2 heart murmur
A
soft but easily heard, heard consistently over PMI
20
Q
what is a grade 3 heart murmur
A
moderate intensity, heard immediately and consistently, small area of radiation
21
Q
what is a grade 4 heart murmur
A
loud, audible over a wide area, no palpable thrill
22
Q
what is a grade 5 heart murmur
A
loud, radiating, and with palpable thrill
23
Q
what is a grade 6 heart murmur
A
loud with palpable thrill and audible with the stethoscope held slightly away from chest wall
24
Q
what are some indications for performing an ECG
A
- Murmur
- Poor performance/ exercise intolerance
- Syncope
- Weakness
- Significant electrolyte imbalances
- Unexplained bradycardia or tachycardia
25
where are the leads placed for base-apex ECG
black lead- left fifth ICS at level of olecranon
Red lead- right jugular furrow 2/3 of the way from the mandible and thoracic inlet
White lead- right shoulder
26
what do P waves indicate, and what heart sound
atrial depolarization, S4: atrial systole
27
What does QRS indicate and what heart sound
ventricular depolarizaztion, S1 AV valve closure
28
what does the T wave indicate and what heart sounds
ventricular repolarization, S2 semilunar valve closure followed by S3 ventricular filling
29
normal or abnormal- identify problems if present
Red line is 10 seconds
Normal sinus rhythm
30
normal or abnormal- identify any problems- red line= 10 seconds
Sinus bradycardia: Atrial and ventricular rats <24
31
normal or abnormal, identify any problems. Red line = 10 seconds
Sinus tachycardia. Atrial and ventricular rates= 90
32
normal or abnormal- identify any problems. Red line =10 seconds
2nd degree AV block- no all P waves followed by QRS complex
33
are 2nd degree AV blocks always pathological?
no- they may disappear with exercise
34
normal or abnormal- identify problems if any. Red line= 10 seconds
Atrial fibrillation
35
are atrial fibrillations always pathological
yes
36
normal or abnormal- identify problems if any. Red line= 10 seconds
missing complex- problem with SA node
Dx: sinus block and sinus bradycardia
37
How do you measure atrial rate on ECG
count p waves over 10 seconds then multiply by 6
38
how do you measure ventricular rate on ECG
count QRS complex over 10 seconds and multiply by 6
39
what does an echocardiography tell us/measure
1. Chamber size
2. Wall thickness
3. Valves
4. Hemodynamics
40
what are some indications for cardiac work up in athletic horse
1. Non-physiologic arrhythmia
2. Murmur that increases in intensity over time
3. 3/6 heart murmur with mitral or aortic regurg
4. 4/6 heart murmur with tricuspid regurg
5. Congenital heart disease (VSD)
6. Continuous or systolic- diastolic murmurs
7. Signs of myocardial disease
8. Signs of CHF
41
horses with what conditions (3) should not be ridden
1. Signs of CHF
2. Signs of pulmonary hypertension
3. Complex ventricular arrhythmias
42
a “lone” a-fib refers to an “a-fib” with no __
underlying cardiac disease
43
a-fib clinical signs only noted during __
strenous exercise
44
what is the likely cause of A-fib
random re-entry mechanism
45
how does a normal heart prevent re-entry mechanism
impulse generated and travels then refractory period occurs and impulse dies and another one can’t be regenerated
46
describe how re-entry occurs when the “path is longer”/heart is bigger
by the time the impulse returns to the heart, the refractory period has ended, impulse transmitted again
47
describe how re-entry occurs when an impulse travels slowly/slow heart rate
by the time the impulse returns the refractory period has ended, impulse transmitted again
48
what is the tx/protocol for atrial fibrillation
1. ECG to confirm rhythm
2. Echo to assess structure and hemodynamics
3. Cardioversion
49
what is the drug of choice for cardiac conversion during A-fib
quinidine sulfate
50
What is quinidine sulfate and how does it work
class 1a anti-arrhythmic
Blocks fast sodium channels, increase duration of action potential and lengthen effective refractory period
51
how do you administer quinidine sulfate and what dose and when do you stop
22mg/kg q2hr via nasogastric tube until
1. Conversion to sinus rhythm
2. Development of toxic side effects
3. Max 6 doses
52
what drug may be useful for short duration a-fib <2 weeks
quinidine gluconate
53
if a patients heart rate is greater than 60 with A-fib treat first with __
digoxin
54
With a-fib, digoxin is indicated to slow to slow ventricular rate < 60bpm prior to __therapy
quinidine
55
how does digoxin work
1. Positive ions trope- inhibition of Na/K ATPase- increase contractility
2. Negative chronotrope- increases vagal tone
56
valvular heart disease is secondary to __, ___, ___, __
infection, inflammation, degenerative disease, trauma
57
what are the most common organisms cultured from valvular heart disease
actinobacillus, streptococcus
58
__valve disease is the most common cause of HF in horses
mitral valve disease
59
Aortic insufficiency very common in __
older horses
60
18yr old Arabian gelding presented with depression, breathing very hard, P=64, R=48, grade 5/6 heart murmur, crackles on thoracic auscultation. The following ECG and echo were obtained- what is wrong
ECG: sinus tachycardia
Echo: ruptured chordae tendinae of mitral valve
61
what are some appropriate treatments for CHF
1. Digoxin
2. Diuretics/ furosemide
3. ACE inhibitors- benazepril
62
what are the appropriate tx for myocardial disease
1. Gastric lavage, absorbants
2. Corticosteroids
3. Antibiotics
4. Rest
5. Management of HF
63
ionospheres are commonly added to cattle feed to prevent coccidiosis, toxic to horses at __% of cattle dose
10%
64
ionophore toxicity affects what
cardiac myocytes, myonecrosis
65
ionophore toxicity decreases __ function
systolic function
66
what are some clinical signs of ionophore toxicity
weakness, sweating, colic, tachycardia, tachypnea, muffled heart sounds, arrhythmias
67
t or f: ionophore toxicity is often fatal
true
68
what is tx for ionophore toxicity
activated charcoal, supportive care
69
what are cardiac troponins
molecules of contractile mechanism in skeletal, cardiac muscle
70
troponins complex are made up of __, __, __ proteins
I, T, C proteins
71
cardiac troponins (cTnI) often measure in horses with __
myocardial damage
72
what are some causes of pericardial disease
infectious, immune mediated, neoplastic
73
what is the most common bacteria isolated in pericardial disease
actinobacillus equuli
74
what is tx for pericardial disease
pericardiocentesis, pericardial lavage, antibiotics, supportive care
75
what is prognosis for pericardial disease caused by actinobacillus equuli
guarded prognosis
76
what is tx for pericardial disease caused by actinobacillus equuli
1. Hospitalization
2. Long term antibiotics- ampicillin and rifampin
3. Supportive care
77
aortic root rupture results in ___
sudden death
78
what is classic presentation of aortic root rupture
older breeding stallion
79
aortic root rupture occurs in higher incidence in what breed
friesian horses
80
you are the owner of a successful racetrack practice. Speedy, a 4 years old thoroughbred stallion, presents with a history of decreased performance in his last few races. On your initial physical exam you find temperature of 100.2 F, respiratory rate of 20, heart rate of 52 and a heart rhythm that was irregularly irregular.
What is most likely cause:
A. Ventricular tachycardia
B. Ventricular fibrillation
C. Atrial fibrillation
D. 2nd degree AV block
C. Atrial fibrillation
81
you are called out to do a wellness visit on 28yr old Morgan gelding, Tex who spends time as a pasture ornament. In the course of your physical exam you note a heart rate of 44 and grade 2/6 diastolic decrescendo murmur at the left fourth intercostal space
Which of the following do you tell the client:
A. Its a tricuspid insufficiency, recommend an echo
B. It’s mitral valve insufficiency, recommend an ECG
C. It’s pulmonary stenosis, recommend an echo
D. It’s aortic regurgitation, recommend a recheck at next visit
D
82
dx ECG
Sinus bradycardia- every P wave followed by QRS but HR <26bpm
83
dx ECG
Sinus Tachycardia- every P wave followed by QRS, but HR >50bpm
84
dx ECG
sinus arrhythmia- RR intervals irregular, but every P wave followed by QRS
85
dx ECG
sinus block- RR interval equal to 2 normal RR intervals
86
dx ECG
atrial premature contraction- P wave occurs prematurely and followed by normal QRS-T complex
87
dx ECG
atrial fibrillation- P waves absent, f-waves present. Normal QRS but RR intervals irregular
88
dx ECG
2nd degre AV block- P wave not followed by QRS complex
89
dx ECG
Third degree AV block- no relationship between P waves and QRS, PP intervals regular. First QRS complex is escape beat
90
dx ECG
Premature ventricular contraction- no P wave before QRS. T wave is positive deflection. Short RR interval. also 2nd degree AV block following
91
Dx ECG
Ventricular tachycardia- two VPCs followed by normal P-QRS-T
92
dx ECG
Ventricular fibrillation- no normal QRS or T-waves
93
dx ECG
Muscle tremor causing sharp narrow deflections
94
dx ECG
ECG during exercise- T waves are large and in opposite polarity to QRS, P waves no longer visible as they are incorporated in preceding T waves
95
if the SA node doesn’t fire what is missing from ECG
p wave
96
if AV node doesn’t conduct what is missing from ECG
QRS
