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3. Food Animal 3 > circulatory 1 > Flashcards

circulatory 1 Flashcards

1
Q

cardio patient - what do we want to figure out about the heart problem with our clinical exam?

A

Is it a primary cardio-vascular disease?
Or inappropriate cardiovascular response?

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2
Q

cardiovascular aspects of the physical exam

A

◦ Heart
◦ Hydration (skin turgor: know normal)
◦ Edema
◦ Peripheral veins
◦ Peripheral pulses
◦ Mucous membranes

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3
Q

lactating dairy cow HR, and non-lactating

A

Heart rate range of 60-80 is for lactating dairy cow
◦ Relaxed, well socialized, non-lactating cow may well be lower
◦ Variation is normal > Interaction between sympathetic and parasympathetic tone

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4
Q

tachycardia - centrally mediated contributions

A

◦ Cortical stimulation
◦ Catecholamine release

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5
Q

tachycardia from increased peripheral demand - common reasons

A

◦ Lactation: increased metabolic rate
◦ Increased physical activity: exercise, eating

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6
Q

4 common reasons for tachycardia, very broadly

A
  • “Decrease” in blood volume (hypovolemia)
  • Severe anemia: (anemic anoxia) carrying capacity (eg. neonatal isoerythrolysis)
  • Reduced cardiac function
  • Arrhythmia
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7
Q

Tachycardia due to “Decrease” in blood volume (hypovolemia)
- types? when might we see this?

A

Absolute: blood loss, dehydration, loss of capillary integrity (burn)
<><>
Relative: change in capacitance of the system
◦ Change in venous capacitance
◦ Change in peripheral vascular beds (resistance vessels) change blood pressure
◦ Peripheral vasodilation → loss of peripheral resistance
> Toxemia/ endotoxemia/ septicemia
> Pyrexia → high metabolic rate, release vasoactive substances

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8
Q

Tachycardia due to reduced cardiac function
- what is the problem here?
- types of issues that cause this

A

Intrinsic: heart cannot respond to demands
◦ Pericardial disease: cannot fill
◦ Myocardial disease: abnormal muscle function
◦ Endocardial - especially valvular: cannot maintain fill
◦ Other diastolic (filling) problems

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9
Q

tachycardia due to arrhythmia - what might we hear?

A

◦ May or may not sound irregular

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10
Q

Bradycardia
- common reasons

A
  • Hypoglycemia
  • Decreased catecholamine levels/lack of response
  • Conservation of energy
  • Vagal stimulation
  • Hyperkalemia
  • Hypokalemia
  • Increased intracranial pressure
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11
Q

common cause of vagal stimulation leading to bradycardia

A

◦ Vagal indigestion cases

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12
Q

how does hyperkalemia lead to bradycardia?
what about hypokalemia?

A

Hyperkalemia (dysrhythmias also common)
◦ Loss of concentration gradient across cell membrane (decrease membrane potential (less
negative)
◦ Decrease available Na channels - slow conduction
<><><><>
Hypokalemia
◦ Usually increases risk of phase 4 depolarization and tachycardia
◦ But profound hypokalemia has been associated with AV block and severe bradycardia

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13
Q

Increased intracranial pressure - how can this lead to bradycardia?

A

◦ Cushing reflex
◦ Arterial pressure less than ICP → sympathetic stimulation heart → vasoconstriction, inotropy,
increased CO→ increased BP → baroreceptor response→ vagal stimulation → bradycardia

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14
Q

Key point:
◦ If heart rate or rhythm does not fit clinical picture, what should we do?

A

Then run an ECG
- LL gound, Ra-, La+

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15
Q

shock, types (6)

A

A critical state of hypoperfusion of tissues
◦ Tissue perfusion decreased to point insufficient to meet needs
<><><><>
Cardiogenic shock
◦ Pump failure: arrhythmia, heart disease
<><>
Hypovolemic shock
◦ Blood volume below critical level
<><>
Toxic shock
◦ Toxin causing failure of microvasculature, effects on heart, progressive
<><>
Endotoxic shock
◦ Bacterial toxin with effects on microvasculature
<><>
Septic shock
◦ Septicemia with effects on organs and vasculature
<><>
Neurogenic shock
◦ Severe bradycardia secondary to intense emotional stimuli, vagal stimulation or CNS trauma

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16
Q

most common type of heart failure we see in cattle

A

congestive, right sided

17
Q

Right-sided heart failure clinical signs

A

◦ Increased HR (tachycardia)
◦ Decreased: appetite, exercise tolerance and decreased production
◦ Venous engorgement (jugular vein distension)
◦ Ventral edema (limbs rarely or end stage)
◦ Ascites not easily detected (not large amount)
◦ Cool extremities
◦ If exercise intolerance is extreme: tachypnea, +/- dyspnea
◦ Animal stands with elbows abducted
◦ Arrhythmias may occur end stage, but are not common

18
Q

Left-sided heart failure
- prevalence
- clinical signs
- progression

A

◦ Rare in cows as lone left sided heart failure
<><>
◦ Tachycardia
◦ Exercise intolerance
◦ Weak pulse
◦ Weight loss > More obvious left-sided. Right-sided may be masked due to volume overload.
◦ Increased pulmonary pressures
<><><><>
◦ If slow, then right heart has time to compensate
◦ May see very little to no respiratory signs
◦ First signs of heart failure may be right heart failure
◦ If occur fast, acute pulmonary edema can develop > Dyspnea, frothing at mouth/nares

19
Q

Heart Failure
Clinical course

A

◦ Once clinical signs of heart failure start to develop most cases survive < a month
◦ With minimal stress may survive longer
◦ Complicated cases may last days > Acute left-sided, Congenital heart disease with secondary endocarditis

20
Q

Heart Failure
Treatment
prognosis

A

◦ Once clinical signs have developed
<><>
◦ Minimize stress
<><>
Supportive care:
◦ Diuretics, digoxin in valuable animals
◦ Underlying disease likely to cause permanent damage > even if could treat (eg. nutritional deficiency, endocarditis)
◦ Calving may improve signs if they worsened end lactation
◦ May only be buying time to salvage/slaughter
<><>
◦ Prognosis grave

21
Q

Disorders of Heart Rhythm
- what they indicate
- types we see, prevalence?

A

Most persistent arrhythmias in cattle indicate heart disease
<><>
Supraventricular dysrhythmias are rare
◦ Atrial fibrillation is the most common
<><>
Cattle do show sinus arrhythmia
◦ Some variation in rhythm is expected
◦ Correlation with respiratory cycle

22
Q

Atrial fibrillation
- what is it?
- cause?
- frequency, significance

A
  • Lack of coordinated atrial electrical activity
  • Caused by abnormal pulse conduction → resulting in unidirectional conduction block and random re-entrant activation of the atria
  • Some of these signals to hit AV node and conduct to ventricle → resulting in irregular ventricular rhythm
  • Infrequent > But always of clinically significance
23
Q

Atrial fibrillation
Risk factors, general

A

◦ Electrolytes and acid-base imbalance
◦ GI disease or peritoneal irritation
<><>
◦ Atrial enlargement (organic heart disease) > Not recommended to treat
◦ Atrioventricular valve regurgitation
◦ Ventricular failure
◦ Myocarditis
◦ Autonomic nervous system imbalance
◦ Anesthetic drugs and tranquilizers
◦ Unknown

24
Q

Atrial fibrillation
Risk factors for cattle in particular

A

◦ Gastrointestinal disease
◦ Foot rot and pneumonia
◦ Hypokalemia, hypocalcemia, and hypochloremia
◦ Metabolic alkalosis
◦ Experimentally: Metabolic alkalosis + hypokalemia
<><><><>
◦ Dx. more frequent in dairy than beef

25
Q

Atrial fibrillation
ECG diagnosis

A

Irregular cardiac rhythm
◦ Irregular R-R intervals
◦ QRS morphology normal but unpredictable rhythm
<><>
Absence of “P” waves on the ECG
◦ Irregular undulations “f” waves- fibrillation waves
◦ Appearance of these are variable- from almost nothing to fairly large
◦ Usually quite small in the bovine ECG (different from horses!)

26
Q

Atrial fibrillation
Treatment

A

◦ May resolve without treatment
◦ Managing underlying disease (electrolytes disturbances)
<><>
Treatment
◦ Quinidine gluconate or sulfate
◦ Careful management to avoid toxic effects of this drug
<><>
Treatment response not favorable.
◦ Persistence of AF in the bovine is associated with heart failure

27
Q

Valvular Heart Disease - types? what do we commonly observe?

A
  • Degenerative
  • Inflammatory
  • Infectious (viral / bacterial)
  • Trauma
    <><>
  • Most common manifestation of valvular disease is a murmur (s)
28
Q

Valvular Heart Disease
Risk Factors for vegetative endocarditis

A

◦ Foot abscess
◦ Rumenitis / Reticular abscess
◦ Predisposing factors would be those that disturb blood flow
> Valvular regurgitation, valve stenosis, congenital heart disease
> Disturbed blood flow damages the endocardium → adhesion of platelets and fibrin clumps → circulating bacteria can adhere
and colonize

29
Q

Valvular Heart Disease
- Endocarditis in cattle - types, most common causes

A

◦ Valvular or non-valvular
◦ In cattle most often bacteria
◦ Truperella pyogenes
◦ Alpha-hemolytic Streptococci
◦ Escherichia coli

30
Q

Endocarditis
Clinical findings
- signs, history
- treatment response
- murmur?
- valve?

A

◦ History of poor doing
◦ Weight loss
◦ Sometimes unusual forelimb stance
◦ Shifting lameness (treading)
◦ Fluctuating fever
◦ Malaise
◦ Fever responds to antibiotics but returns once antibiotics are withdrawn
<><><><>
- There may or may not be a murmur
- Any valve may be affected
- Right AV (tricuspid) valve is the most commonly affected
◦ Lesion tends to form on the atrial surface towards the valve margin

31
Q

Endocarditis
of the tricuspid valve sequelae / pathogenesis

A

Emboli to lungs
◦ Coughing
◦ Frequent showering → pulmonary hypertension
◦ Increases afterload, increasing right heart volume overload

32
Q

Endocarditis
of the mitral valve sequelae / pathogenesis

A

◦ Embolism to kidneys and myocardium
◦ Renal infarcts and myocardial infarcts
◦ Can cause septic arthritis, physitis
◦ Relatively rare in cattle

33
Q

endocarditis result

A
  • Ultimately may decompensate to heart failure
  • Some cases will respond to treatment
  • Scaring may cause permanent valve dysfunction or be set up for reinfection
34
Q

Endocarditis
Clinical pathology

A

◦ Neutrophilia: may be marked ( +/- left shift)
◦ Anemia
◦ Hyperfibrinogenemia
◦ Hyperglobulinemia (gamma-globulins) > Some cases normal (inactive)

35
Q

Endocarditis
Post-mortem

A

◦ Verrucous (wart-like), to vegetative lesions (resemble cauliflower)
◦ Many are valvular
◦ Valve may be distorted
◦ Examine chordae tendinae and rest of endocardium
◦ Culture negative most of the times
◦ Rest of lesions consistent with embolization, thrombi, abscesses

36
Q

Endocarditis
Treatment

A

◦ Ideal: Perform cultures before treating > Multiple cultures - 3 samples (1 every 8 hours)
◦ Broad-spectrum antibiotics
◦ If positive blood culture > Use antibiotic as per sensitivity panel
◦ Continue antibiotics for minimum 14 days
◦ Difficult to sterilize lesion > Poor penetration of antibiotics

3. Food Animal 3 (23 decks)

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