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Y4 SA - Cardio-Respiratory > Valvular Heart Diseases > Flashcards

Valvular Heart Diseases Flashcards

1
Q

Name the most common cardiac disease in dogs

A

Myxomatous degenerative valve disease

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2
Q

Describe the pathogenesis of myxomatous degenerative valve disease

A

Idiopathic
Slow progression over several years
Risk of sudden death low
Small breeds
Mitral valve and tricuspid valve most commonly affected

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3
Q

What changes occur in the heart is myxomatous valvular degeneration?

A
  • Nodular thickening of the valve leaflets: proteoglycan accumulation
  • Lengthened or ruptured chordae
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4
Q

Describe the aetiology and predispositions for myxomatous degenerative valve disease

A

Idiopathic condition – multiple hypotheses:
- Abnormalities in collagen and extracellular matrix formation
- Abnormalities of serotonin signalling
- Mechanical stress
Predisposition in Cavalier King Charles Spaniel
Middle aged/older dogs

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5
Q

How does the gross pathology of the heart change in myxomatous degenerative valve disease?

A
  • LA and LV dilatation: eccentric hypertrophy due to chronic volume overload
  • Elongation chordae tendinae
  • Thickened, deformed leaflets
  • Jet lesions: damage to the left atrial wall
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6
Q

Describe the microscopic changes in the heart if myxomatous degenerative valve disease

A

Accumulation of glycosaminoglycans (pink sedimentary material) within the valve leaflets and a disrupted collagen matrix

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7
Q

If there are valve leaks, what happens next?

A
  • Leakage of blood back into atria (left most likely)
  • Reduction in forward stroke volume = blood leaving the heart in each pump cycle
  • If there is a leaky valve some blood goes back into the atrium when it should normally all go out of the ventricles through the aorta
  • Increase in volume of blood entering left ventricle in next diastole = volume overload
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8
Q

What commonly occurs secondary to chronically elevated left atrial pressure and can be seen secondary to concurrent respiratory/lung pathology as seen in small breeds?

A

Pulmonary hypertension

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9
Q

Define afterload

A

The work of the heart to pump blood

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10
Q

Define preload

A

The volume of the left ventricle at the end of diastole

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11
Q

A volume overload due to a constant increased preload causes?

A

Eccentric hypertrophy

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12
Q

How do valve leaks affect preload and afterload?

A
  • Decreased afterload as there is less blood to pump out of the heart as it goes back into the atria (which is easier than out of the aorta)
  • Increased preload as the volume in the LV at the end of diastole is increased
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13
Q

How do valve leaks affect cardiac output?

A

Reduced cardiac output as there is a decreased stroke volume

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14
Q

What are the consequences of decreased cardiac output?

A

Activation of sympathetic NS -> increased HR and contractility
Activation of RAAS

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15
Q

What are the consequences of RAAS activation?

A

Retention of Na and fluid
Vasoconstriction to increase afterload
Increased circulating volume to increase preload

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16
Q

What are the consequences of increased afterload and preload?

A

Chamber dilation
-> Mitral regurgitation

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17
Q

Describe the different stages of myxomatous degenerative valvular disease

A

A = at risk
B1 = murmur and no enlargement
B2 = murmur and enlargement
C1 = CHF, hospitalised
C2 = CHF, at home
D1 = refractory, hospitalised
D2 = refractory, at home

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18
Q

How might a dog with myxomatous degenerative valve disease present in the consult room/on clinical exam

A
  • Small breeds predisposed
  • Adult/older dogs
  • Loud harsh heart murmur, left apical systolic
  • Dyspnoea, tachypnoea, crackles
  • Exercise intolerance
  • Cough
  • Possibly no clinical signs
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19
Q

Once the clinical exam has been performed on a dog with suspected MDVD, what are the next steps?

A
  • Thorough auscultation to locate and describe the murmur: this will give you your diagnosis!!
  • Blood pressure
  • Clinical pathology: Biomarkers (NTProBNP)
  • Radiography
  • ECG
  • Echocardiography
  • Ambulatory ECG
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20
Q

List the clinical signs of right sided CHF

A

Ascites
Hepatomegaly
Jugular pulsation

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21
Q

How can blood pressure be used to investigate myxomatous degenerative valvular disease?

A
  • Often normal
  • Hypertension → increased afterload → worse regurgitant fraction = BAD!
  • More blood is pushed back into the atrium
  • Hypotension if forward (systolic) failure
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22
Q

How can blood tests and biomarkers be used to investigate myxomatous degenerative valvular disease?

A
  • Prerenal azotaemia, particularly on diuretics
  • Assess electrolytes, particularly on diuretics
  • Biomarkers:
    NT-proBNP - helpful to differentiate respiratory/cardiac cause of cough. Marker for HF.
    Troponin I - marker for myocardial cell damage
23
Q

How can thoracic radiographs be used to investigate myxomatous degenerative valvular disease?

A
  • DV + right lateral
  • Cardiac size: Tracheal elevation, Bulges?
  • Pulmonary vessels
  • Lung infiltrate
  • Effusions?
24
Q

What are some common arrythmias seen with myxomatous degenerative valve disease?

A
  • Prolonged P wave = left atrial enlargement
  • Tall R wave = left ventricular enlargement
    In advanced cases:
  • Supraventricular premature complexes
  • Atrial fibrillation
  • Ventricular premature complexes
25
Q

If a patient with suspected myxomatous degenerative valve disease has sinus arrhythmia, what does this mean?

A

NOT in congestive heart failure - preclinical disease

26
Q

What is the best diagnostic method to confirm suspicions of MDVD?

A

Echocardiography

27
Q

What is echocardiography used for in MDVD?

A

To assess severity, progression of disease and response to treatment

28
Q

How will a heart with MDVD appear on echocardiography?

A
  • Thickened atrioventricular leaflets, may see prolapse
  • Presence of MR on colour Doppler – size of jet depends on severity
  • LA enlargement: LA/Ao ratio, LA major
  • LV enlargement: Eccentric hypertrophy with rounded LV – especially increased internal diameter in diastole (LVIDd, from increased preload)
  • Hyperdynamic systolic function
  • Tricuspid regurgitation
  • Pulmonary hypertension
29
Q

How does the left side of the heart normally appear on echo?

A

Bullet shaped left ventricle, square shaped left atrium

30
Q

How should the size of the left atrium compare to the size of the aorta in a normal animal?

A

The atrium should be no more than 1.5x the size of the aorta

31
Q

What is a holter/ambulatory ECG?

A

24h ECG
Quantification of arrhythmias
Atrial fibrillation: response to treatment

32
Q

Describe the treatment of myxomatous degenerative valve disease based on the stage

A

A – none indicated, monitor at routine appointments
B1 – none indicated, murmur will be present, HAMLET APP
B2 – PIMOBENDAN, HAMLET APP
C – CHF therapy as standard
D – as for C with increasing doses and additional therapies e.g. sequential nephron blockade

33
Q

Name the 4 drugs used in the therapy of CHF - in the correct order

A

Furosemide
Pimobendan
ACEi
Spironolactone

34
Q

Why is Pimobendan given in the B2 stage of MDVD?

A

Delays the onset of heart failure

35
Q

Name two drugs given to patients with supraventricular arrythmias

A

Diltiazem
Digoxin

36
Q

Name 1 drug given to patients with ventricular arrythmias

A

Solatol - do not use if heart failure is confirmed or suspected

37
Q

Name a drug given to patients with pulmonary hypertension

A

Sildenafil

38
Q

When should cough suppressants be used?

A

Should only use if it is a genuine heart failure cough as an animal is usually coughing for a reason

39
Q

Describe the prognosis of MDVD

A
  • Very variable - Some asymptomatic dogs never develop CHF
  • Breed? CKCS better prognosis (earlier onset)
  • Once signs of CHF appear prognosis worse but timeline variable
  • Large breed dogs can show myocardial failure and deteriorate more rapidly
40
Q

What is endocarditis?

A

Very rare!
Infection of 1 or more endocardial surfaces (valves/leaflets)

41
Q

Which valves are most affected by endocarditis?

A

Aortic or mitral

42
Q

List some possible agents that can cause bacterial endocarditis

A

Streptococcus spp
Staphylococcus spp
E. Coli
Pseudomonas

43
Q

Describe the aetiology of bacterial endocarditis

A
  • Transient, persistent bacteraemia → occult infection (GI, dental, oropharynx), IV catheter, recent surgery
  • Damaged valvular endothelium: high velocities, turbulent blood flow
  • Bacteria ability to adhere through various mechanisms
  • Hypercoagulable states
44
Q

Describe the pathology of bacterial endocarditis

A
  • Vegetations on the endocardial surface of the valve leaflets: small nodules to polypoid
  • Affected valves usually deformed, can be perforated, haemorrhagic
  • Septic/sterile arterial embolisation (kidney, heart, lung, brain)
45
Q

Describe the microscopic pathological findings in bacterial endocarditis

A

Platelets, RBC, WBC, bacteria, fibrin
Fibrous tissue, calcification
Bacteria within vegetation

46
Q

List the diagnostic methods for bacterial endocarditis

A
  • Blood culture
  • Echocardiography
  • ECG
  • Clinical pathology
47
Q

Describe blood culture as a diagnostic method for bacterial endocarditis

A
  • Prior to antibiosis, ideally if pyrexia present
  • Aseptic technique
  • 3 samples from different puncture sites, 10 mL per sample (total of 20-30mL increase the chance of positive result)
  • Frequently negative
  • False +ve due to skin contamination
48
Q

Describe echocardiography as a diagnostic method for bacterial endocarditis

A
  • Valvular vegetations
  • Size -> risk of embolisation
  • Regurgitation = MURMUR!
  • Systolic dysfunction
49
Q

Which criteria is used for diagnosis of bacterial endocarditis?

A

Modified Dukes criteria

50
Q

Describe how the modified Dukes criteria is used to diagnosed bacterial endocarditis

A

Based on major and minor clinical signs
Definitive =
- 2 major OR
- 5 minor OR
- 1 major + 3 minor

51
Q

List the major criteria in the modified Dukes criteria

A
  • Positive echocardiogram
  • New valvular insufficency
  • Positive blood culture
52
Q

List the minor criteria in the modified Dukes criteria

A
  • Fever
  • Medium/large breed
  • Subaortic stenosis
  • Thromboembolic disease
  • Immune mediated disease
  • Positive blood culture not meeting major criteria
53
Q

How is bacterial endocarditis treated?

A

Bactericidal antibiotics – ideally based on culture and sensitivity: Fluoroquinolone + potentiated amoxicillin + metronidazole whilst awaiting culture
- Intravenously for at least 7 days
- Minimum course of 6 weeks, might need much longer course

54
Q

Describe the prognosis of bacterial endocarditis

A
  • Guarded
  • Recurrence and complications possible
  • Long term valvular damage

Y4 SA - Cardio-Respiratory (10 decks)

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