6) Myxomatous valve diseases in dogs

Question 1

General information

Answer 1

the most common cardiac disease in dogs

also called mitral valve disease

Question 2

Prevelance of Myxamatous mitral valve disease

Answer 2

– Around 3,5%
– Increase with age
– Small breed dogs
– Males > females
– May reach 70-90% in
certain breeds above 8-10
yrs
– MV > MV/TV > >TV

Question 3

Pathomechanism of MMVD

Answer 3

Activation and transformation of mitral valve valvular interstitial cells into an active phenotype leading to
remodeling of the extracellular matrix and compromise of the structural components of the mitral valve
leaflets
• TGF-beta appears to be the dominant signaling pathway controlling MMVD pathogenesis
• MMVD in dogs associated with high serum serotonin, increased expression of serotonin-receptors, autocrine
production of serotonin within the mitral valve leaflets, and downregulation of serotonin clearance
mechanisms
• Serotonin and TGF-beta pathways are both able to activate mitral valve valvular interstitial cells

Expansion of extracellular matrix with
glycosaminoglycans and
proteoglycans
• Valvular interstitial cell alteration; and
attenuation or loss of the collagenladen
fibrosa layer
• These lead to malformation of the
mitral apparatus, biomechanical
dysfunction, and mitral
incompetence.

Question 4

Signs

Answer 4

Thickening of the valve leaflets,
distorted edges of the leaflets,
„knoting” = myxomatous
degeneration
• Thickened and/or ruptured chordae
tendineae
• Dilated mitral ring (annulus)

the walves will not close properly, there may be some mitral
valve prolapse -they close backwards
insufficiency causes active volume overload - extrecentric hypertrophic
mitral valve dilation -> insuffiency -> more blood going back during systole
dilation of volume

• Mitral valva prolapse as a consequence

dilation of the left atrium
-> pressure transmits to pulmonary veins - increases capillary pressure in lungs -> pulmonary edema in acute cases
in chronic disease: pulmonary hypertension will develop - respiratory distress

Question 5

Diagnosis of MVDD

Answer 5

Physical examination
• Systolic heart murmur (left apical)
• Sign of left sided heart failure
• +/- Signs of right sided heart failure

Diagnostic imaging
Radiography: cardiac chamber enlargement, lung edema
Echocardiography (diagnostic)

you need to check the side of the heart!
color doppler or spectral doppler
check if there is hypertrophy

Question 6

ACVIM consensus statement - guide about MMVD

Answer 6

A : patients at high risk but no identifiable structural
disorder of the heart
B1 : asymptomatic patients no evidence of cardiac
remodeling
B2: asymptomatic patients with cardiac remodeling
C: Past or current clinical signs of heart failure associated
with structural heart disease.
D: Patients with end-stage disease with clinical signs of
heart failure refractory to „standard” therapy.

Question 7

Treatment of asymptomatic MVDD in stage B1 or B2

Answer 7

Pimobendan is the only treatment, studies showed that all the others are ineffective -> only in stage B2!!!!!!

Question 8

Treatment of MMVD C and D

Answer 8

• Furosemide/torsemide
• Pimobendan
• Spironolactone (ACE-I) - but this didnt effect the survival of the animal

Question 9

complications of treatment of MMVD stage C and D

Answer 9

pulmonary hypertension
arrythmias
tearing of the left atrium

Question 10

Never mix MMVD with?

Answer 10

Endocarditis, has different clinical signs:
• Rare, often large breeds
• Bacterial infection (bacteriaemia)
– Staphylococcus spp, Streptococcus spp, Escherichia coli, and
Bartonella spp.
• Aorta stenosis (congenital heart diseases) are predisposing factors
• Congestive heart failure, immune-mediated disease, and
thromboembolism are the major complications
• Thrombus/embolus formation/infarcts
Clinical signs:
• Fever
• Reluctance to move (back pain, polyarthritis), and intermittent lameness
(muscle embolization, polyarthritis)
• Heart failure
• Rarely syncope, weakness due to AV-block

Diagnosis:
• Sudden appearance of a murmur
• Fever, elevated WBC, CRP
• Thickening of the valves, large vegetations
– aortic valve/mitral valve
• Hemoculture
• PCR
Treatment :
• iv. broad spectrum antibiotics, later per os
• treating heart failure if needed
• Antithrombotic treatment (clopidogrel, heparin, aspirin)