myxomatous mitral valve disease of the dog Flashcards
what is the epidemiology and prevalence
- 75-80% of canine cardiac diseases
- small breed dogs»_space; large breed dogs
- no sex predilection M=F
- synonyms: degenerative mitral valve disease, mitral valve disease, endocarditis
what is the etiology
unknown
- collagen abnormality (collapsing trachea, IVDD, luxating patellas, cruciate ligament rupture)
- hereditay
- no proven infectious etiology
what is the timing of MMVD murmer
systolic
location of MMVD murmur
- left > right
- apical > basilar
intensity of MMVD
- soft
- moderate
- loud
- thrilling
what is a mitral murmur
- specific and sensitive for presence of disease
- variable as an indicator of severity of disease
what are false positives with MMVD murmur
- common
- loud murmur, but mild disease
what are false negatives with MMVD murmur
- uncommon
- soft murmur, but severe disease
what are the key characteristics in assessing severity of MMVD
left atrial and ventricular size
how to directly asses LA and LV size
- thoracic radiography
- echocardiography
how to indirectly assess LA and LV size
less reliable
- murmur intensity
- ECG
- BNP concentration
what do you see in an xray with MMVD
- LA, LV enlargement
- pulmonary venous distention
- perihilar interstitial/alveolar
what do you see in an echo with MMVD
- thickened valve leaflets
- prolapse of leaflets into LA
- ruptured chordae tendineae
- color flow doppler reveals regurgitant flow into LA
what are the MVD stages/classification system
- stage A: no disease, at risk (older small breed dog)
- stage B: MVD present, no current or historical clinical signs (asymptomatic, pre-clinical)
- stage B1: no cardiac enlargement
- stage B2: cardiac enlargement present
- stage C: MVD present, current or historical heart failure, conventional CHF
- stage D: MVD present, advanced disease, refractory clinical signs
why stage asymptomatic (stage B) MVD?
- many dogs with mild MVD (B1) will never develop CHF (no reason to tx)
- dogs with secondary cardiac enlargement (B2) have greater risk for future CHF, which is reduced by oral pimobendan
dyspnea in the dog: differential diagnosis (2)
- CHF due to MMVD (stage C) - loud murmur, substantial LH enlargement, high BNP conc
- primary respiratory disease (pulmonary fibrosis, pneumonia, collapsing trachae) - no or soft murmur, no LH enlargement, normal BNP conc.
dogs can have both
what is the acute CHF therapy for MVD
- Furosemide (preload)
- Oxygen
- Nitroprusside (pre/afterload)
- Dobutamine (inotropy)
in less critical cases N & D - pimobendan (FOP)
what is the chronic CHF therapy for MVD
- Furosemide (preload)
- Ace inhibitors (dec. RAAS)
- Pimobendan
- Spironolactone
what are MVD complications
- LA tears
- ruptured chordae tendinae
- arrhythmias
what are LA tears due to MVD complications
- acute pericardial effusion and cardiac tamponade
- low output heart failure - death
what is ruptured chordae tendinae due to MVD complications
- acute worsening of regurgitation volume
- acute, fulminant CHF
what are arrhythmias due to MVD complications
- atrial fibrillation
- atrial and ventricular premature beats
what is the effect of atrial fibrillation
loss of atrial contraction can increase left atrial and venticular pressures sufficient to cause new onset CHF
what is valvular endocarditis
- inflammation of the valve tissue usually due to an infectious agent, usually bacterial
- dogs, cats, horses, pigs (mitral and aortic valves)
- ruminants (tricuspid and pulmonic valves)
what is the gold standard diagnosis for valvular endocarditis
post-mortem isolation of bacteria from affected valve
what are the major criteria for antemortem diagnosis
- suspicious valve lesions detected by ultrasound
- positive blood cultures
- recent onset of diastolic heart murmur due to aortic valve insifficiency
treatment for valvular endocarditis
- long-term antibiotic therapy
- preferably guided by blood culture results
what is the prognosis for valvular endocarditis
very guarded
