Page 1308 - Cote clinical veterinary advisor dogs and cats 4th

660 Mitral/Tricuspid Regurgitation Due to Myxomatous Valve Disease

generally increases with increasing disease (typically pulmonary edema and/or ascites) • Risk factors for CHF: valvular regurgitant
severity. (p. 408). status, left atrial and ventricular sizes (espe-
VetBooks.ir premature beats, atrial fibrillation, ventricular Chronic Treatment Dogs with CHF (acute or stabilized):
cially an increase in size over time), high
• ECG: tachyarrhythmia (e.g., supraventricular
blood concentrations of natriuretic peptides
• Chronic treatment with pimobendan prolongs
ectopy) usually indicative of severe disease,
presence of complication, or other cardiac
diseases the preclinical period in dogs with cardio- • Prognosis depends on age, left atrial and
ventricular sizes, severity of CHF, develop-
megaly but no signs of CHF (stage B2)
• Radiography: vertebral heart score (VHS) • Long-term treatment consists of optimal ment of complications, or presence of other
index can be used when assessing cardiac medical management of chronic CHF diseases (e.g., chronic kidney disease).
size (p. 1187). Pulmonary congestion and (p. 409). • Clinical trials indicate a mean survival time
edema indicate decompensated CHF. Other • Successful long-term management is based from onset of CHF of 8-10 months, but this
(noncardiac) causes for clinical signs of on titration and monitoring of medications may vary from days to years for different
respiratory disease should be excluded. that eliminate signs of CHF as completely dogs.
• CBC, serum biochemistry panel, urinalysis: as possible while causing as few adverse • Sudden death may occur but is uncommon,
usually unremarkable in less severe cases; cases consequences as possible. especially in the absence of preceding clinical
with CHF may have slightly increased levels • Open-heart surgical repair of myxomatous signs of CHF.
of liver enzymes and evidence of prerenal mitral valve disease in dogs has been
azotemia. described but is rarely performed. PEARLS & CONSIDERATIONS
• Echocardiography: atrial and ventricular size
increases with increasing disease severity. Drug Interactions Comments
Ventricular motion is usually exaggerated As described for CHF treatment (p. 409) • If presence of valvular regurgitation is
in advanced stages, whereas normal or equivocal by auscultation, the murmur or
reduced motion in the setting of severe Possible Complications regurgitant jet may become more obvious
regurgitation indicates myocardial failure. • Syncopal events after stressing the dog slightly (e.g., exercise).
Detection of thickened/ballooning AV valve, • Arrhythmia, most commonly atrial fibrilla- • CHF is unlikely in a dog diagnosed with
identification of regurgitant jet (with Doppler tion and ventricular ectopies MMVD with a respiratory sinus arrhythmia.
echocardiography) • Pulmonary hypertension • Murmur severity usually increases with
• Color Doppler echocardiography can • Rupture of first-order tendinous chord(s), increasing disease severity.
semiquantify regurgitant volume, which leading to a flail valve leaflet • Loud musical murmurs can occur but are
generally increases with increasing disease • Atrial tear, leading to acquired atrial septal unusual. The intensity of this type of murmur
severity. Spectral Doppler echocardiogram defect or pericardial effusion/cardiac is not usually related to disease severity.
can assess regurgitant velocity (generally tamponade • Mild pleural and/or pericardial effusion
≈5-6 m/s but may decrease in severe disease may develop from CHF. More pronounced
primarily due to high left atrial pressure). Recommended Monitoring accumulation of fluid in these locations raises
• Frequency of re-exams depends on severity the suspicion of other causes.
Advanced or Confirmatory Testing of valvular regurgitation and severity of CHF
• Serum natriuretic peptides: brain natriuretic (if present). Prevention
peptide (BNP) concentrations are often • Home monitoring of resting or sleeping • Because the liability for myxomatous AV
unremarkable in less severe cases. Moderate respiratory rates and body weight is recom- valve disease in dogs is inherited, the disease
to severe disease is usually associated with mended for dogs with moderate to severe prevalence among affected breeds should be
increased concentrations, most markedly in disease. reduced by breeding measures.
cases with CHF. However, increased BNP • Dogs without signs of CHF (stage B2) • Currently, no medication or management
concentration can also be seen in dogs with ○ Slight to moderate disease severity: q 6-12 is known to prevent the disease or slow
other heart diseases. months progression of valve changes, but onset of
• Blood culture in case of suspicion of vegeta- ○ Moderate to severe disease severity may signs of CHF are delayed by pimobendan
tive endocarditis require more frequent monitoring. treatment in dogs with preclinical disease
• Dogs with signs of CHF (stages C and D) and cardiomegaly (stage B2).
TREATMENT ○ After acute CHF has been successfully
treated, dogs can be treated at home. Technician Tips
Treatment Overview ○ Re-exam after 1-2 weeks of initiated • Teach owners to maintain resting or sleeping
• No treatment exists that slows or reverses therapy (check for signs of decompensated respiratory rate logs to monitor for develop-
the myxomatous valve lesions. CHF, dehydration, electrolyte imbalance, ment of acute decompensated CHF.
• Treatment is not indicated in mild disease renal dysfunction, and presence of any • Teach owners how to administer medications
(stage B1). other complication). Thereafter, q 3-6 and what signs should prompt a call or visit.
• Slow progression to clinical signs of CHF months; more severe cases may require
in dogs with cardiomegaly but no signs of more frequent monitoring. Client Education
CHF (stage B2). • Mild disease severity is suggestive of a long
• To alleviate clinical signs and improve quality PROGNOSIS & OUTCOME period without clinical signs; moderate to
of life and life expectancy in dogs with signs severe disease indicates a shorter period.
of CHF (stages C and D) by evacuating Dogs without signs of CHF (stage B): • Pimobendan treatment delays the onset
pulmonary edema/ascites and abolishing • Chronic disease progression: dogs with low- of clinical signs of CHF in dogs with
congestion, improving hemodynamic status, level disease severity may remain healthy for cardiomegaly.
and protecting from detrimental exposure to several years before signs of CHF develop. • If client is a breeder, inform about genetics
neurohormones • Pimobendan treatment prolongs the preclini- of the disease and impact on future breeding.
cal period in dogs with cardiomegaly but no • Discuss appropriate level of exercise (e.g.,
Acute General Treatment signs of CHF (stage B2). no restrictions for low disease severity, avoid
Acute CHF treatment is indicated when • Risk factors for progression: severity of valve strenuous exercise in moderate to severe
overt signs are caused by fluid retention lesions, age, and sex cases).

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