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658 Mitral/Tricuspid Regurgitation Due to Myxomatous Valve Disease

TREATMENT cardiopulmonary bypass; postoperative PROGNOSIS & OUTCOME
management complications are common. • Long-term prognosis depends on the severity
Treatment Overview
VetBooks.ir Treatment focuses on initial control of CHF results in canine patients; possible damage • Surgical approach and new interventional
○ Balloon valvuloplasty (MVS): inconsistent
of the dysplasia: guarded in severe cases
signs, with therapy to reduce venous congestion
to the mitral valve apparatus with worsen-
ing of mitral regurgitation
(diuretics), improve function (inodilators),
inhibit sodium/water retention, counteract vaso- ○ Hybrid procedure (MVS): closed com- procedures may offer a better outcome in
the future.
constriction (angiotensin-converting enzyme missurotomy with balloon valvuloplasty
[ACE] inhibitors, vasodilators), and control PEARLS & CONSIDERATIONS
supraventricular arrhythmias (digoxin, calcium Behavior/Exercise
channel or beta-blockers). Consider referral Restrict exercise and excitement in patients with Comments
to cardiologist for diagnosis and advice on collapsing or syncopal episodes. A disproportionate number of cases occurs in
treatment plan. the bull terrier breed.
Drug Interactions
Acute General Treatment • Excessive use of diuretics is contraindicated Prevention
• Management of CHF (p. 408) due to the decrease in preload, electrolyte Do not breed affected animals.
• Digoxin, calcium channel blocker, or beta- disturbances, prerenal/renal azotemia, and
blocker: management of supraventricular increased risk of digitalis toxicity. Technician Tips
arrhythmias (pp. 94 and 96) • ACE inhibitors may reduce glomerular filtra- These patients are at risk for pulmonary edema
• For myocardial failure (advanced/end-stage tion rate and cause azotemia; hypotension and CHF. Teaching the owner to keep a log
state characterized by left ventricular may occur when used with diuretics; risk of of the patient’s resting or sleeping breathing
+
hypocontractility): inodilators (pimobendan hyperkalemia when K is supplemented or rate to monitor for changes can be an effective
+
0.2-0.3 mg/kg PO q 12h) K -sparing diuretics are used concurrently. way to monitor progression of disease.
Chronic Treatment Possible Complications Client Education
• Medical therapy • Recurrence of signs due to progression of • Monitor respiratory rate at rest, exercise
○ Diuretics, ACE inhibitors, inodilators, CHF tolerance, and appetite.
and antiarrhythmics after acute treatment • Systemic thromboembolism (cats) • Advise client not to breed affected animals.
(p. 409) • Left atrial rupture (dogs)
○ In cats, antiplatelet and/or anticoagulant • Postsurgical coagulation disturbances possible SUGGESTED READING
therapy for prevention of atrial thrombus after mitral valve replacement, restenosis Kittleson MD, et al: Congenital abnormalities of
formation (p. 74): clopidogrel, aspirin, (MVS) the atrioventricular valves. In Kittleson MD, et
warfarin, unfractionated heparin/low- al, editors: Small animal cardiovascular medicine,
molecular-weight heparins Recommended Monitoring New York, 1998, Mosby, pp 273-281.
○ Address PH, if present (p. 838). Recheck exams should include thoracic AUTHOR: João S. Orvalho, DVM, DACVIM
• Surgical therapy radiographs, serum renal panel (including EDITOR: Meg M. Sleeper, VMD, DACVIM
○ Mitral valve replacement or open mitral electrolytes), systolic blood pressure measure-
commissurotomy (MVS): requires ment, digoxin levels (if applicable), and ECG.

Mitral/Tricuspid Regurgitation Due to Myxomatous Valve Disease Client Education
Sheet

BASIC INFORMATION degenerative mitral valve disease (DMVD), breeds such as Cavalier King Charles spaniels,
mitral valve disease (MVD), endocardiosis papillons, miniature poodles, Yorkshire terriers,
Definition Chihuahuas, and dachshunds.
Myxomatous degeneration is a pathologic dis- Epidemiology
turbance in the organization of the connective SPECIES, AGE, SEX ASSOCIATED DISORDERS
tissue of the atrioventricular (AV) heart valves. MMVD is the most common cardiac disease Myxomatous degeneration of the semilunar
The disease most frequently includes the mitral in dogs. The prevalence increases with age. The valves (very uncommon in dogs and, when
valve, with or without changes of the tricuspid disease is uncommon in young individuals but present, seldom of clinical importance),
valve, and the disease is commonly referred to common in old dogs. Males develop the disease pulmonary hypertension, CHF, and various
as myxomatous mitral valve disease (MMVD). at a younger age than females. cardiac arrhythmias
Insufficient coaptation of the leaflets leads to AV Clinical Presentation
valve regurgitation, particularly mitral regurgita- GENETICS, BREED PREDISPOSITION
tion (MR), and subsequently, chronic volume The age at which the disease develops is most DISEASE FORMS/SUBTYPES
overload with atrial and ventricular dilation. likely inherited as a polygenetic threshold trait American College of Veterinary Internal
Eventually, the heart might become incapable (i.e., multiple genes influence the trait, and Medicine (ACVIM) Consensus Statement
of meeting the increased workload imposed on a certain threshold has to be reached before recommends staging into four classes (A to D):
it, and congestive heart failure (CHF) develops. the disease develops). Males have a lower • Class A: dogs at risk for developing heart
threshold than females, leading to a higher disease but that have no identifiable
Synonyms disease prevalence at a given age. Although structural disorder of the heart (e.g.,
Chronic valvular disease (CVD), chronic mitral encountered in all breeds, the highest disease Cavalier King Charles spaniels without heart
valve disease, degenerative valvular disease, prevalence is seen among small to medium-sized murmurs)

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