Degenerative Mitral Valve Disease

Mitral dyplasia. Courtesy of A. Jefferies

Also known as MVD

• Common in dogs and cats

• Rare in other species

Signalment

Genetics & Predisposed Breeds: Large Breeds (e.g., Bull Terrier, Miniature Bull Terrier, English Bulldog, Great Dane, German Shepherd, Newfoundland, Irish Setter)

Description

• Congenital malformation of the mitral valve and its supporting structures (chordae tendineae, papillary muscles, valvular leaflets, annulus) results in mitral stenosis (narrowing) or regurgitation (insufficiency)

• Mitral Stenosis: left ventricle is not able to fill completely during diastole; Increase in left atrial pressures

• Mitral Regurgitation (Insufficiency): leaky mitral valve allows blood to flow back into atria causing increased left atrial pressure and increased pressure in the pulmonary veins

Diagnosis

History & Clinical Signs

Mild defects may be asymptomatic

Signs of left sided congestive (dilated) heart failure:

-Cough

-Tachypnea/Dyspnea

-Exercise Intolerance

-Syncope

-Pale Mucous Membranes

-Tachycardia

-Arrhythmias

Physical Exam

-Left apical systolic murmur

-Left diastolic murmur

-Poor pulses

Radiographic Findings

-Left atrial enlargement

-Left ventricular enlargement

-Enlargement of pulmonary veins

-Pulmonary edema

Echocardiographic Findings

-Left atrial enlargement

-Left ventricular enlargement

-Malformed valve leaflets

Doppler can detect mitral stenosis or regurgitation and estimate pressures in the left atrium and pulmonary veins

Electrocardiographic (ECG)

-May be normal

-Signs of left atrial (wide P waves)

-Signs of left ventricular (tall R waves)

-Signs of arrhythmias

Treatment

Control left atrial pressure and manage left sided congestive heart failure

Goal of treatment for congestive heart failure:

-Diuretics (decrease venous congestion)

-ACE-inhibitors; Vasodilators (inhibit water retention and dilate the vessels)

-Anti-coagulants (cats) to prevent thrombus formation

Prognosis

Mild Defects

-Excellent

Severe Defects

-Guarded

From Pathology

Often associated with mitral regurgitation and left atrial volume overload. Usually progresses to left sided heart failure.

Incidence:

Mitral dyplasia. Courtesy of A. Jefferies

• Most common congenital defect in cats.
• Also reported in pure breed dogs E.g GSD, Great Danes.

Clinical Signs:

• Often murmur is the only clinical sign; pansystolic with increased intensity over the mitral valve area.
• May also see exercise intolerance, dyspnoea and coughing.

Diagnosis:

• Left atrial enlargement on radiology and ECG.
• Doppler echocardiography can dtect abnormal flow.

Treatment:

• Prognosis poor, medically manage left heart failure with ACE-inhibitors etc.