Endocardiosis
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a.k.a. myxomatous mitral valve disease, mitral insufficiency, mitral regurgitation, chronic valvular disease
- Common lesion in heart valve (dog)
- Most often in the mitral valve
- Rare in cats
Signalment
- Age: Middle Age to Old dogs
- Sex: Males
- Genetics & Predisposed Breeds: Most common in smaller breeds (Chihuahua, Boston Terrier, Poodle, Pomeranian); Large Breeds (German Shepherd, Collies)
Description
Valvular insufficiency due to thickening and shortening of the valve leaflets. Consequently, during systole a small stream of blood passes back into the left atrium causing a white jet lesion where the blood contacts the atrial wall and atrial dilation. Advanced cases progress to left sided (congestive) heart failure and then to concurrent right sided heart failure.
Diagnosis
Clinical Signs
Signs depend on stage of disease:
-Coughing
-Syncope
-Weight loss
-Pale or cyanotic mucus membranes
-Prolonged capillary refill time
-Left-sided heart failure signs:
- exercise intolerance
- weakness
- dyspnoea
- inappetance
- lethargy
-Right-sided heart failure signs:
- hepatomegaly
- jugular pulses & distension
- pleural effusion
- ascites
- peripheral edema
Physical Exam
-Incidental finding: systolic click heard in asymptomatic animals
-Murmur over the left heart apex
-Snaps, crackles, pops heard if pulmonary edema is present
-Muffled heart sounds in the presence of pleural/pericardial fluid
Radiography
-Left sided heart enlargement
-(+/-) Left atrial enlargement (DV view appears at 2-3 o'clock position)
-(+/-) Left ventricular enlargement
-(+/-) Dorsal displacement of trachea
-(+/-) Bronchial compression
-Pulmonary venous congestion and/or edema
-(+/-) Right-sided signs (distended caudal vena cava, ascites, pleural effusion, heptaomegaly)
Electrocardiography (ECG)
-Left atrial enlargement pattern
-Left ventricular enlargement pattern
-Rhythm disturbances (supraventricular arrhythmias: atrial premature complexes, atrial tachycardia, and ventricular rhythm disturbances)
Echocardiography
-Irregularities of the valves affected (e.g. thickening, shortening, and/or prolapse of the valve leaflets)
-Abnormal valve movements & valve regurgitation
-Left atrial enlargement (wide P wave)
-Left ventricular dilation (tall R wave, wide QRS complex)
Early Stage of disease
- Normal to increased fractional shortening of the myocardium
Later Stage of disease
- Decreased fractional shortening of the myocardium
Treatment
- Left-sided heart failure treatment given at the onset of clinical signs.
- Right-sided heart failure treatment given at the onset of clinical signs.
- Symptomatic treatments are also given if clinical signs persist while the animal is on heart failure medications.
Complications
- Arrhythmias
- Bronchial Compression
- Ruptured Chordae Tendineae
- Atrial Rupture
Prognosis
-Asymptomatic patients may live for many years.
-Some patients remain stable for years on heart failure medications