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Also known as: '''''MVD — Mitral Valve Disease — Mitral insufficiency — Mitral endocardiosis — Myxomatous Mitral Valve Disease (MMVD) - Endocardiosis'''''

Also known as: '''''MVD — Mitral Valve Disease — Mitral insufficiency — Mitral endocardiosis — Myxomatous Mitral Valve Disease (MMVD) - Endocardiosis'''''

==Introduction==

==Introduction==

[[Image:AV valve dysplasia cat.jpg|right|thumb|200px|<small><center>'''Mitral dyplasia'''. Courtesy of A. Jefferies</center></small>]]

[[Image:AV valve dysplasia cat.jpg|right|thumb|200px|<small><center>'''Mitral dyplasia'''. Courtesy of A. Jefferies</center></small>]]

Mitral valve dysplasia is a congenital malformation or degeneration of the mitral valve leaflets and its supporting structures (chordae tendinae, papillary muscles, valvular leaflets, annulus) resulting in valvular regurgitation (insufficiency). It is common in dogs and cats and rare in other species.

Mitral valve dysplasia is a congenital malformation or degeneration of the mitral valve leaflets and its supporting structures (''chordae tendinae'', papillary muscles, valvular leaflets, annulus) resulting in valvular regurgitation (insufficiency). It is common in dogs and cats and rare in other species.

Chronic mitral regurgitation leads to volume overload of the left heart, which results in dilatation (eccentric hypertrophy) of the left ventricle and atrium. When mitral regurgitation is severe, cardiac output decreases, which results in signs of left sided cardiac failure (LCHF) and pulmonary venous congestion. Dilatation of the left-sided chambers predisposes affected animals to [[:Category:Arrhythmia|arrhythmias]]. In some cases, malformation of the mitral valve complex causes a degree of valvular stenosis as well as insufficiency.

Chronic mitral regurgitation leads to volume overload of the left heart, which results in dilatation (eccentric hypertrophy) of the left ventricle and atrium. When mitral regurgitation is severe, cardiac output decreases, which results in signs of left sided cardiac failure (LCHF) and pulmonary venous congestion. Dilatation of the left-sided chambers predisposes affected animals to [[:Category:Arrhythmia|arrhythmias]]. In some cases, malformation of the mitral valve complex causes a degree of valvular stenosis as well as insufficiency.

==Diagnosis==

==Diagnosis==

===History===

===History===

Animals may remain asymtomatic for years. Typical reported signs include exercise intolerance and dyspnoea as a result of reduced cardiac output and a ventilation perfusion mismatch due to pulmonary oedema. A progressive cough often during rest or recumbancy is frequently seen and needs to be distinguished from primary respiratory disease. Sudden death is possible due to a left atrial tear or advanced pulmonary oedema.  

Animals may remain asymptomatic for years. Typical reported signs include exercise intolerance and dyspnoea as a result of reduced cardiac output and a ventilation perfusion mismatch due to pulmonary oedema. A progressive cough often during rest or recumbency is frequently seen and needs to be distinguished from primary respiratory disease. Sudden death is possible due to a left atrial tear or advanced pulmonary oedema.  

===Clinical Signs===

===Clinical Signs===

* Left apical systollic murmur

* Left apical systolic murmur

* Left sided congestive heart failure

* Left sided congestive heart failure

**Resting Tacchycardia

**Resting Tachycardia

**Pale Mucous membranes

**Pale Mucous membranes

** Prolonged Capillary refill time (CRT)

** Prolonged Capillary refill time (CRT)

** Loss of sinus arrhythmia

** Loss of sinus arrhythmia

** Cardiac arrhythmias e.g. Atrial fibrillation, Atrial premature complexes

** Cardiac arrhythmias e.g. Atrial fibrillation, Atrial premature complexes

===Diagnostic imaging===

===Diagnostic imaging===

====Radiography====

====Radiography====

Left Lateral, right lateral and ventrodorsal views of the thorax are needed. The key radiographic signs associated with mitral valve dysplasia and resulting left sided congestive heart failure are cardiomegaly, pulmonary venous congestion (enlarged pulmonary arteries and veins) and pulomary oedema. Cardiomegaly may lead to dorsal displacement of the trachea.  

Left Lateral, right lateral and ventrodorsal views of the thorax are needed. The key radiographic signs associated with mitral valve dysplasia and resulting left sided congestive heart failure are cardiomegaly, pulmonary venous congestion (enlarged pulmonary arteries and veins) and pulmonary oedema. Cardiomegaly may lead to dorsal displacement of the trachea.  

Evidence of Right sided congestive heart failure maybe evident in severe cases e.g. distended caudal vena cava, hepatomegaly, ascites, pleural effusions.

Evidence of Right sided congestive heart failure maybe evident in severe cases e.g. distended caudal vena cava, hepatomegaly, ascites, pleural effusions.

====Echocardiography====

====Echocardiography====

Evidence of left atrial and left venrticular enlargement is visible on echocardiography. The 'fractional shortening' is also increased which is measured as the percentage change in the left ventricular diameter during systole and is used as a measure of systollic function. It is also possible to see structural changes in the valve leaflets in some cases. The regurgitant jet of blood can be detected using colour doppler and evidence of turbulent flow.

Evidence of left atrial and left ventricular enlargement is visible on echocardiography. The 'fractional shortening' is also increased which is measured as the percentage change in the left ventricular diameter during systole and is used as a measure of systolic function. It is also possible to see structural changes in the valve leaflets in some cases. The regurgitant jet of blood can be detected using colour doppler and evidence of turbulent flow.

===Electrocardiogram (ECG)===

===Electrocardiogram (ECG)===

A resting ECG trace may show evidence of an enlarge left atrium (Wide P Wave), an enlarged left ventricle (Tall R wave, wide QRS complex, shift of mean electrical axis to the left) and rhythm disturbances such as sinus tacchycardia, atrial fibrillation, atrial premature complexes and atrial Tacchycardia.

A resting ECG trace may show evidence of an enlarge left atrium (Wide P Wave), an enlarged left ventricle (Tall R wave, wide QRS complex, shift of mean electrical axis to the left) and rhythm disturbances such as sinus tachycardia, atrial fibrillation, atrial premature complexes and atrial tachycardia.

===Laboratory Tests===

===Laboratory Tests===

==Prognosis==

==Prognosis==

Mitral Valve Dysplasia can remain asymptomatic for many years (average 4 years). Once congestive heart failure has developed, the progression of the diseae can be monitored by the severity of the clinical signs (cough, exercise intolerance) and radiographically looking at caridac size, the degree of pulmonary oedema and the size of the left atrium. Cardiac size can be measured objectively using the Vertebral Heart Score method.  

Mitral Valve Dysplasia can remain asymptomatic for many years (average 4 years). Once congestive heart failure has developed, the progression of the diseae can be monitored by the severity of the clinical signs (cough, exercise intolerance) and radiographically looking at cardiac size, the degree of pulmonary oedema and the size of the left atrium. Cardiac size can be measured objectively using the Vertebral Heart Score method.  

Mean survival of 200-300 days once in overt cardiac failure with standard treatment protocols.

Mean survival of 200-300 days once in overt cardiac failure with standard treatment protocols.

* Tilley,L.P., Smith, F.W.K, Oyama, M., Sleeper, M. (2007) '''Manual of Canine and Feline Cardiology''' ''Saunders''.

* Tilley,L.P., Smith, F.W.K, Oyama, M., Sleeper, M. (2007) '''Manual of Canine and Feline Cardiology''' ''Saunders''.

[[Category:Cardiovascular_System_-_Developmental_Pathology]][[Category:To_Do_-_Review]]

[[Category:Cardiovascular_System_-_Developmental_Pathology]][[Category:Expert_Review]]