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Degenerative Mitral Valve Disease (view source)
Revision as of 20:18, 9 April 2011
, 20:18, 9 April 2011no edit summary
Blood passes back into the left atrium, compromising the filling from the pulmonary vein, which leads to back pressure on the pulmonary capillaries. Resultant [[Oedema|oedema]] forms in the lungs, and can be heard as moist sounds on auscultation. This reduces the oxygenation of blood leading to exercise intolerance. Failure of the left side eventually compromises the function of the right side. In [[Heart Failure, Right-Sided|right sided heart failure]] there is a pooling of blood in the venous system i.e. in the [[Liver - Anatomy & Physiology|liver]]. In some cases a jet lesion can occur, where a small stream of blood passes back into the left atrium and contacts the atrial wall.
Blood passes back into the left atrium, compromising the filling from the pulmonary vein, which leads to back pressure on the pulmonary capillaries. Resultant [[Oedema|oedema]] forms in the lungs, and can be heard as moist sounds on auscultation. This reduces the oxygenation of blood leading to exercise intolerance. Failure of the left side eventually compromises the function of the right side. In [[Heart Failure, Right-Sided|right sided heart failure]] there is a pooling of blood in the venous system i.e. in the [[Liver - Anatomy & Physiology|liver]]. In some cases a jet lesion can occur, where a small stream of blood passes back into the left atrium and contacts the atrial wall.
[[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.
In advanced cases, signs of right sided congestive heart failure may follow due to an increased pressure load on the right ventricle as a result of long standing pulmonary congestion.
In advanced cases, signs of right sided congestive heart failure may follow due to an increased pressure load on the right ventricle as a result of long standing pulmonary congestion.
==Signalment==
Endocardiosis tends to affect middle-aged and older dogs, with males being predisposed. Breeds with particular predisposition to the disease include smaller breeds
such as Chihuahuas, Boston Terriers, Poodles, Pomeranians, Cavalier King Charles Spaniels and larger breeds such as the German Shepherd. It is the most common heart condition in dogs. In dogs over 9 years old 97% show lesions, of which approximately 40% are clinically significant. The condition is often found at post mortem as an incidental age related change. The disease is rare in cats.
Typically in middle aged to older small breed dogs. Genetically predisposed breeds include Cavalier King Charles Spaniel, Bull Terriers, German Shepherds, and Great Danes.
Typically in middle aged to older small breed dogs. Genetically predisposed breeds include Cavalier King Charles Spaniel, Bull Terriers, German Shepherds, and Great Danes.
===History===
===History===
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.
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 ==
Signs depend on stage of disease, but may include coughing, syncope, weight loss, pale or cyanotic mucus membranes and prolonged capillary refill time. If [[Heart Failure, Left-Sided|left sided heart failure]] is present then signs will also include exercise intolerance, weakness, dyspnoea, inappetance and lethargy. If right sided heart failure is present then signs including hepatomegaly, jugular pulses & distension, pleural effusion, ascites and peripheral oedema will occur.
* Left apical systolic murmur
* Left apical systolic murmur
* Left sided congestive heart failure
* Left sided congestive heart failure
** 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
== Diagnosis ==
Clinical signs plus signalment of the dog are indicative of the disease. Upon physical examination a '''murmur over the left heart apex''' may be heard. Snaps, crackles, pops will also be heard if pulmonary edema is present. Muffled heart sounds in the presence of pleural/pericardial fluid will be auscultated.
Upon '''radiography''' there will be visible signs of left sided heart enlargement. There will possibly be none, some or all of the following radiographic signs - 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 and right-sided signs (distended caudal vena cava, ascites, pleural effusion, hepatomegaly).
'''Electrocardiography''' (ECG) may show a left atrial enlargement pattern, left ventricular enlargement pattern and rhythm disturbances (supraventricular [[:Category:Arrhythmia|arrhythmias]]: atrial premature complexes, atrial tachycardia, and ventricular rhythm disturbances).
'''Echocardiography''' may detail 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) and left ventricular dilation (tall R wave, wide QRS complex). Dopper will demonstrate the presence of regurgitative flow. On M wave echography there may be a normal to increased fractional shortening of the myocardium in early stages of the disease and a decreased fractional shortening of the myocardium in later stages of the disease.
===Diagnostic imaging===
===Diagnostic imaging===
Pro-brain natriuretic peptide (N-BNP) is a newly described cardiac hormone considered to be an effective marker of severity and prognosis of acute coronary syndromes and congestive heart failure. Circulating levels of the hormone increase in peripheral blood with increased myocardial stress. Commercial assays are not currently available.
Pro-brain natriuretic peptide (N-BNP) is a newly described cardiac hormone considered to be an effective marker of severity and prognosis of acute coronary syndromes and congestive heart failure. Circulating levels of the hormone increase in peripheral blood with increased myocardial stress. Commercial assays are not currently available.
==Treatment==
== Treatment ==
If animal is presented in left or right sided heart failure treatment is given at the onset of clinical signs. Such treatments include ACE inhibitors and diuretics.
If the disease is detected but the animal is not yet in heart failure then no treatment is required. Exercise must also be restricted and special formulated sodium reduced cardiac diets recommended.
Symptomatic treatments are also given if clinical signs persist while the animal is on heart failure medications.
No treatment is recommended prior to the onset of heart failure. Once there is evidence of congestive heart failure, treatment is aimed at its management through a combination of drugs.
No treatment is recommended prior to the onset of heart failure. Once there is evidence of congestive heart failure, treatment is aimed at its management through a combination of drugs.
5. '''Control cardiac arrhythmias using anti-arrhythmic drugs
5. '''Control cardiac arrhythmias using anti-arrhythmic drugs
==Prognosis==
== Prognosis ==
Asymptomatic patients may live for many years. Once heart failure occurs, life expectancy is usually around one year although some patients remain stable for years on heart failure medications.
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.
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 is 200-300 days once in overt cardiac failure with standard treatment protocols.
Mean survival is 200-300 days once in overt cardiac failure with standard treatment protocols.
== Test yourself with the Endocardial Pathology Flashcards ==
[[Endocardial Pathology Flashcards]]
==Literature Search==
==Literature Search==
* Tilley, L.P. and Smith, F.W.K.(2004) '''The 5-minute Veterinary Consult (Third edition)''' ''Lippincott, Williams & Wilkins''.
* Tilley, L.P. and Smith, F.W.K.(2004) '''The 5-minute Veterinary Consult (Third edition)''' ''Lippincott, Williams & Wilkins''.
* 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''.
== References ==
Ettinger, S.J. and Feldman, E. C. (2000) Textbook of Veterinary Internal Medicine Diseases of the Dog and Cat Volume 2 (Fifth Edition), W.B. Saunders Company
Ettinger, S.J, Feldman, E.C. (2005) Textbook of Veterinary Internal Medicine (6th edition, volume 2), W.B. Saunders Company
Fossum, T. W. et. al. (2007) Small Animal Surgery (Third Edition), Mosby Elsevier
[[Category:Cardiovascular_System_-_Degenerative_Pathology]] [[Category:Endocardial_Pathology]] [[Category:Expert_Review]] [[Category:Cardiac_Diseases_-_Cat]] [[Category:Cardiac_Diseases_-_Dog]]
[[Category:Cardiovascular_System_-_Developmental_Pathology]][[Category:To Do - _Review]]
[[Category:Cardiovascular_System_-_Developmental_Pathology]][[Category:To Do - _Review]]
[[Category:Cardiac Diseases - Dog]]
[[Category:Cardiac Diseases - Dog]]