Mitral valve dysplasia

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Advanced mitral dysplasia in a dog[1]

Mitral valve dysplasia is an autosomal-recessive congenital heart disease of dogs characterized by malformation of the mitral valve complex[2].

This defect of the mitral valve leaflets, chordae tendineae or papillary muscles causes mitral valve insufficiency and regurgitation into the left atrium, leading to left atrial and ventricular overload, causing left-sided dilatation, hypertrophic cardiomyopathy, congestive heart failure, arrhythmia and mitral stenosis[3].

Concurrent tricuspid dysplasia[4], hypertrophic cardiomyopathy and subaortic stenosis[5] can occur with this disease.

Canine breeds predisposed include the Bull Terrier, Rottweiler, Newfoundland, German Shepherd and Great Dane.

Clinical signs are normally seen in young dogs (1 - 2 years of age) but can present at an older age with symptoms of generalized weakness, exercise intolerance, syncope, ascites and pale mucus membranes. A cough may be present intermittently.

A tentative diagnosis can be established by auscultation of a holosystolic ejection murmur with radiographic evidence of cardiomegaly. Radiographs usually show left-sided cardiomegaly. Cardiogenic pulmonary edema may also be present.

Definitive diagnosis requires use of M-mode and Doppler echocardiography.

A differential diagnosis would include subaortic stenosis, ventricular septal defect[6], double-chambered right ventricle[7], hyperthyroidism, cardiomyopathy, Duchenne muscular dystrophy, endocarditis, pulmonic stenosis, mitral valve endocardiosis and infections with Dirofilaria spp.

The prognosis for animals with clinical signs of congestive heart failuree is poor, but mildly affected animals may remain free of clinical signs for several years.

Medical therapy is currently the recommended treatment option, consisting of exercise restriction, atenolol, pimobendan[8] and taurine supplementation.

Surgical intervention can be employed in severe cases where financing is not a prohibitive issue. Techniques such as mitral valvular replacement have been employed successfully[9].

References

  1. Cavalier Health
  2. Otoni C & Abbott JA (2012) Mitral valve dysplasia characterized by isolated cleft of the anterior leaflet resulting in fixed left ventricular outflow tract obstruction. J Vet Cardiol 14(1):301-305
  3. De Majo M et al (2003) Hypertrophic obstructive cardiomyopathy associated to mitral valve dysplasia in the Dalmatian dog: two cases. Vet Res Commun 27(1):391-393
  4. Domanjko-Petric A (2004) What is your diagnosis? Mitral and tricuspid dysplasia. J Small Anim Pract 45(2):83-84
  5. Fernández del Palacio MJ et al (1998) Clinical and pathological findings of severe subvalvular aortic stenosis and mitral dysplasia in a rottweiler puppy. J Small Anim Pract 39(10):481-485
  6. Guglielmini C et al (2002) Atrial septal defect in five dogs. J Small Anim Pract 43(7):317-322
  7. Fukushima R et al (2011) Epidemiological and morphological studies of double-chambered right ventricle in dogs. J Vet Med Sci 73(10):1287-1293
  8. Boswood A (2010) Current use of pimobendan in canine patients with heart disease. Vet Clin North Am Small Anim Pract 40:571–580
  9. Behr L et al (2007) Beating heart mitral valve replacement with a bovine pericardial bioprosthesis for treatment of mitral valve dysplasia in a Bull Terrier. Vet Surg 36(3):190-198