Valvular aortic stenosis

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Aortic stenosis in a dog[1]

Valvular aortic stenosis is a rare congenital heart disease of dogs characterized by malformation of the tricuspid valve complex, systolic regurgitation and right-sided congestive heart failure.

This defect primarily affects large purebred dogs including the Boxer[2] and is not dissimilar clinically from subaortic stenosis[3].

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[4]. In moderate to severe cases, femoral pulse strength is diminished.

A tentative diagnosis can be established by auscultation of a harsh holosystolic ejection murmur at the left cardiac apex[5]. The intensity of the murmur correlates fairly well with the degree of stenosis and may increase as animals mature, reflecting progressive stenosis. Puppies without detectable murmurs should not be considered free of disease until they reach 6 months of age.

Radiographically, there is variable left ventricular enlargement and poststenotic dilatation of the aorta.

Definitive diagnosis requires use of M-mode and Doppler echocardiography[6]. Doppler echocardiography demonstrates severe tricuspid regurgitation and concentric left-sided ventricular hypertrophy[7].

A differential diagnosis would include subaortic stenosis, ventricular septal defect[8], double-chambered right ventricle[9], 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[10] and taurine supplementation.

Surgical intervention can be employed in severe cases where financing is not a prohibitive issue. Balloon valvuloplasty (typically not very effective) and surgical resection have been performed, with variable coutcomes.

References

  1. Vetnext
  2. Höglund K et al (2007) Time-frequency and complexity analyses for differentiation of physiologic murmurs from heart murmurs caused by aortic stenosis in Boxers. Am J Vet Res 68(9):962-969
  3. Chetboul V et al (2006) Congenital heart diseases in the boxer dog: A retrospective study of 105 cases (1998-2005). J Vet Med A Physiol Pathol Clin Med 53(7):346-351
  4. Hoffmann, G et al (2000) Tricuspid valve dysplasia in fifteen dogs. Schweiz Arch Tierheilkd 142:268-277
  5. Höllmer M et al (2008) Aortic stenosis in the Dogue de Bordeaux. J Small Anim Pract 49(9):432-437
  6. Höglund K et al (2007) Contrast echocardiography in Boxer dogs with and without aortic stenosis. J Vet Cardiol 9(1):15-24
  7. Hori Y et al (2008) Evaluation of NT-pro BNP and CT-ANP as markers of concentric hypertrophy in dogs with a model of compensated aortic stenosis. J Vet Intern Med 22(5):1118-1123
  8. Guglielmini C et al (2002) Atrial septal defect in five dogs. J Small Anim Pract 43(7):317-322
  9. Fukushima R et al (2011) Epidemiological and morphological studies of double-chambered right ventricle in dogs. J Vet Med Sci 73(10):1287-1293
  10. Boswood A (2010) Current use of pimobendan in canine patients with heart disease. Vet Clin North Am Small Anim Pract 40:571–580