Pulmonic stenosis

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Right ventricular hypertrophy associated with pulmonic stenosis in a dog[1]

Pulmonic stenosis (Right ventricular outflow tract obstruction) is an relatively common congenital heart disease of dogs characterized by narrowing of the pulmonary valve and subsequent juvenile-onset right-sided congestive heart failure and sudden death.

The English Bulldog[2], Chihuahua, Beagle[3], Bull Mastiff[4], Fox Terrier, Samoyed, Cocker Spaniel and West Highland White Terrier breeds are predisposed.

A hereditary form has been detected in the Boykin Spaniel[5].

The degree of hypertrophy is related to the severity of the stenosis. The resulting ventricular lumen is decreased in size and the right ventricle has reduced diastolic compliance and filling capacity. The disease causes pressure overload and concentric hypertrophy of the right ventricle. Dogs with mild to moderate stenosis may remain asymptomatic for years.

Concurrent congenital disease also occurs with this condition, including patent foramen ovale[6] and pectus excavatum[7].

The defect causes clinical and pathophysiologic signs similar to those of congenital double-chambered right ventricle in dogs but has distinct diagnostic features[8].

Affected young pups (from 12 weeks of age) may have stunted growth, pot-bellied appearance, but many have only mild stenosis and may be asymptomatic. However, in moderate to severe cases, clinical signs are usually evident, with generalized weakness, exercise intolerance, syncope, pale mucus membranes and progressive ascites. A cough may be present intermittently.

A tentative diagnosis can be established by auscultation of a high-pitched ejection murmur heard best at the left base close to the sternum.

There may be radiographic evidence of cardiomegaly and pulmonary edema, but definitive diagnosis requires use of M-mode and Doppler echocardiography or angiocardiography. On echocardiography, right-sided heart enlargement, post-stenotic dilation of the main pulmonary artery and right ventricular hypertrophy may be present[9].

On ECG examination, ventricular tachycardia may sometimes be evident.

A differential diagnosis would include ventricular septal defect[10], atrial septal defect[11], hyperthyroidism, cardiomyopathy, Duchenne muscular dystrophy, endocarditis, mitral valve endocardiosis and infections with Dirofilaria spp.

Treatment is usually conservative in cases with mild clinical signs, with management of secondary cardiogenic pulmonary edema. Dogs with mild to moderate stenosis can have well-compensated disease and live a normal life span. Doppler-derived right ventricular to pulmonary artery pressure gradients of < 50 mmHg are considered mild and are associated with a favorable prognosis. Pressure gradients > 60 mmHg are indicative of moderate disease and a poorer prognosis without surgical intervention[12][13]. These echocardiographic features may be used in dog breeding programs to reduce the prevalence and severity of this cardiac defect[14].

In cases of severe stenosis, severe right ventricular hypertrophy, or in uncompensated patients, balloon valvuloplasty is the treatment of choice[15], but surgical correction can also be achieved by valvotomy, via open pulmonary valve commissurotomy, with/without biomembrane patch grafting, under cardiopulmonary bypass[16].

References

  1. Marvista Vet
  2. Tidholm A (1997) Retrospective study of congenital heart defects in 151 dogs. J Small Anim Pract 38:94–98
  3. Patterson DF et al (1981) Hereditary dysplasia of the pulmonary valve in Beagle dogs. Pathologic and genetic studies. Am J Cardiol 47:631–641
  4. Malik R et al (1993) Valvular pulmonic stenosis in bull mastiffs. J Small Anim Pract 34:288–292
  5. Jacobs G et al (1990) Valvular pulmonic stenosis in four Boykin Spaniels. J Am Anim Hosp Assoc 26:247–252
  6. Fujii Y et al (2012) Prevalence of patent foramen ovale with right-to-left shunting in dogs with pulmonic stenosis. J Vet Intern Med 26(1):183-185
  7. Fournier TE (2008) Dynamic right ventricular outflow tract (infundibular) stenosis and pectus excavatum in a dog. Can Vet J 49(5):485-487
  8. Martin JM et al (2002) Surgical correction of double-chambered right ventricle in dogs. J Am Vet Med Assoc 220(6):770-774
  9. Buchanan JW (1990) Pulmonic stenosis caused by a single coronary artery in dogs: Four cases (1965–1984). J Am Vet Med Assoc 196:115–120
  10. Guglielmini C et al (2002) Atrial septal defect in five dogs. J Small Anim Pract 43(7):317-322
  11. Fukushima R et al (2011) Epidemiological and morphological studies of double-chambered right ventricle in dogs. J Vet Med Sci 73(10):1287-1293
  12. Francis AJ et al (2011) Outcome in 55 dogs with pulmonic stenosis that did not undergo balloon valvuloplasty or surgery. J Small Anim Pract 52(6):282-288
  13. Johnson MS et al (2004) Pulmonic stenosis in dogs: Balloon dilation improves clinical outcome. J Vet Intern Med 18:656–662
  14. Menegazzo L et al (2012) The relevance of echocardiography heart measures for breeding against the risk of subaortic and pulmonic stenosis in Boxer dogs. J Anim Sci 90(2):419-428
  15. Johnson MS et al (2004) Pulmonic stenosis in dogs: Balloon dilation improves clinical outcome. J Vet Intern Med 18:656–662
  16. Fujiwara M et al (2012) Surgical treatment of severe pulmonic stenosis under cardiopulmonary bypass in small dogs. J Small Anim Pract 53(2):89-94