ISSN 2398-2969      

Atrioventricular valve dysplasia

icanis

Introduction

  • Prevalence: rare.
  • Spectrum of abnormalities: excessively long or short chordae tendinae; abnormal numbers + displacement of papillary muscles; abnormal location of valve annulus; thickened and/or distorted valve cusps. Occasionally mitral valve stenosis, especially Bull Terrier.
  • Signs: valves usually incompetent - one or both may be affected → congestive heart failure - mitral regurgitation may lead to left-sided CHF; tricuspid regurgitation may lead to right-sided CHF.
  • Diagnosis: echocardiography.
  • Treatment: symptomatic.
  • Prognosis: poor if CHF at young age.

Pathogenesis

Etiology

  • Probably hereditary.

Predisposing factors

General

  • Breed.

Pathophysiology

Mitral valve

  • Malformation → valvular incompetence.
  • Rarely, stenotic → greatly increased left atrial pressure.

Mitral dysplasia

  • Mitral regurgitation → left atrial and left ventricular volume overload → left atrial and left ventricular dilation → increased left atrial pressures → pulmonary venous congestion → pulmonary edema (left-sided CHF).
  • If left atrial enlargement is severe enough, arrhythmias such as atrial fibrillation Heart: atrial fibrillation may occur.
  • If severe enough, mitral regurgitation can lead to decreased cardiac output, resulting in weakness or syncope.
  • Severe increases in pulmonary venous pressure may result in pulmonary vasoconstriction → pulmonary hypertension Pulmonary Arterial Hypertension (PHT) and right sided failure secondary to increased afterload on right side of heart.

Tricuspid valve

  • Malformation → valvular incompetence of the valve.
  • Ebstein's anomaly → displacement of the AV leaflets and annulus towards the apex of the heart.

Tricuspid dysplasia 

  • Tricuspid regurgitation → right atrial and right ventricular overload → right atrial and ventricular dilation → increased right atrial pressure → increased central venous pressure Tricuspid valve dysplasia:
    • → pleural effusion
    • → jugular distension and chronic venous congestion of liver → ascites → right-sided CHF.
  • If tricuspid regurgitation is severe enough, it can lead to a decrease in chronic output and result in weakness or syncope.
  • Superventricular tachycardias (including atrial fibrillation Heart: atrial fibrillation ) may be seen.

Timecourse

  • Murmur from birth.
  • Prognosis depends upon severity of the lesion.
  • Patients with AV dysplasia may live years prior to the development of CHF.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Takemura N, Koyama H & Motoyoshi S (1996) Congestive heart failure due to bilateral atrioventricular valve insufficiency in 2 dogs. J V Med Sci 58 (4), 381-384 VetMedResource.
  • White R N, Stepien R L, Hammond R A et al (1995) Mitral valve replacement for the treatment of congenital mitral dysplasia in a bull terrier. JSAP 36 (9), 407-410 PubMed.
  • Lehmkuhl L, Ware A, Bonagura J D (1994) Mitral stenosis in 15 dogs. JVIM (1), 2-17 PubMed.
  • Eyster G E, Anderson L, Evans A T et al (1977) Ebstein's Anomaly - a report of 3 cases in the dog. JAVMA 170 (7), 709-713 PubMed.
  • Liu S & Tilley L P (1976) Dysplasia of the tricuspid valve in the dog and cat. JAVMA 169 (6), 623-630 PubMed.
  • Liu S & Tilley L P (1975) Malformation of the canine mitral valve complex. JAVMA 167 (6), 465-471 PubMed.

Other sources of information

  • Kittleson M & Kienle R (1998) Congenital abnormalities of the atrioventricular valves. In:Small Animal Cardiovascular Medicine, 1st ed.Eds M Kittleson & R Kienle. Mosby, St Louis. pp 273-281.
  • Moise N S (1995) Tricuspid valve dysplasia in the dog. In:Current Veterinary Therapy XII. Bonagura J D (ed). W B Saunders, Philadelphia. pp 813-816.

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