Canis ISSN: 2398-2942

Heart: rupture of chordae tendinae

Introduction

  • Cause: myxomatous degeneration (valvular endocardiosis) of mitral valve and chordae tendinae.
  • Signs: acute onset dyspnea due to sudden pulmonary edema. New or changed character of mitral regurgitation murmur.
  • Diagnosis: radiography, ultrasonography.
  • Treatment: emergency → stabilize patient. Once stable, manage as for severe mitral endocardiosis.
  • Prognosis: high mortality. Poor for medium-term survival with fair quality of life.

Pathogenesis

Etiology

  • Degenerative process of collagen and glycosaminoglycans in valve leaflets and chordae tendinae.

Predisposing factors

General
  • Breed.
  • Age.
  • Sex.
  • Size? (Larger dogs).

Specific

  • Sudden exertion.
  • Trauma?

Pathophysiology

  • Myxomatous degeneration of mitral valve leaflets and associated chordae tendinae
  • Mitral regurgitation and mitral prolapse usually present as a result of mitral endocardiosis before ruptured chordae tendinae.
  • Increased systolic pressure gradient across incompetent mitral valve may be exacerbated by exertion or perhaps thoracic trauma.
  • One of the chordae tendinae may rupture → dramatic increase in severity of mitral regurgitation (and altered character of heart murmur ).
  • Sudden increase in left atrial/left ventricular volume overload cannot be accommodated by dilatation of the left atrium and left ventricle in the acute setting → sudden increase in left atrial and left ventricular end-diastolic pressures.
  • Increased left atrial pressure → increased pulmonary venous pressure → increased pulmonary capillary (wedge) pressure → extravasation of fluid from capillaries.
  • Pulmonary edema often alveolar in acute setting → expectorated with pulmonary surfactant (pink-white froth).
  • Alveolar flooding and interstitial oedema and resulting decreased lung compliance → dyspnea.
  • Sudden increase in left ventricular end-diastolic pressure causes increased wall stress (by La Place relationship ) → may result in ventricular arrhythmias.
  • Sudden increase in left atrial pressure causes left atrial stretch → may result in supraventricular arrhythmias.
  • Severity of signs depends on whether a primary chordal rupture (may result in sudden death) or a secondary or tertiary chordal rupture (less severe pulmonary edema - may present as just mitral endocardiosis).

Timecourse

  • Even if patient can be stabilized in the short-term, usually dies within 6 months maximum.

Diagnosis

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Treatment

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Jacobs G J, Calvert C A, Mahaffrey M B & Hall D G (1995) Echocardiographic detection of flail left atrioventricular valve cusp from ruptured chordae tendinae in four dogs. JVIM 9 (5), 341-346 VetMedResource.
  • Ettinger S J & Buergelt C D (1969) Ruptured chordae tendinae in the dog. JAVMA 155 (3), 535-539 PubMed.


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