Endocardial fibroelastosis in a quarterhorse mare.

The research article provides an account of a rare case of heart disease, called endocardial fibroelastosis, in a 4-year-old Quarterhorse mare. This illness became evident through a myriad of symptoms such as weight loss, loss of appetite, lethargy, diarrhea, colic, a considerably enlarged heart and congested blood vessels.

Clinical History

• The research begins by outlining the clinical history of the Quarterhorse mare. She was presented to the Clemson Veterinary Diagnostic Center with a chronic medical history of inappetence, weight loss, and lethargy — a state of weariness that involves reduced energy, physical or mental exhaustion, and lack of motivation. The condition deteriorated to include mild diarrhoea and signs of colic prior to the horse’s death.

Necropsy Examination

• In order to determine the cause behind these various symptoms, the researchers performed a necropsy examination post-mortem. The most critical discovery during this examination was the mare’s significantly enlarged heart, the major reason for which was identified as marked dilation (expansion) of the right atrium — one of the four chambers in the heart.
• Additional abnormalities included tortuous, or twisted, congested mesenteric blood vessels, pronounced ascites which is an abnormal build-up of fluid in the abdomen, pleural effusion denoting the excess fluid that fills the pleural cavity surrounding the lungs, and pulmonary oedema, which is basically fluid accumulation in the tissue and air spaces of the lungs.

Diagnosis

• The examination of the heart revealed diffusion, or spreading, of thickening in the endocardium on the left side of the heart along with the mitral valve leaflets. This valve controls the blood flow between the left atrium and left ventricle in the heart.
• On microscopic analysis, researchers discovered that the cause of the endocardial thickening was the deposition of fibrous connective tissue and elastin fibers. Elastin is a highly elastic protein that allows many tissues in the body to resume their shape after stretching or contracting.
• The culmination of all these findings led the researchers to diagnose the Quarterhorse mare with endocardial fibroelastosis, a rare heart disease primarily seen in children and occasionally in dogs, but rarely in horses. This condition causes increased thickening due to fibrous tissue in the innermost layer of the heart.