Partial atrioventricular septal defect in an adult sport horse.

The research article is about an adult sport horse diagnosed with a partial atrioventricular septal defect, a heart condition. Despite this diagnosis, the horse was still being used for showjumping without displaying any signs of illness or difficulty, three years after the initial detection.

Objective of the Research

The research aimed to provide a detailed clinical account of an adult sport horse diagnosed with a specific heart defect known as a partial atrioventricular septal defect. The horse was able to perform regular activities without any visible signs of disease or distress, thus undermining common assumptions about this condition’s severity in horses.

Case Presentation

• The nine-year-old horse was initially examined due to persistent coughing. A serious heart condition, described as a partial atrioventricular septal defect, was inadvertently identified.
• The particular condition represented a large, ostium primum atrial septal defect with shared atrioventricular valve leaflets and a cleft leaflet of the mitral valve.
• The horse exhibited a left-sided grade 4/6 holosystolic (band-shaped) murmur and right-sided grade 3/6 murmur. Echocardiography showed bidirectional shunting through a 6.4 cm communication in the ventral atrial septum, another sign of the ostium primum atrial septal defect.

Additional Findings

• The researchers identified additional cardiac abnormalities, including a hypertrophic septomarginal trabecula, a thickened tricuspid valve, moderate mitral and tricuspid regurgitation due to leaflet prolapse, mild aortic regurgitation, and signs of moderate right ventricular volume overload.
• However, despite these observations, the horse showed no signs of arrhythmia, neither at rest nor during exercise, as seen on the electrocardiography.
• The horse continued to show jumping without any signs of disease or exercise intolerance.

Three-Year Follow-up

• A follow-up examination was performed three years after initial presentation. The contrast echocardiography confirmed the presence of right-to-left shunting via the atrial septal defect.
• There was an increase in the left ventricular internal diameter based on M-mode echocardiography compared to the initial examination.
• Occasional ventricular premature depolarizations were identified on the resting and exercise electrocardiogram.
• The case represents the first description of a clinically asymptomatic partial atrioventricular septal defect in an adult sport horse.