Complete atrioventricular canal defect in a foal: Clinical and pathological features

Area of Science:

• Veterinary Cardiology
• Congenital Heart Disease
• Equine Health

Background:

• Atrioventricular (AV) canal defects are rare congenital heart anomalies resulting from abnormal endocardial cushion development.
• These defects involve complex malformations of the atrial septum, ventricular septum, and AV valves, potentially leading to severe heart failure.

Purpose of the Study:

• To document the clinical, diagnostic, and pathological findings of a complete AV canal defect in a young foal.
• To investigate the cardiopulmonary consequences, including congestive heart failure and pulmonary hypertension, associated with this defect.

Main Methods:

• Case report of a six-week-old Thoroughbred foal presenting with persistent tachypnea and tachycardia.
• Diagnostic methods included clinical examination, echocardiography, cardiac catheterization, and gross and histopathologic examination of the heart and lungs.

Main Results:

• Findings were consistent with a complete AV canal defect, characterized by a large septal defect, common atrioventricular orifice, and anomalous valve leaflets.
• The foal exhibited bi-directional shunting, congestive heart failure, and pulmonary hypertension with associated medial hypertrophy of pulmonary arterioles.

Conclusions:

• This case highlights a complete endocardial cushion defect in a foal, leading to significant cardiovascular compromise.
• The study underscores the link between AV canal defects, anomalous atrioventricular valve development, and the subsequent development of pulmonary hypertension and heart failure in equine patients.