Congenital Cardiac Defects in Neonatal Foals: 18 Cases (1992–2007)

Abstract

Background: Literature available regarding congenital cardiac defects in foals is limited to reports of individual cases or small case series.Objective: To describe the clinical, echocardiographic, and necropsy findings and breed predilection of congenital cardiac defects in neonatal foals.Animals: Eighteen foals o15 days of age with 1 or more congenital cardiac defects. Methods: Medical records of foals diagnosed with congenital cardiac defects at the William R. Pritchard Veterinary Medical Teaching Hospital were reviewed. Data collected included history, signalment, clinical signs, laboratory data, diagnostic and necropsy results, and outcome.Results: Arabian foals represented 39% of cases with congenital cardiac defects and were significantly (P 5 .004) overrepresented (OR 5 4.7 [CI: 1.8-12.4]) compared with the general hospital population. Ventricular septal defect (VSD) (14/18), tetralogy of Fallot (5/18), and tricuspid valve atresia (4/18) were the most common defects identified. A !3/6 heart murmur (14/ 14) accompanied by tachycardia (14/17), tachypnea (17/17), and cyanosis of mucous membranes (7/16) were the most common clinical signs. Concurrent congenital defects were common (9/18). Two foals, both with VSD, survived for ! 8 years after diagnosis and 1 was a successful performance horse.Conclusions and Clinical Relevance: Arabian horses appear to have a predisposition for cardiac defects. The presence of a loud murmur (! 3/6), cyanotic membranes, and tachycardia or tachypnea in a neonatal foal should warrant thorough evaluation of the heart for congenital defects. Foals with cardiac defects should be closely evaluated for concurrent congenital defects in other body systems.

Pulmonary atresia with intact ventricular septum and hypoplastic right ventricle in an Arabian foal

“…Valvular abnormalities were identified in 8/18 foals; the tricuspid valve or valvular apparatus were affected in 6/8 foals. Interestingly, Arabians were overrepresented with 35% of the foals belonging to that breed, supporting previous reports in which a higher prevalence of congenital cardiac defects in Arabians was suspected [8]. The occurrence of multiple coexisting congenital cardiac abnormalities is common in horses.…”

“…The occurrence of multiple coexisting congenital cardiac abnormalities is common in horses. In one study, one-third of the foals were found to have multiple concurrent cardiac defects and tachycardia was also a very common clinical finding in affected animals [8].…”

“…Patients affected by these conditions present with stunted growth, exercise intolerance, murmurs, tachycardia, respiratory distress, and cyanosis [4,8]. Hall et al [8] reported that 82% of the foals showed tachycardia on presentation.…”

Quadricuspid aortic valve and a ventricular septal defect in a horse

“…It may occur as a single defect, although it is often encountered in certain congenital syndromes, such as the tetralogy of Fallot [11,15-17]. Arabian horses are predisposed to VSD [9]. Marr [37] reported that Welsh Mountain ponies were more predisposed than Thoroughbreds.…”

“…VSDs are classified according to their location [8]. It is the most commonly diagnosed congenital heart disease in horses, among which Arabian horses exhibit particular predisposition to this disorder [9]. It may occur as a single defect, but it is often a part of a complex congenital anomaly [10-14], among which the best known congenital syndrome is the tetralogy of Fallot [11,15-17].…”