Echocardiographic Features of the Ductus Arteriosus and the Foramen Ovale in a Hospital-Based Population of Neonatal Foals

Abstract

The ductus arteriosus (DA) and foramen ovale (FO), including the septum primum (SP) and septum secundum (SS), are important structures in fetal circulation and are unexplored in neonatal equids. The objective of this study is to describe echocardiographic characteristics in a hospital-based population of neonatal foals. On days 2, 5 and 10 after parturition, cardiac ultrasound was performed, and clinical data were collected in healthy and diseased Warmblood foals. Fifty healthy (n = 15) and diseased (n = 35) Warmblood foals were examined. A left-sided and right-sided holosystolic murmur was audible in 98% (n = 42) and 51% (n = 22), respectively, on day 2; in 81% (n = 25) and 19% (n = 6) on day 5; and in 44% (n = 4) and 11% (n = 1) on day 10. The median grade of the systolic murmurs was higher when the DA was open. Flow through the DA could be visualized with color flow and continuous wave (CW) Doppler from the left parasternal long-axis view of the pulmonary artery in 40/43 foals on day 2, 9/31 foals on day 5 and 2/9 foals on day 10. The DA diameter was 2 ± 1 mm on day 2, 2 ± 1 mm on day 5 and 1 mm on day 10. The thickness of both septa of the FO was similar. The SP fluttered into the left atrium at all ages, but the maximal distance between the SP and SS decreased over time. In conclusion, cardiac murmurs, a patent DA and fluttering FO are frequent findings in neonatal foals. While these findings are probably physiological, the clinical importance needs to be further elucidated.

Keywords: cardiology; equine; neonatology.

Figure 1

Right parasternal four-chamber (R-4C) view of the foramen ovale in a 2-day-old healthy foal. The arrowheads indicate the fluttering septum primum at the base of the ostium of pulmonary vein III (ostium III). The yellow bar indicates a 1 cm distance between the septum primum and septum secundum. LA: left atrium; LV: left ventricle; RA: right atrium; RV: right ventricle.

Figure 2

Septum primum (circle) and limbus (arrowhead) in a 2-day-old healthy foal visualized on a right parasternal oblique view obtained by rotating the ultrasound probe towards two o’clock and angulating dorso-caudally). CaVC: cranial vena cava, CrVC: cranial vena cava, LA: left atrium; RA: right atrium; RV: right ventricle.

Figure 3

Left parasternal long-axis view of the pulmonary artery (PA) using slight dorso-caudal probe angulation in a 2-day-old healthy foal. The internal diameter of the ductus arteriosus is indicated by the yellow bar on the picture insert. The yellow dots indicate the cursos placement for continuous wave Doppler examination. Ao: aorta; PA: pulmonary artery; RV: right ventricle.

Figure 4

Color flow Doppler of the ductus arteriosus (arrowheads) in a 2-day-old healthy foal on the right parasternal slightly cranially angled R-RVOT view. Ao: aorta; PA: pulmonary artery; RA: right atrium; RV: right ventricle.