Simple congenital heart defects in humans and animals

Atrial septal defects (ASDs) are one of the most common congenital heart defects, accounting for between 6-10% of congenital heart disease in humans (Silvestry et al., 2015).

Secundum defects are the most common type of ASD in both humans and canines. In canines, some breeds (particularly Boxers) more susceptible than others, although the true incidence of atrial septal defects is unknown as symptoms tend only to emerge secondary to other cardiac problems – such as myxomatous degeneration of the mitral valve (Cavalcanti et al., 2011) – and the ASD is discovered incidentally.

A patent foramen ovale (PFO) is even more common in humans (Silvestry et al., 2015), and can be particularly problematic for racing horses.

Whilst transoesophageal echocardiography (TOE or TEE) remains the gold standard for investigating many cardiac shunts, a large number of defects can be detected using standard transthoracic echocardiography (TTE), particularly when employing microbubbles as contrast agents. Certainly, remodeling (dilatation, hypertrophy) secondary to a long-standing shunt is immediately obvious.