To the Editor: We recently published a review (which now features in this issue)1 on the controversies in the definition and management of insignificant left-to-right shunt commonly observed during a routine echocardiographic screening.

As an additional remark, however, we would like to point out an important aspect regarding the echocardiographic definition of restrictive patent foramen ovale (PFO).

Adequate blood flow mixing trough a PFO is essential for survival in neonates and infants with various congenital heart diseases including transposition of the great arteries, hypoplastic left heart syndrome, tricuspid atresia, various forms of univentricular heart, total anomalous pulmonary venous return, etc.2–7

In these diseases signs of PFO restriction should alert the clinician and require urgent Rashkind procedure or anticipation of surgical correction/palliation.2–7

Foramen ovale is easily evaluated by echocardiography.1–7

Echocardiography is also commonly employed to …