Table 1. Clinical classification of congenital, systemic-to-pulmonary shunts associated with pulmonary arterial hypertension (PAH).

Group A. Eisenmenger's syndrome

Eisenmenger’s syndrome includes all systemic-to-pulmonary shunts due to large defects leading to a severe increase in PVR and resulting in a reversed (pulmonary-to-systemic) or bidirectional shunt. Cyanosis, erythrocytosis and multiple organ involvement are present.

Group B. PAH associated with systemic-to-pulmonary shunts

In these patients with moderate-to-large defects, the increase in PVR is mild-to-moderate, systemic-to-pulmonary shunt is still largely present and no cyanosis is present at rest.

Group C. PAH with small defects

In cases with small defects (usually VSD <1 cm and ASD <2 cm of effective diameter assessed by echocardiography), the clinical picture is very similar to idiopathic PAH.

Group D. PAH after corrective cardiac surgery

In these cases, CHD has been corrected but PAH is either still present immediately after surgery or has recurred several months or years after surgery in the absence of significant post-operative residual congenital lesions or defects that originate as a sequelae to previous surgery.

PVR: pulmonary vascular resistance; VSD: ventricular septal defect; ASD: atrial septal defect; CHD: congenital heart disease. Reproduced from [3] with permission from the publisher.