Table 1.

Nice 2013 World Symposium on Pulmonary Hypertension’s Clinical Classification of Congenital Systemic-to-Pulmonary Shunts Associated with Pulmonary Arterial Hypertension

A. Eisenmenger syndrome	Includes all large intra- and extra-cardiac defects which begin as systemic-to-pulmonary shunts and progress with time to severe elevation of pulmonary vascular resistance (PVR) and to reversal (pulmonary-to-systemic) or bidirectional shunting; cyanosis, secondary erythrocytosis and multiple organ involvement are usually present.
B. Left-to-right shunts	Correctable Noncorrectable Include moderate to large defects; PVR is mildly to moderately increased systemic-to-pulmonary shunting is still prevalent, whereas cyanosis is not a feature
C. PAH with coincidental CHD	Marked elevation in PVR in the presence of small cardiac defects, which themselves do not account for the development of elevated PVR; the clinical picture is very similar to idiopathic PAH. To close the defects is contraindicated.
D. Post-operative PAH	Congenital heart disease is repaired but PAH either persists immediately after surgery or recurs/develops months or years after surgery in the absence of significant postoperative hemodynamic lesions. The clinical phenotype is often aggressive.

PAH, pulmonary arterial hypertension; PVR, pulmonary vascular resistance; CHD, congenital heart disease. Reproduced from¹⁷ with permission.