Multifactorial pulmonary hypertension in infantile scimitar syndrome

Pulmonary hypertension in infantile scimitar syndrome is highly prevalent at diagnosis, and has a multifactorial origin.

To analyse the constellation of anatomical anomalies and initial physiology, and their contribution to pulmonary hypertension and outcome in infantile scimitar syndrome.

Pulmonary hypertension causes were classified into five categories: associated with systemic supply to the right lung; associated with left-to-right shunt; postcapillary; related to respiratory or developmental lung disease; and "idiopathic-like" pulmonary arterial hypertension. Co-morbidities contributing to pulmonary hypertension were also classified according to the World Symposium on Pulmonary Hypertension (WSPH) and Panama classifications.

Of 111 patients, 64 had pulmonary hypertension; 24 patients had one cause of pulmonary hypertension, 23 had two potential causes and 17 had at least three potential causes. Co-morbidities contributing to pulmonary hypertension described the multifactorial origin in>80% of patients, with associated congenital heart disease being the main contributor. Mortality was 41% in patients with and 7% in patients without pulmonary hypertension. The proportions of deaths among patients with one, two or more than two causes of pulmonary hypertension were similar. Eight of 38 survivors had persisting pulmonary hypertension at last follow-up. The risk of death was associated pulmonary hypertension at diagnosis (P=0.002) and the presence of an associated congenital heart disease requiring surgical repair (P=0.039).

Scimitar syndrome is an archetypal example of multifactorial causes of pulmonary hypertension, with associated congenital heart disease and pulmonary vascular anomalies being the main contributors. Infants with scimitar syndrome require accurate phenotyping to guide management and predict outcome.