Table 1. Study population.

n	37
Age (years)	Median: 6 years (range: 3 days-17 years, IQR: 264 days-12 years)
Female sex % (n)	38% (14)
Race % (n)
White	68% (25)
Black	27% (10)
Asian	3% (1)
Other	3% (1)
Weight (kg)	Median: 18.7 kg (range: 2.2-90, IQR: 7.7-47.4)
Height (cm)	112 cm (range: 47-182, IQR: 66-157)
Diagnosis
Myocarditis	38% (14)
Congenital heart disease*	27% (10)
Dilated cardiomyopathy	11% (4)
Status post heart transplant	11% (4)
Hypertrophic cardiomyopathy	3% (1)
Restrictive cardiomyopathy	3% (1)
Other**	8% (3)
Indication for mechanical support
Elective or semi-elective	35% (13)
Following cardiac arrest	62% (23)
Failure to separate from CPB	3% (1)
Time on ECMO prior to ASD procedure	Median: 0 (Range: 0-2, IQR: 0-1)
Indication for creation of atrial communication
Clinical suspicion of imminent LA hypertension	32% (12)
Evidence of LA hypertension on TTE	30% (11)
Pulmonary edema	22% (8)
Pulmonary hemorrhage	14% (5)
Elevated LA pressure prior to ECMO	3% (1)
Total duration of mechanical support (days)	Median: 7 (Range: 2-123, IQR: 5-10)

^*Diagnoses include congenital mitral stenosis with mechanical prosthesis (n=2) and transposition of the great arteries after arterial switch operation (n=2), as well as anomalous left coronary from the pulmonary artery with bypass graft, bicuspid aortic valve with aortic insufficiency, critical coarctation of the aorta, tetralogy of Fallot, tetralogy of Fallot pulmonary atresia, and incomplete atrioventricular canal with left atrioventricular valve regurgitation

^**Includes multi-organ system failure due to hemophagocytic lymphohistiocytosis, myocardial infarct of unknown etiology, and transient cardiac dysfunction in a child with very long chain acyl-coenzyme A dehydrogenase deficiency