H19 and hypoplastic left heart syndrome: While H19 expression is typically downregulated in adult heart failure of diverse etiologies—including aortic stenosis, hypertrophic obstructive cardiomyopathy, and non-ischemic dilated cardiomyopathy40–42—we show that H19 is selectively upregulated in HLHS hearts, suggesting a unique developmental or stress-response program in this congenital disease.