HLHS, or hypoplastic left heart syndrome, is one of the most complex congenital heart defects and one of the most challenging to manage. In brief, HLHS is a condition in which the left side of the heart never develops nor functions adequately.
Although there is no cure for HLHS, babies born with this once-fatal heart defect now have a chance to live by undergoing a series of three open-heart surgeries or a heart transplant. For more detailed information on HLHS, I recommend the Cincinnati Children's Hospital website.
For videos exploring HLHS prognosis as well as the three stages of surgeries used to manage HLHS, I recommend the University of Pennsylvania Children's Hospital website.