Simply put, one side of her heart is underdeveloped, which means that the other chamber has to do the work of both. She still faces a third operation, which Jimmy Koontz told me doctors at the Nemours Cardiac Center of the Alfred I. duPont Hospital for Children in Delaware hope can be put off until she's at least 2.
It could have been worse, they have told me. After a sonogram detected a growth called a cystic hygroma on the back of the unborn baby's neck, doctors said there could be severe chromosomal damage.
When it turned out to be "only" a heart problem, the Koontzes were relieved because while HLHS is incurable, surgery can help.
But none of this medical care, including a helicopter ride from Pennsylvania to Delaware after she was born, is cheap, and the Koonztes are not rich.
Jimmy works at Ski Liberty near Rouzerville, Pa., while his wife stays home and cares for Alivia.
On Christmas morning, the furnace died. In January, a deer danced into the path of his 1978 Chevrolet four-wheel-drive pickup, which he's since replaced, in part with donations from generous readers of The Herald-Mail.
And so they press on, dealing with insurance companies, doctor visits and up-and-down emotions, sustained by what they say is faith and the help of friends and family.
Both groups were there in abundance on Saturday, waiting patiently for the food and for a chance to see Alivia, who was being carried from table to table by Angie's sister, Rhonda Uzelac.
As Uzelac rocked Alivia in an effort to coax a smile, Angie Koontz told me that the baby is making some progress.
"She is talking. She tries to repeat anything you say. She's saying Da-da, Ma-ma and Ba-ba. I'm starting to teach her a little bit of sign language because she gets so frustrated that she can't tell you what she wants," she said.
The baby is sitting up by herself, but not yet crawling, her mother said. She weighs just 14 pounds and has had problems putting on weight.
"That could be part of the reason she doesn't want to be on her belly. She may not have the strength in her arms to raise up," Alivia's mother said.
To help with her development, Uzelac said that Alivia is going to the Early Intervention Program run by the Washington County Board of Education.
I asked Jimmy Koontz, the more reserved of the two parents, how he felt about everything that's happened up to this point.
"I'm just happy we made it to her first birthday. The doctors are happy with her progress," he said.
As noted previously, the cost of all of this can seem staggering. With gasoline topping $2 a gallon, it's not cheap to drive to doctor visits in Harrisburg, Pa.
Many have also pitched in to assist the family, but a few more dollars wouldn't hurt, either.
If you can help, consider sending a check to Shiloh United Methodist Church, 19731 Shiloh Church Road, Hagerstown, MD 21742.
Bob Maginnis is Opinion Page editor of The Herald-Mail.