A CNN investigation calculates that from 2011 to 2013, the program had a 12.5% mortality rate for open heart surgeries,
which is more than three times the national average.
"Why won't they stop?" asked Nneka Campbell, whose baby daughter, Amelia, died after heart surgery at the hospital.
The same day the latest baby died, St. Mary's CEO Davide Carbone wrote a letter to employees about the CNN investigation, which aired Monday night, expressing support for the program and its heart surgeon, Dr. Michael Black.
"The patients we serve are afflicted with severe life-threatening conditions, and it is impossible to eliminate the risk of mortality," he wrote.
The hospital, which is owned by Tenet Healthcare, says CNN did not get the mortality rate right, but won't say what the hospital believes the correct rate is.
"We are deeply saddened when a lack of institutional transparency may have contributed to potentially unnecessary risk and serious harm," said Amy Basken, a spokeswoman for the Pediatric Congenital Heart Association, a national advocacy group.
Last year in April, the Florida Department of Health sent a team of expert heart doctors to St. Mary's to review the children's heart surgery program. The head of the panel, Dr. Jeffrey Jacobs, a professor of cardiac surgery at Johns Hopkins, suggested they stop doing heart surgeries on babies younger than 6 months.
The baby who died Tuesday, Davi Ricardo Brandao, was only a few weeks old when he had surgery in March for a severe heart defect called truncus arteriosus, according to his mother, Pautilia Gomes. She said her son needed a second surgery later that month.
In April, in response to an inquiry from CNN, St. Mary's spokeswoman Shelly Weiss said a patient with truncus arteriosus at St. Mary's was "recovering well and the prognosis is good."
Davi never left the hospital and was not quite 2 months old when he died. Gomes posted a picture on her Facebook page of an eye filled with tears and the word "LUTO," which is Portuguese for "mourning."
According to St. Mary's, the hospital received the experts' final reviews last year in June. In his letter to employees, Carbone said that since that time, "our mortality rate has been consistent with the national average, and does not significantly exceed the mortality rate of other programs as the CNN story alleges."
He did not say what the hospital's mortality rate was, or whether it included Davi's death. An email from CNN to Weiss went unanswered Wednesday.
In his review last year, Jacobs, the Johns Hopkins surgeon, noted that St. Mary's was doing too few pediatric heart surgeries -- a very complex type of operation -- to get good at it. He noted that in 2013, the hospital did 23 procedures. The vast majority of hospitals in the United States that perform these surgeries do more than 100 a year, and anything less than that is considered low volume by the Society for Thoracic Surgeons.
In response to CNN's investigation, Florida's Department of Health and the Agency for Health Care Administration issued a statement Wednesday saying, "Florida does not regulate the number of procedures performed at pediatric cardiac programs" and that the Agency for Health Care Administration "continues to closely monitor St. Mary's to ensure that they are following the law."