But the latest available data suggests that the facility, which describes itself as the only complete cardiac program for kids north of Boston, has failed to live up to that promise.

An analysis of four years of data ending December 2015 indicates that Bush’s parent institution, Maine Medical Center, had point estimates of surgical mortality that were more than two times higher than expected for their overall program and in four of five categories of congenital heart surgery. However, because Maine’s surgeons operate on a small number of patients, these findings were only statistically significant overall and in one of the five categories. In that category, the death rate was more than four times higher than expected, according to data from The Society of Thoracic Surgeons, or STS, Congenital Heart Surgery Database.

Maine Medical Center is one of 14 U.S. hospitals tagged with one of three possible stars – the lowest rating – in the latest study of death rates for congenital heart surgery based on STS data. To their credit, Maine Medical and two other one-star facilities allowed the society to publicly post their high mortality scores. The others are Children's Hospital of The King's Daughters, in Norfolk, Virginia, and Nationwide Children's Hospital in Columbus, Ohio.

The other 11 high-mortality hospitals do not reveal their numbers. Under the terms of its agreements with hospitals, the society can't release a hospital's star rating or data without the hospital's consent. As a result, parents of congenital heart surgery patients at those hospitals may not know that their children are at higher risk.

Nor will referring physicians necessarily realize it.

"You don't know what you're getting if they're not reporting their data," says Dr. Jeffrey Jacobs, chief of cardiac surgery at Johns Hopkins All Children's Hospital in St. Petersburg, Florida, and chairman of the STS Workforce on National Databases.

Not even the Society of Thoracic Surgeons leaders who run the congenital heart surgery public-reporting project can peer behind the curtain. Only the center where the data is analyzed, the Duke Clinical Research Institute, and the hospitals know their scores. And Duke isn't allowed to say.

"We can't peek into the database," says Dr. David Shahian, a professor of surgery at Harvard Medical School and chairman of the STS Quality Measurement Task Force. "The results are owned by STS participants. They can do with them what they want."

This week in Denver, the Pediatric Congenital Heart Association – a proponent of performance measurement and public reporting – is holding its third summit focusing on public reporting and transparency involving pediatric and congenital heart disease outcomes.

Amy Basken, the organization's director of programs, says the information is vital for parents trying to figure out where to turn for help.

"It's not fair that anyone who works in a hospital can use connections to determine where to get the best care. That's not available to the average parent," says Basken, the parent of an 11-year-old boy still struggling with health challenges linked to a congenital heart defect fixed days after his birth. "The remedy is public reporting."

In recent years, deaths reported at two children's hospitals crystallized the importance of tracking and publicly reporting on the quality of care at children's institutions:

In 2012, Kentucky Children's Hospital halted heart surgeries in a move coinciding with the reported deaths of two babies who had been operated on and problems suffered by two more. The hospital since has declined to supply U.S. News with a total number of deaths during the corresponding period, instead repeating a previous assertion that its death rate for the heart program was 7.1 percent. Last January, Kentucky Children's finalized a pediatric heart surgery partnership with Cincinnati Children's Hospital Medical Center. And on Dec. 1, Dr. James Quintessenza took over as chief of pediatric cardiothoracic surgery at Kentucky Children's, Cincinnati Children's spokesman Terry Loftus says. Although his primary appointment will be at Cincinnati Children's, Quintessenza will be based in Lexington, Kentucky, and work in the hospital there. Surgery at Kentucky Children's is still on hold, Loftus says.

Problems also surfaced at St. Mary's Medical Center in West Palm Beach, Florida, with nine babies reportedly dying between 2011 and 2015 after surgeries there. The hospital disputed a CNN report about its mortality rate and said STS data indicated that its congenital heart surgery death rate was within the expected range. Nevertheless, St. Mary's has stopped performing complex heart procedures, spokesman Ryan Lieber says. A series of site visits by specialists included an analysis by Jacobs, of All Children's, who reported that surgeons were performing heart procedures so rarely that they couldn't sustain their skill level. It is "unlikely that any program" could reach and sustain high standards of performance when performing less than two heart operations per month, Jacobs concluded in his report to the Florida Agency for Health Care Administration.

It's rare that such cases make headlines, however. And despite the media coverage, these institutions still have not disclosed critical details about what, if anything, went wrong. Some higher-mortality hospitals, meanwhile, may not know they have a problem. Those that do, and fail to acknowledge it, typically carry on as usual, promoting their services and seeking new patients.

If a hospital doesn't publicly display its STS data, parents should demand the information, Shahian says: "We encourage parents or patients always to ask their potential heart surgery provider to show them their results. If they say they're not in STS and not collecting those results, it's a problem. If they're reluctant to show you their STS results, that's also a problem."

Asking for numbers is "a reasonable request that no reasonable surgeon should refuse," Shahian says.

All three of the one-star hospitals that do reveal their numbers have taken steps to improve their surgical care. Maine Medical Center officials declined a request for an interview on the hospital's rating, but the hospital announced in September that it had appointed a chief quality and safety officer, Dr. Omar Hasan, recruited from the American Medical Association. In a statement to U.S. News, the hospital also reaffirmed its commitment to performance measurement and public reporting, adding that a year ago, Maine's "Cardiovascular Institute and Barbara Bush Children's Hospital developed a program to enhance quality outcomes among our patient population in partnership with our medical staff and care teams."

James Dahling, CEO of Children's Hospital of The King's Daughters, says his hospital has joined forces with the University of Virginia Health System to improve its pediatric heart surgery, which may be offered in Norfolk or at the University of Virginia Children's Hospital in Charlottesville to best meet a child's needs.

"What we're most concerned about is the best way to treat the child," Dahling says. "How can we get the best outcomes? What's the best way to support the families?"

And Nationwide, long recognized for excellence, has stepped up the training and mentoring of newly hired surgeons and other staff.

"Of course I'm disappointed that we weren't shining," says Dr. Mark Galantowicz, co-director of Nationwide's Heart Center. Galantowicz blames the hospital's slide on a single year marred by "suboptimal" care provided by new personnel. He declined to offer specifics.

"Every program goes through ebbs and flows," he says. "It may be a new surgeon, a new procedure or changes in an [intensive care unit]. It's important to stay on top of those things, flush them out and improve."

A congenital heart problem – broadly meaning a heart that doesn't develop fully or properly in the womb – is the most common form of birth defect, affecting about 1 in every 100 newborns and approximately 40,000 babies each year in the U.S. Doctors have documented 38 classes of congenital problems that affect different parts of the heart to varying degrees.

In mild cases, the heart may fix itself. In other cases, surgery is required. Some procedures involve multiple repairs over years, and many challenge the skills even of experienced surgeons. An infant's heart is about the size of its fist, with blood vessels thinner than bakery string. A mistake may be fatal, while doing nothing can be fatal, too. The most severe defects, such as hypoplastic left heart syndrome, or HLHS, are deadly without surgery.

Fixing HLHS takes three carefully staged procedures over two years. The first of these procedures – called the Norwood – has the third-highest death rate of 100 congenital heart operations, according to a ranking by The Society of Thoracic Surgeons and the European Association for Cardio-Thoracic Surgery. Its steps include constructing a larger aorta and removing an atrial wall.

Top-notch care is critical for these patients, experts say, as many children with congenital heart disease can't survive two weeks without lifesaving surgery. And studies confirm that performance varies widely between hospitals. A study published in 2012 of more than 58,000 heart operations at 73 hospitals found that the best-performing hospitals had estimated death rates as low as 6.5 percent. The worst had death rates approaching 40 percent.

Today, consumer demand for transparency has prompted a growing number of hospitals to publicly report on their performance, good or bad, in a step many once considered unthinkable. When a hospital's performance ebbs, the data help diagnose the problem and point to a remedy.

For years, this type of information was scattered in confidential patient records, depriving people of a chance to assess the quality of a hospital's care. Hospitals were similarly unable to tell how they measured up against other hospitals.

Other rankings and ratings cropped up to fill the gap, including the U.S. News Best Children's Hospital Rankings, which are based on an extensive survey of clinical data voluntarily provided by participating hospitals. The U.S. News rankings offer consumers a tool for deciding where to seek the highest quality of care.

However, the U.S. News rankings don't highlight hospitals that provide risky care, as the STS Congenital Heart Surgery Database does. A U.S. News decision to give extra credit for transparency to hospitals that allow the society to post their data has helped prod more hospitals to participate in the organization's public reporting program, says Jacobs, who also leads the cardiology and cardiac surgery working group for the Best Children's rankings.

Since January 2015, the percentage of hospitals participating in the STS database who allow their information to be posted publicly has increased from 23 percent to almost 60 percent.

"A hospital with a three-star rating has a lower mortality than expected, and a hospital with a one-star rating has a higher mortality than expected," Jacobs says.

To assure accuracy, the STS analysis relies on a model that takes into account the riskiness of the operation and the hospital's mix of patients to adjust for the fact that some hospitals attract more patients with complex conditions than others.

"It's the best risk model ever used in pediatric heart surgery," Jacobs says. "If we take into account the hospital's overall case mix, we can determine the expected mortality of that hospital."

The analysis also involves a strict test of statistical confidence to assure that there's at least a 95 percent likelihood that the result is accurate.

Top Hospitals Had High Patient Volumes and Fewer Deaths Than Expected

Hospital 4-Year Total Patients 4-Year Actual Deaths 4-Year Expected Deaths* Texas Children's 2454 39 78 Phoenix Children's 1512 25 46 Children's Hospital of Wisconsin 1410 26 48 Ann & Robert H. Lurie Children's 1205 18 29 Advocate Children's 1189 21 41 MUSC Children's 1187 23 38 Le Bonheur Children's 1039 17 35 Penn State Hershey Children's 616 7 18

Society of Thoracic Surgeons (STS) data from 2012 to 2015 show that all but one of the eight hospitals granted the top rating of three stars were high-volume centers.

*The number of expected deaths was calculated using the expected mortality rate provided by the STS in relation to the number of observed deaths and the observed mortality rate.

Sources: STS, U.S. News analysis

In Maine Medical Center's case, the model takes into account 269 patients who visited during the four years ending in December 2015. While the pool may include adult patients, "the overwhelming majority" of congenital heart disease patients are children, Jacobs says.

Hospitals With More Deaths Than Expected

Hospital 4-Year Total Patients 4-Year Actual Deaths 4-Year Expected Deaths* Nationwide Medical Center 1348 62 44 Children's Hospital of the King's Daughters 367 16 9 Maine Medical Center 269 12 5

Fourteen hospitals in the STS database were granted the lowest rating, one star. Only three allowed the STS to publish their data. Two of three cared for fewer than 100 congenital heart surgery patients a year, making them low-volume programs. The third reported issues relating to physician performance.

*The number of expected deaths was calculated using the expected mortality rate provided by the STS in relation to the number of observed deaths and the observed mortality rate.

Sources: STS, U.S. News analysis

Twelve patients at the Portland hospital died, five of them after relatively low-risk procedures. Calculations reveal that the center would have been expected to have between four and five deaths during that period. The hospital's overall congenital heart surgery death rate was more than double the expected death rate, according to the STS analysis.

Growing participation in the STS database reflects the increasing acceptance of data-sharing, analysis and transparency as valuable tools for performance improvement. Hospitals that take part supply data on all of their heart operations in newborns, infants, children and adults with congenital heart disease.

"We're constantly looking at our outcomes," Nationwide's Galantowicz says. "I've always believed that data transparency is the key to quality improvement and constantly getting better."

Basken, of the Pediatric Congenital Heart Association, praises the STS approach but says the methodology still isn't perfect.

Results in the two-star category of hospitals, for example, encompass hospitals with such wide variations in performance that it can be tough to make meaningful distinctions among different facilities. "There are two-star hospitals that perform more complex operations than other two-stars," she says. "It puts the burden on the family to do additional research to identify the hospital that's appropriate for the child."

And while death is the ultimate outcome to be avoided, suboptimal care can expose a child to lifelong challenges, Basken says.