St. Christopher's Hospital for Children said Monday that it had stopped conducting elective heart surgeries pending an internal review.

The North Philadelphia facility continues to perform emergency heart surgery, hospital spokeswoman Kate Donaghy said. The hospital did not indicate what prompted the review.

"The hospital's heart surgery and trauma teams remain ready to respond to the needs of emergency patients, including emergency cardiac surgery," Donaghy said in an email.

The news came a year after the hospital declined to participate in a state agency's first-ever evaluation of Pennsylvania hospitals that perform pediatric heart surgeries. St. Christopher's was the only one of the five facilities that declined to share how many of its patients died, though the hospital said then that it would participate in any future evaluations.

The 189-bed hospital is owned by Tenet Healthcare Corp. of Dallas. A CNN investigation last year found an elevated mortality rate at a Florida hospital owned by the same for-profit corporation.

The Florida hospital, St. Mary's Medical Center of West Palm Beach, disputed the CNN findings. But a state panel also had found deficiencies, and in mid-August the hospital shut down its pediatric heart-surgery program and its chief executive officer resigned.

Among the concerns at the Florida facility was the fact that surgeons performed just two dozen of the complex procedures each year.

In recent years, St. Christopher's has done 50 to 60 open-heart surgeries a year that required the heart-bypass machine, according to state health department statistics. By contrast, Children's Hospital of Philadelphia has performed such surgeries on nearly 10 times as many children annually.

As with many types of surgeries, the more pediatric heart procedures a hospital performs, the better the outcomes will be on average, studies have found.

The more-is-better rule applies especially to the most complex procedures, said cardiologist Bradley S. Marino, codirector of research and academic affairs at the heart center at Ann and Robert H. Lurie Children's Hospital of Chicago. These include surgeries performed on newborns whose hearts have backward plumbing or are missing entire chambers. Some babies' hearts, he said, are no larger than a plum.

Though cardiac surgeries have advanced dramatically in recent decades, these procedures are so difficult that survival is by no means a given, especially for the sickest newborns.

"We're not talking about 'take a valve out, put a valve in,' "Marino said. "We're talking Michelangelo-type artwork."

This is not the first time questions have arisen at St. Christopher's. In September 2012, a former employee filed a whistle-blower lawsuit against the hospital. The man, a specialist who operated the heart-lung machine during surgeries, said that from April 2007 through April 2009, 10 heart surgery patients died or suffered neurological complications due to inadequate care. That case is pending.

The attorney who filed that complaint, Bernard Smalley, did not respond to a request for comment Monday.

Smalley also is representing the families of two babies who died after surgery at St. Christopher's - one in June 2011, the other in March 2012.

In the first case, the family contends the baby boy was given too much calcium, leading to cardiac arrest.

In the second case, another family says the child died after multiple mistakes. Following one surgery, nurses failed to warn physicians that the boy's blood pressure was dropping sharply over the course of three hours, and he went into cardiac arrest, the complaint alleges.

The hospital has denied wrongdoing in all three cases.

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@TomAvril1