When it Comes to Heart Surgery Sometimes Quantity is Quality

by Drew Heyding on March 8, 2012

Recently CNN covered the story of a baby born with heterotaxy syndrome, a rare condition that is often associated with complex congenital heart defects. The baby was treated in a major pediatric medical center in the Midwest. He underwent heart surgery but several months after his birth remained in the intensive care unit in a precarious condition waiting for another surgery.

National Institutes of Health

His mother learned that some hospitals had more experience treating and operating on babies with heterotaxy. Her initial effort to move her son to Children’s Hospital Boston, one of these hospitals, was unsuccessful. As the CNN story explains, Medicaid would not pay for her son to be transferred out of state to a more experienced hospital. Ultimately she was able to bring her son to Boston with the help of social media and the congenital heart disease community. Does it make sense to travel across the country in a situation like this?

Many medical centers in the United States perform congenital heart surgery and great outcomes happen everyday across the country because of the skill and dedication of the medical teams at these hospitals. But some of these hospitals have higher surgical volumes (meaning they perform more operations than the others). And new research in the journal Pediatrics supports prior studies that have shown that these high volume medical centers give some children with heart defects a better chance of survival.

As far back as the 1970s studies had begun to identify a link between higher mortality (more deaths) and low surgical volume (less experience with a particular operation). This early research focused on adult surgeries. More recently, studies have looked at surgical mortality rates among children.  Much of this research has explored the impact of surgical volume on mortality rates among children operated on for congenital heart disease.

Some studies have focused on specific operations that are especially complicated. Children born with a type of heart defect called hypoplastic left heart syndrome require several surgeries done in sequence. The first operation is called the Norwood procedure.  One study in 2005 and another in 2008 found that survival rates after this procedure were higher in hospitals that performed the operation more often.

Other studies have looked at overall pediatric cardiac surgery mortality data. A study in 2009 used a national database to explore the link between volume and mortality more closely. This research made sure to take into account any imbalance in patient-level risk factors (how sick the children were before their operations) and surgical case mix (how many straightforward versus complex surgeries a hospital did).  These adjustments helped ensure that the comparisons among different hospitals were valid. The researchers concluded that when an operation was especially complex, more children survived the surgery if the child was treated in a high volume hospital.

The newest study published last month in Pediatrics uses more recent data from the same national database. The authors were interested in better understanding the reasons why low surgical volume is linked with higher mortality in congenital heart surgery. The study used data from 2006 to 2009 that included a total of 35,776 patients.

The lowest volume hospitals were defined as centers that operated on less than 150 heart defect cases per year. The highest volume centers operated on more than 350.  Surgeries were classified based on an established risk stratification system (where 1 represents the operation with the lowest risk of death and 5 the highest). Patient characteristics were collected including information on any individual risk factors present before the operation.

Data analysis showed that children who underwent a high risk surgery (category 4 or 5) had higher death rates at a low volume center. The odds of dying in the lowest volume center were 1.86 times higher than the odds of dying in the highest volume center. (There was no difference in mortality rates related to surgical volume when the surgery was low or medium risk).

Low volume hospitals did not have more complications than high volume hospitals. Complication rates may be unrelated to surgical volume because they are tied directly to patient related risk factors. (For example, an infant with lung and kidney problems in addition to a heart defect is more likely to develop a complication than an infant who has no other organ involvement besides the heart regardless of where they have surgery.)

But patients who did have a complication were more likely to die if they were in a low volume hospital than a high volume hospital. (This phenomenon has been observed in research on adult surgery outcomes and termed “failure to rescue”.) A hospital that performs more heart surgeries will gain more experience. Their medical teams will recognize complications more promptly and treat them more effectively because of this experience.

This new research supports health policy that would promote regionalization of specialized surgical services. (Meaning certain hospitals would be designated to care for babies who require surgery for complex heart defects like those associated with heterotaxy and hypoplastic left heart syndromes).

Right now parents often have different hospitals to choose from. Because the closest option may not always be the best, parents of infants and children who will require high risk congenital heart surgery should be informed of the connection between high surgical volume and survival rates.