Children's Hospital Colorado
Heart institute
Heart institute

Pediatric Cardiac Surgery Outcomes



Hearing that your child needs heart surgery can be overwhelming. In the Heart Institute at Children’s Hospital Colorado, our caregivers understand the anxiety and stress that can come with a serious diagnosis. We’re here to guide you throughout your child’s care, from diagnosis to treatment and beyond.

In our history, we’ve cared for thousands of infants, children, teens and even adults with a vast variety of congenital heart defects (CHDs). As the largest pediatric heart surgery program in the region, we perform more than 500 heart surgeries per year. Our highly specialized providers take on the most complex heart problems and achieve some of the best outcomes in the nation.

It’s all in support of the measure that matters most: the long and productive lives our patients go on to lead.

What are pediatric cardiac surgery outcomes?

In the medical world, the term “outcomes” means “success rates.” Many – but not all – pediatric cardiology centers measure and report their surgical outcomes to help parents make the best decision about where to take their child for heart surgery.

Here, we evaluate our success by monitoring and comparing our cardiac surgery statistics with other top pediatric hospitals. We also routinely check and publish other quality and patient safety metrics and heart transplant outcomes to ensure that families have the latest information when deciding who should care for their child.

Why transparency matters

We believe that families have the right to know every heart surgery program’s outcomes. Our Heart Institute is the only pediatric heart surgery program in Colorado and one of the few in our region to publicly report our cardiac surgery outcomes data. This transparency is one of the keys to our success as one of the best hospitals for congenital heart surgery in the country.

When researching heart surgery programs, parents should look for multiple outcome measures, such as total survival, survival by surgical complexity and length of stay, and consider these statistics together. No single metric should stand alone.

View some of the many things we measure and see our latest outcomes data below.

Open heart surgery survival rates

Heart surgery programs typically report their overall survival rate as well as survival rates based on the complexity of the surgery.

What we measure:

The percentage of heart surgery patients who survive their open heart surgery.

At Children’s Colorado, our overall survival rate for all cardiac surgery patients, regardless of how complex the surgeries are, is 97.3%. The national average is 97.2%.

97.3% Cardiac surgery survival rate at Children's Colorado

Source: STS Jan. 2015 through Dec. 2018

What it means:

Having a higher survival rate indicates that a pediatric heart center is more experienced and better equipped for congenital heart surgery, and that fewer patients pass away during or after surgery. Here at Children’s Colorado, our survival rate is slightly higher than the average.

Some heart centers take more complicated cases than others, which is why it’s important to also compare survival rates by complexity and type of defect.

Cardiac surgery survival rates by complexity

Some congenital heart defects are more complex than others. And because there are so many types of heart defects, no pediatric heart program will see the exact same defects each year. The Society of Thoracic Surgeons (STS), the organization with the largest congenital heart surgery database, organizes the types of surgeries into five categories, which are referred to as “STAT categories” so they are easier to compare.

What are STAT categories?

STAT categories classify heart surgeries into groups based on how risky or complex they are. The STAT 1 category indicates surgeries with the lowest risk of death, while the STAT 5 category indicates the surgeries with the highest risk of death. A hospital that has a high survival rate for STAT 5 cases indicates success at handling unpredictable situations during the operation and in recovery.

What we measure:

STAT 5 neonatal survival measures the percentage of babies with the most complex heart defects who survive their surgery and have been discharged from the hospital.

Graph comparing overall STAT 5 newborn survival (the most complex cases) at Children’s Colorado and nationally. Higher is better: Children’s Colorado = 89.8%; National = 84.7%; Data from Jan. 2015 through Dec. 2018

What it means:

At Children’s Colorado, our surgical team specializes in some of the most complex cardiovascular procedures, with special expertise in surgical repair during the newborn period. Having a high STAT 5 survival rate means that the newborn babies we treat are more likely to survive their operation than the national average, even though we accept many more complex patients.

Pediatric cardiac surgery mortality

Open heart surgeries can be risky, and some deaths and complications are inevitable. Looking at the data another way, surgery programs also report mortality, which is the percentage of patients who did not survive their operation. (The more complex the surgery, the higher the risk of mortality.) It’s important to compare the mortality rate by patient age, type of operation and STAT category because these rates can vary from the program’s overall mortality rate.

Newborn cardiac surgery mortality

Performing heart surgery on newborn babies is more challenging due to the young age and small size of the patients. By comparing newborn mortality rates along with STAT category, parents can get an idea of how well the surgeons perform in the most challenging cases.

What we measure:

We compare our mortality rates for newborn patients with national averages by the complexity of the surgery.

Graph comparing cardiac surgery mortality rates by STAT category at Children’s Colorado and nationally. Lower is better: STAT 1 Children’s Colorado = 0.0% (n=5), National = 2.4%; STAT 2 Children’s Colorado = 3.1% (n=64), National = 3.5%; STAT 3 Children’s Colorado = 2.9% (n=35), National = 2.8%; STAT 4 Children’s Colorado = 8.0% (n=150), National = 8.4%; STAT 5 Children’s Colorado = 10.2% (n=88), National = 15.3%. Data from Jan. 2015 through Dec. 2018

What it means:

At Children’s Colorado, our surgeons have extensive experience correcting heart defects in even the youngest patients— some just a few hours old. Overall, our mortality rates for newborns are lower than the national average, including in more complex cases. Our mortality rate for STAT 3 cases was 0.1% higher than the national average during this reporting period.

Cardiac surgery mortality by procedure

Cardiac surgery programs can also report mortality rates by the specific operation. These are called “benchmark operations,” and they are one way surgical centers can compare outcomes. Note that these data do not take into account a patient’s specific risk factors prior to surgery.

In the table below, we report the total number of benchmark operations at Children’s Colorado, as well as the mortality rates here compared to the national average.

What we measure:

Index case mortality shows the percentage of patients who received a specific operation and did not survive the surgery or who died within 30 days of their operation.

Index case mortality, Jan. 2015 through Dec. 2018

Operation Total operations Children's Colorado Children's Colorado mortality
Lower is better
National mortality (STS)
Lower is better
Arterial switch repair 24 0% 2.0%
Arterial switch repair + Ventricular septal defect 11 0% 5.1%
Atrioventricular canal defect repair 43 2.3% 2.1%
Glenn / Hemi-fontan 82 1.2% 2.0%
Fontan procedure 74 0% 1.0%
Norwood procedure 74 9.5% 14.4%
Tetralogy of Fallot repair 36 2.8% 1.2%
Truncus 7 0% 8.9%
Ventricular septal defect repair 126 0.8% 0.5%
Off bypass coarctation of the aorta 118 0.8% 1.3%

What it means:

For the vast majority of the open heart surgeries listed above, our mortality rates are lower than the national average. For a few procedure types (atrioventricular canal defect repair, tetralogy of Fallot repair and ventricular septal defect repair), our rates were slightly higher than the national average for this time period.

It can also be challenging to compare outcomes by procedure alone. Factors such as patient age, other health conditions (called comorbidities) and genetic conditions can make procedures riskier. This is why pediatric heart surgery programs should report a wide range of outcomes, including how well patients do when they are at higher risk.

Risk-adjusted cardiac surgery mortality rates

To help compare programs, the STS reports what are called “risk-adjusted” mortality rates, or the “adjusted” mortality rate (AMR). The AMR is a statistical evaluation developed by STS that predicts a patient’s risk of undergoing surgery. This evaluation attempts to include patient-related risk factors prior to surgery, such as age, weight and genetic abnormalities, in addition to the patient’s surgical risk. Using this method, STS compares the actual patient outcomes (observed outcomes) to expected outcomes (those predicted by the statistical model). Ultimately, a heart center should strive to have observed mortality that is the same or less than the expected mortality.

The AMR also helps evaluate if hospitals are losing patients that they did not expect to die. Many experts say it is a strong indicator of a hospital’s performance.

Adjusted mortality rate (AMR) by age group

What we measure:

We track the observed and expected mortality rates by patient age groups, beginning with newborns and adding infants, children and adults.

  • Observed mortality rate is the number of deaths divided by the total number of eligible surgeries.
  • Expected mortality rate predicts how many deaths we would expect when taking into account the severity or complexity of cases we treat.

Observed vs. expected mortality and AMR by group, Jan. 2015 through Dec. 2018

Age category Total patients Observed mortality rate Children's Colorado
Lower is better
Expected mortality rate Children's Colorado
Lower is better
Children's Colorado AMR (95% confidence interval)
Lower is better
National adjusted rates (STS)
Lower is better
Newborns 342 7.0% 7.1% 7.9% [5.1,11.6] 8.1%
Newborns + Infants 826 4.7% 4.7% 4.7% [3.3,6.3] 4.6%
Newborns + Infants + Children 1485 3.0% 3.0% 2.9% [2.1,3.9] 3.0%
Newborns + Infants + Children + Adults (All Patients) 1671 2.7% 2.8% 2.7% [2.0,3.6] 2.8%

What it means:

At Children’s Colorado, our observed mortality rates by group are the same or lower than what was expected of our specific patient population. When comparing our AMR to the overall national AMR, we are also lower than the national average in three out of four groups. For the newborns and infants group, our AMR is 0.1% higher than the national AMR, a very small difference.

AMR by STAT category

What we measure:

We also compare the observed and expected mortality rates overall and by complexity. Comparing the program’s observed mortality rate with the expected mortality rate tells you whether a program’s surgeries went as well as planned. When the observed mortality rate is equal to or lower than the expected mortality rate, it indicates that the surgical program is providing optimal care for pediatric heart patients.

Graph comparing observed cardiac surgery mortality rates with expected cardiac surgery mortality rates at Children’s Colorado and nationally. Grouped by STAT category. Lower is better. All STAT: Children’s Colorado n=1671, Children’s Colorado observed =2.7%, Children’s Colorado expected = 2.8%, Nationally = 2.8%; STAT 1: Children’s Colorado n=560, Children’s Colorado observed =0.4%, Children’s Colorado expected = 0.4%, Nationally = 0.4%; STAT 2: Children’s Colorado n=504, Children’s Colorado observed =2.0%, Children’s Colorado expected = 1.7%, Nationally = 1.5%; STAT 3: Children’s Colorado n=167, Children’s Colorado observed =1.8%, Children’s Colorado expected = 1.9%, Nationally = 2.1%; STAT 4: Children’s Colorado n=344, Children’s Colorado observed =5.5%, Children’s Colorado expected = 6.2%, Nationally = 6.4%; STAT 5: Children’s Colorado n=96, Children’s Colorado observed =11.5%, Children’s Colorado expected = 12.1%, Nationally = 14.0%. Data from Jan. 2015 through Dec. 2018

What it means:

When examining the observed vs. expected mortality for all surgeries, Children’s Colorado performs slightly better than expected and slightly better than the national average. For high risk surgeries, we perform consistently better than the expected outcome and the national average. We did see an increase in our mortality in STAT 2 surgeries, that although not statistically significant, have helped us determine where we can ensure improved care for these patients.

Average length of stay

By comparing the average length of stay between hospitals, parents can learn which programs are best equipped to care for their child. The longer a child stays in the hospital after surgery, the more likely they are to have complications.

What we measure:

The chart below shows the average number of days that children stay in the hospital for heart surgery by STAT category.

Graph comparing length of stay by STAT category in days at Children’s Colorado and nationally. Lower is better. STAT 1: Children’s Colorado = 6.2 (n=560), National = 7.5; STAT 2: Children’s Colorado = 17.1 (n=17.1), National = 20.8; STAT 3: Children’s Colorado = 13.5 (n=13.5), National = 16.0; STAT 4: Children’s Colorado = 25.7 (n=344), National = 28.3; STAT 5: Children’s Colorado = 44.9 (n=96), National = 48.0. Data from Jan. 2015 through Dec. 2018

What it means:

Cardiac surgery patients at Children’s Colorado spend less time in the hospital than the national average, indicating that they receive high quality care before, during and after surgery that helps them go home sooner.

Pediatric heart surgery volumes

Finally, when it comes to congenital heart surgery, volume matters. Studies show that kids who need heart surgery do better when they are treated by medical teams that perform a high number (or volume) of surgeries. This is because surgeons in high volume centers get more experience and see a wider range of heart defects than surgeons who perform only a handful of surgeries per year.

Performing hundreds of surgeries each year indicates that the hospital is a high volume center and is likely to have better patient outcomes. This is particularly true for patients with complex heart defects.

Number of heart surgeries performed at Children’s Colorado

What we measure:

Surgical volume indicates the number of heart surgeries performed at a hospital.

Cardiopulmonary bypass indicates when a patient has to be connected to a machine that does the work of the heart and lungs while surgeons repair the heart. These surgeries are more complex than those without cardiopulmonary bypass.

Surgical volume

Operation type 2015 2016 2017 2018
Cardio-pulmonary bypass 363 355 338 326
No cardio-pulmonary bypass 136 136 119 121
Other 55 66 56 69
Total 554 557 513 516

What it means:

Children’s Colorado is a high-volume cardiac surgery center, performing more than 500 pediatric heart surgeries each year. We also perform hundreds of surgeries with cardiopulmonary bypass each year. This means we have the team, the experience and the facilities to treat kids with a wide variety of heart defects.

Where does this data come from?

This data is from the Society of Thoracic Surgeons (STS) Congenital Heart Surgery Database, the largest congenital heart surgery database in the world. It includes data from more than 100 North American pediatric heart surgery programs. This database allows us to compare our outcomes to other heart surgery centers across the country and continent.

If a center does not report to a national data program or does not share their outcomes publicly, you should ask why.

How often is STS data updated?

Children’s Colorado and other centers submit data to the STS twice per year. The STS then verifies the data and generates reports that allow us to compare results with peers.

We publish our outcomes data on this website as soon as possible following the STS data release, also twice per year.

How does STS define surgical survival?

STS defines surgical survival as the percentage of heart surgery patients that are discharged alive and, if discharged within 30 days after surgery, whether they are alive at home. The STS updates its database every six months, and reports the national average from this data.

How does STS define surgical mortality?

STS defines surgical mortality as the percentage of heart surgery patients who pass away during their operation or, if they have been discharged, within 30 days of their surgery. Mortality also includes the patients who are not discharged within 30 days but pass away during their hospitalization.

Using STS definitions ensures that institutions across the country are using consistent data reporting methods.

From the operating room to the cath lab

At Children’s Colorado, we’re repairing more congenital heart defects using lower-risk cardiac catheterization instead of open heart surgery.

See how

Learn even more about quality and patient safety standards and our heart transplant outcomes at the Heart Institute.

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