How We Rate Heart Surgery Groups

(See our technical report for a more detailed description of the methods used to determine the ratings.)

Over 90 percent of cardiac surgery groups in the U.S. voluntarily submit their performance data to the STS Adult Cardiac Surgery Database. The ratings on the Consumer Reports website include only those groups that have agreed to let us publish their performance results. We will periodically update the ratings with more current data as well as data from additional groups that agree to release their information to us.

Many surgical groups that have not yet agreed to share their data with Consumer Reports do participate in the STS database. So you can ask a group whether it is involved with STS and, if so, ask about its results on the STS performance measures. Practices not involved with STS often report to similar state-run databases, so you can ask about those, too. Notably, New York heart bypass surgeons often participate only with their state database. If a group refuses to provide you with the information you need, or can't provide it, our medical experts say it's best to look elsewhere for medical care.

The STS has currently agreed to release to us only the group information for several reasons. Pooling results from all the surgeons in each group provides more data, allowing for more statistically robust results. Individual surgeons within a group sometimes specialize in difficult cases while others work on simpler ones; combining data gives a more even view of their performance. Bypass surgery also depends on the performance of a team before, during, and after the operation, so group performance might be a better indicator of quality than individual performance. Finally, focusing on the entire group makes it easier to track the results over time, even if individual surgeons move or retire. When available, we do provide the names of the surgeons who are currently members of each group, so you can ask specific ones about their track record.

The ratings reflect results from stand-alone, or isolated, heart-bypass operations called coronary artery bypass grafting (CABG). In the standard version of the operation, a surgeon opens the chest, reroutes blood through a heart-lung machine, stops the heart, grafts arteries or veins around the blockages, restarts the heart, and then wires the chest back together. The ratings can also include results on newer versions of that operation, such as off-pump bypass (in which surgeons immobilize just the part of the heart receiving the graft); minimally invasive bypass (in which they operate through a small incision and several puncture sites); or a hybrid procedure (in which a surgeon does a minimally invasive bypass on the major coronary arteries, and then an interventional cardiologist clears blockages in other arteries using angioplasty and stents). But the ratings don't include bypass operations that are combined with other major cardiac procedures, such as valve replacement.

STS uses 11 standardized measures endorsed by the National Quality Forum, a nonprofit organization dedicated to establishing national health-care standards for performance improvement. Those measures fall into four broad categories. Two of them—recommended medications and optimal surgical technique—reflect how well surgeons adhere to the best established practices. The other two—patient survival and the absence of surgical complications—reflect how their patients fare.

• Patient survival. This is based on the chance that a patient will survive at least 30 days after the surgery and will be discharged from the hospital.
• Absence of surgical complications. This is based on the chance that a patient will not experience any of these five serious complications of heart bypass surgery during their hospitalization: extended breathing support on a ventilator, an infection in the breastbone incision, kidney failure, a stroke, or a repeat operation for postoperative bleeding or other causes.
• Recommended medications. This is based on the chance that a patient will get all of the following drugs: a beta-blocker before the procedure and aspirin, a beta-blocker, and a statin or other medication to lower LDL (bad) cholesterol afterward.
• Optimal surgical technique. This is based on the chance that a patient will receive at least one graft involving an internal mammary artery, which improve long-term survival compared with grafts taken from veins.

For each of the four measures, STS compares a group's performance with the average performance of all the groups in the database. For survival and complications, the results are adjusted for the overall health of a group's patients, since some surgical groups treat older or sicker patients than others. (That adjustment is not necessary for medications and surgical technique, however, since the right drugs and best surgical approaches should be used with all eligible patients, regardless of their health.)

The overall heart bypass rating combines the scores from those four measures. For each individual performance measure, as well as the overall rating, groups that score significantly above average get three stars, average performers get two stars, and those that score significantly below average get one star. Since the average performance of surgical groups has increased substantially in the past two decades, it's possible to get very good care even from many two-star groups.

Look at the surgical group's rating on each individual measure, identify the particular areas of concern, and discuss them with your surgeon. For example, if the group received one star in prescribing recommended drugs or using the proper surgical technique, ask that the surgeons take extra care on those issues when treating you.

Research has found that a group's performance depends far more on how well it adheres to established best practices than how many procedures it does each year. So volume is not one of the measures used by STS to rate groups. However, surgical volume is important for statistical reasons. Specifically, groups that do a relatively small number of heart bypass surgeries are statistically harder to differentiate from average, so these groups are more likely to get an average, or two-star, rating simply because there is less information about them.

• The ratings are currently limited to groups that voluntarily agree to participate in the STS database, and then agree to release the data to us.
• The ratings do not include results from individual surgeons, only surgical groups.
• Even though survival and complications are statistically adjusted for how sick a group's patients are, there are other factors that might have an impact on the differences between groups. That, together with other statistical issues, might sometimes make it difficult to compare surgical groups directly.
• While these ratings are based on the most comprehensive set of data in the world regarding heart bypass surgery, some important quality measures might not be included in the STS ratings.
• Some of the measures are difficult to define precisely, so differences might exist in how groups collect and report their data.
• The percentages reported are not exact numbers but estimates based on the statistical model used, and have some a margin of error.
• Practices that do a relatively small number of isolated heart bypass operations are statistically harder to differentiate from average than groups that do a larger number of them. So groups with fewer operations are more likely to get an average, or two-star, rating.
• In some cases, a surgeon is part of more than one group, and the two (or more) groups might have different scores. These scores might differ because of the different patients treated at each of the groups, because of the mix of surgeons whose performance is reported together at each group, or because of other factors affecting the team performance of a group of surgeons.