Introduction
Facing open-heart surgery can be overwhelming, and the numbers doctors share can feel confusing. One of the most common numbers you may hear is your STS risk score. But what does this score really mean? And why is it important?
This article explains the STS risk score in simple terms, so you can understand how it’s used, what low, moderate, and high scores mean, and how it affects decisions about surgery.
What Is the STS Risk Score?
The Society of Thoracic Surgeons (STS) risk score is a medical tool used by heart surgeons to estimate the risk of major complications or death after cardiac surgery. It is based on data from millions of patients across the U.S., making it one of the most reliable ways to predict surgical risk.
Surgeons use it before operations such as:
- Coronary artery bypass grafting (CABG)
- Valve surgery (aortic, mitral, tricuspid)
- Combined procedures (CABG plus valve repair or replacement)
How Is the STS Score Calculated?
The STS score isn’t a single number from one test - it’s calculated from many factors, including:
- Age
- Overall health
- Kidney function
- Lung function
- Heart pumping strength (ejection fraction)
- Presence of diabetes or other medical conditions
- Whether the surgery is urgent or planned
Doctors input these details into the **STS calculator**, which then estimates risk percentages for differentoutcomes.
What Do the STS Score Results Mean?
The score usually gives a percentage risk of death or major complications.
For example:
- Low risk: usually <2% chance of death after surgery
- Moderate risk: about 2–8%
- High risk: >8%
These numbers may sound intimidating, but they are always considered in context. A 2% risk means 98 out of 100 patients do well - an important perspective for patients and families.
Why the STS Score Matters
The STS score helps surgeons and patients:
- Understand the risks of surgery before making a decision
- Compare options, such as surgery vs. less invasive treatments
- Choose the right hospital or surgeon, since higher-risk cases often do better at experienced centers
- Plan recovery by preparing for possible complications
It’s not the only factor surgeons use, but it provides a common language for discussing risk.
Limitations of the STS Score
While powerful, the STS score has limitations:
- It’s based on population averages, not individual biology
- It cannot predict every outcome
- It does not account for personal resilience, support systems, or new surgical techniques
That’s why surgeons always combine the score with their own clinical judgment.
Key Takeaways
- The STS risk score is a trusted tool for predicting surgical risk.
- Scores are classified as low, moderate, or high - each guiding treatment choices.
- The score is one piece of the puzzle, not the entire decision.
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If you’ve been given an STS score and want help understanding what it means for your care, Verus can help. We combine advanced AI tools with expert surgeon oversight to provide clarity and peace of mind.
