Duke Score - Treadmill Score for CAD Risk

The duke score calculator is a clinical tool that turns a standard Bruce protocol treadmill test into a single weighted index for suspected coronary artery disease. It uses Bruce protocol exercise time, maximum net ST-segment deviation, and a treadmill angina index to estimate CAD risk and 4-year survival.

• • Outpatient chest pain workup: Cardiology teams enter the three stress-test numbers to see whether the patient falls into the low, medium, or high CAD risk band before ordering more imaging.
• • Preoperative cardiac risk review: Pre-op clinics use the index with functional capacity notes to flag patients who may need cardiology clearance before non-cardiac surgery.
• • Cardiac rehabilitation intake: Rehab programs record the result at intake and during follow-up stress tests to document how the risk picture is changing.

The index was developed at Duke University and validated in a 613-patient outpatient cohort published in 1991. The same three-component formula is still the standard summary of a Bruce protocol stress test in adult cardiology.

The result is a signed integer that ranges from about -25 (highest CAD risk) to about +15 (lowest). The cutoffs are 5 or higher for low risk, -10 to +4 for medium risk, and below -10 for high risk, with 4-year survival of 99%, 95%, and 79% in the original cohort.

When the stress-test report also flags a resting or recovery heart rate worth tracking, the ECG Heart Rate Calculator helps document both numbers in the same chart.

The calculator multiplies two of the three stress-test readings by fixed weights and subtracts them from the Bruce protocol exercise time. The result maps to a published CAD risk band and 4-year survival reference.

• Exercise time: Total treadmill time in minutes on the standard Bruce protocol. Longer time is a positive contributor.
• ST-segment deviation: Maximum net ST depression or elevation in millimeters in any lead except aVR. Larger deviations are weighted negatively.
• Treadmill angina index: 0 = no angina, 1 = non-limiting typical angina, 2 = exercise-limiting angina that stopped the test.

The weighting reflects what the original cohort showed: a one-minute change in Bruce time shifts the score by one point, a one-millimeter change in ST deviation shifts the score by five points, and any angina shifts the score by at least four. ST deviation is the most influential input.

The index is a straight linear combination, so the calculator does not need lookup tables or sex-specific cutoffs. The risk bands and 4-year survival reference come from the same 1991 paper.

According to Mark DB et al. - N Engl J Med 1991, treadmill score formula and 4-year survival bands from the 613-patient outpatient cohort

Because the result depends on how long the patient stays on the treadmill, the Target Heart Rate Calculator shows the heart-rate zones that explain a short Bruce time versus a long one.

Each input carries its own weight in the formula. Understanding what each measurement captures makes the result easier to interpret alongside the rest of the stress-test report.

The three inputs do not always agree. A patient with little ST change but limiting angina can still land in the medium or high band because the angina component pulls the score down. A patient with a long Bruce time and a small ST change often lands in the low band because the time component offsets the ST penalty.

Because the index is one piece of a broader coronary risk picture, the LDL Calculator adds the LDL cholesterol context that often accompanies a stress-test referral.

Pull the three numbers from the Bruce protocol stress-test report, enter them in the form, and read the result against the published risk bands and 4-year survival reference.

1. 1 Enter Bruce protocol exercise time: Type the total treadmill time in minutes from the stress-test report, using one decimal place if the report gives it that way.
2. 2 Enter maximum net ST-segment deviation: Type the largest net ST depression or elevation in millimeters in any lead except aVR. Most reports list it next to the ST trend graph.
3. 3 Pick the treadmill angina index: Choose 0 for no angina, 1 for non-limiting typical angina, and 2 for exercise-limiting angina that stopped the test.
4. 4 Read the result: The primary output is the signed integer index. A value of 5 or higher is low risk, -10 to +4 is medium risk, and below -10 is high risk.
5. 5 Review the 4-year survival reference: The calculator shows the 4-year survival reference for the risk band, which helps frame what the index means for prognosis and follow-up.
6. 6 Reset to clinical defaults: Use the reset button to return to a clean starting state for a new patient's three readings.

A 54-year-old man completes a Bruce protocol test in 6 minutes, has 1.0 mm of ST depression in lead V5, and reports non-limiting chest tightness. The nurse enters 6, 1.0, and 1. The result reads -3, the CAD risk band reads Medium risk, and 4-year survival shows 95 percent. The team uses the medium-risk flag to order further non-invasive imaging before deciding on catheterization.

If the same patient also reports leg pain during exertion, the ABI Calculator gives a quick read on peripheral arterial disease that fits the same referral pattern.

Turning three stress-test numbers into a single weighted score gives the cardiology team a shared language, a documented prognosis anchor, and a cleaner decision point for the next step.

• • A documented prognosis anchor: The 4-year survival reference for the risk band travels with the chart and is easier to compare across visits than a paragraph of stress-test findings.
• • A shared decision threshold: A score of -11 or lower is a clear signal to discuss catheterization, while 5 or higher usually supports medical therapy and risk-factor control without invasive testing.
• • A single weighted number: The three inputs are weighted differently, so the score captures the dominant signal without losing the smaller contributors.
• • A repeatable record for review: Documented results support chart audits, risk-stratified follow-up, and quality improvement work in chest-pain clinics and pre-op programs.
• • A teaching tool: The three-component framework helps orient new cardiology fellows, primary care clinicians, and exercise physiologists to how a Bruce protocol report is read.
• • A complement to other risk tools: The index fits naturally alongside lipid panels, blood pressure readings, and imaging decisions.

The score is most useful when the same three inputs are recorded for every stress test in a clinic. A running series of results usually tells a clearer CAD risk story than a single value.

The result is a piece of the larger cardiovascular risk picture, and the Cholesterol Ratio Calculator provides the lipid numbers that often travel with a stress-test referral.

The result is sensitive to how the stress test is performed, how the ST change is measured, and what counts as angina. A few recurring factors move the score more than others.

• • The index is a prognostic tool, not a stand-alone diagnostic test. A low score does not rule out coronary disease and a high score does not rule it in, and further imaging or catheterization is often needed to confirm CAD.
• • The 4-year survival reference comes from the 1991 outpatient cohort. Modern cohorts on contemporary medical therapy may have different absolute numbers, so the percentage is a planning anchor.
• • The score was validated in adults able to exercise on a treadmill. Patients with left bundle branch block, paced rhythm, or recent revascularization need different risk tools.

The same caveats that apply to any single risk index apply here: the result is most useful when it is read alongside symptoms, resting ECG findings, imaging, and the rest of the cardiovascular risk picture, and a borderline medium-risk result often pushes the team toward further non-invasive imaging rather than immediate catheterization.

According to Gibbons RJ et al. - ACC/AHA 2002 Exercise Testing Guideline (Circulation), the 2002 ACC/AHA guideline on exercise testing endorses the Duke treadmill score as a validated prognostic tool that combines Bruce protocol exercise time, maximum ST-segment deviation, and an angina index to classify patients as low, intermediate, or high risk.

Both this index and ICU-style severity scores rely on a small, structured set of clinical inputs, and the Apache II Calculator shows the same pattern of risk stratification in a different care setting.