In short
A stress test asks whether the heart's blood supply keeps up under demand. The report carries a workload, a symptom record and an electrical verdict, and a positive result is a probability rather than a diagnosis.
Emergency if: Chest pain at rest lasting more than a few minutes, spreading to the arm, neck or jaw, with sweating, nausea or breathlessness — call emergency services now.
On your report
LDL Cholesterol, HDL Cholesterol, Total Cholesterol, Triglycerides +3 more
On this page
01
What the test is asking
At rest, a coronary artery can be substantially narrowed and still deliver enough blood for the heart's needs. Demand is what exposes it. A treadmill test raises the heart's workload in stages while the ECG, blood pressure and symptoms are watched, looking for the point at which supply stops keeping up.
That is a different question from the one an ECG at rest answers, and a different question again from what a coronary calcium score or an angiogram answers. A resting ECG can be entirely normal in someone with significant narrowing, which is exactly why the treadmill exists.
02
Workload, METs and why they matter
The treadmill speeds up and steepens on a fixed schedule, most often the Bruce protocol, and each stage is harder than the last. The report records how long you lasted and the workload reached, usually expressed in METs — multiples of the energy your body uses sitting quietly.
Exercise capacity is one of the strongest pieces of information the test produces, and in many studies it predicts outcome better than the ECG tracing does. Someone who reaches a high workload without symptoms or changes has a genuinely reassuring result, whereas a test stopped early at a low workload is concerning even when the tracing looks unremarkable.
03
ST segment changes: the electrical part
The ST segment is a portion of each heartbeat's tracing that shifts when heart muscle is not getting enough blood. Horizontal or downsloping ST depression appearing during exercise is the classic positive finding, and reports usually state how many millimetres it moved, in which leads, at what workload, and how long it took to settle afterwards.
Changes appearing at a low workload, in many leads, and taking a long time to recover carry more weight than a small shift at peak effort that resolves immediately. Upsloping ST depression is far less specific and frequently means nothing at all.
04
Why the report also records symptoms and blood pressure
Chest tightness that reproduces your usual symptom during exercise and settles with rest carries real weight, even if the tracing is unchanged. Equally, a test in which you felt entirely well at a high workload is meaningful on its own. The report notes why the test was stopped — target heart rate reached, fatigue, symptoms, or a decision by the supervising doctor.
Blood pressure should rise with exercise. A blood pressure that falls as the workload increases is an abnormal and important finding, and is one of the reasons the test is supervised. Reaching the target heart rate matters too: a test stopped before that point is often reported as inconclusive rather than negative, because the demand was never high enough to answer the question.
05
False positives, false negatives
This test produces a substantial number of positive results in people with normal arteries. It is notably less reliable in women, in people whose resting ECG is already abnormal, in those taking digoxin, and where there is left ventricular hypertrophy or a bundle branch block. A positive result in someone at low risk to begin with is therefore quite likely to be a false alarm.
The reverse also happens: a negative test does not exclude coronary disease, particularly if the target workload was not reached. This is why results are interpreted against your background risk rather than read alone, and why a positive test in a low-risk person is often followed by an imaging test rather than straight to an angiogram.
06
What happens next
A clearly negative test at a good workload usually means no further cardiac testing, with attention moving to blood pressure, lipids, blood sugar, weight and smoking. An inconclusive test is often repeated as an imaging stress test — stress echocardiography or nuclear perfusion imaging — which is more accurate and does not depend on the resting ECG being normal.
A strongly positive test, especially at a low workload or with a falling blood pressure, leads to prompt cardiology assessment and often to angiography. Whatever the result, treatment of risk factors continues in parallel; the test measures the problem, it does not treat it.
When to act
Routine — see a doctor
A negative test at a good workload: no further cardiac imaging is usually needed, and attention shifts to blood pressure, lipids, sugar and smoking.
Same-day — call promptly
Chest tightness on exertion that is happening at lower and lower levels of activity, or a positive report you have not yet discussed with a doctor.
Emergency — act now
Chest pain at rest lasting more than a few minutes, spreading to the arm, neck or jaw, with sweating, nausea or breathlessness — call emergency services now.
Values mentioned in this story
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Sources
- Exercise Stress Test — MedlinePlusmedlineplus.gov
- Electrocardiogram (ECG) — NHSnhs.uk
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