Treadmill Stress Test (TMT)

A Treadmill Stress Test records a continuous 12-lead ECG while you walk on a treadmill at progressively increasing speed and incline (Modified Bruce Protocol). The purpose is to detect ECG changes indicating reduced blood flow to the heart (ischaemia) during exercise — which is not visible on a resting ECG in many patients with coronary artery disease. It also measures exercise capacity (METs), heart rate response, and blood pressure response. The result includes a Duke Treadmill Score for risk stratification.

A positive TMT shows evidence of cardiac ischaemia (reduced blood flow) during exercise. The main positive finding is ≥1 mm horizontal or downsloping ST depression in two or more leads during exercise. Other positive findings include chest pain during the test, exercise-induced fall in blood pressure, or significant arrhythmia. A positive TMT does not confirm coronary artery disease with certainty — it indicates probability of significant stenosis, typically requiring further evaluation with coronary CT angiography or invasive coronary angiography.

The Duke Treadmill Score (DTS) is a validated risk score combining exercise duration (minutes), maximum ST deviation (mm), and angina index (0=none, 1=non-limiting, 2=test-stopping). DTS = time − (5 × ST deviation) − (4 × angina index). Score ≥+5 = low risk (annual mortality <1%); −10 to +4 = intermediate risk; ≤−11 = high risk (5-year mortality >5%). At Heartwise Cardiology, the DTS is calculated on every TMT report to guide management decisions.

Eat a light meal 2 hours before the test (do not come fasting). Wear comfortable walking shoes and loose clothing. Continue all medications unless specifically told to stop beta-blockers. Avoid caffeine and smoking for 3 hours before. Do not apply body lotion or powder to your chest. Inform your cardiologist of any recent chest pain or new symptoms before the test begins. Bring previous TMT reports and medication list.

TMT is contraindicated in: unstable angina (rest or worsening chest pain), acute MI in the past 2–5 days, uncontrolled heart failure, severe aortic stenosis, resting BP >200/110 mmHg, active myocarditis or pericarditis, and significant resting arrhythmia. For patients who cannot walk on a treadmill (orthopaedic or neurological limitation), alternative stress testing — pharmacological dobutamine stress echo, nuclear perfusion imaging, or CT coronary angiography — can be arranged.

If you are unable to complete the full Bruce protocol due to exhaustion, breathlessness, leg fatigue, or other symptoms, the test is still clinically useful. The key metrics recorded — exercise duration in minutes (or METs achieved), maximum ST deviation, and reason for stopping — are all components of the Duke Treadmill Score. Achieving <5 METs (approximately Stage 1) is an independent predictor of increased cardiovascular risk. Your cardiologist will interpret the result in context, and if the test was limited by non-cardiac reasons, alternative stress testing options can be considered.

The exercise ECG has a sensitivity of approximately 68% and specificity of approximately 77% for detecting significant coronary artery disease (>70% stenosis). This means it is moderately accurate but not perfect — false positives (abnormal TMT with normal coronary arteries) and false negatives (normal TMT despite significant CAD) do occur. Accuracy is higher in patients with multi-vessel disease and lower in single-vessel disease. TMT is best used as a risk stratification tool rather than a definitive diagnostic test — an abnormal result indicates intermediate-to-high probability of CAD and guides the need for further imaging.

A TMT records only the ECG during exercise, detecting electrical signs of ischaemia (ST changes). A stress echocardiogram (stress echo) adds ultrasound imaging of the heart before and immediately after exercise, looking for new wall motion abnormalities that indicate ischaemia. Stress echo is significantly more sensitive (approximately 80–85%) and specific (approximately 84–86%) than TMT alone, and can localise the ischaemic territory to a specific coronary artery. However, stress echo requires additional equipment, expertise, and is more expensive. TMT remains the recommended first-line test for intermediate-risk patients with suspected CAD due to its availability, simplicity, and cost-effectiveness.

This depends on the purpose of the test. If the TMT is being performed to diagnose coronary artery disease (diagnostic test), your cardiologist may ask you to stop beta-blockers and rate-limiting calcium channel blockers for 24–48 hours before the test, as these drugs can mask ischaemic changes and prevent you from reaching target heart rate. However, if the test is to assess the effectiveness of your current treatment regimen (on-therapy assessment), continue all medications as usual. Never stop any medication without explicit instruction from your prescribing cardiologist. Bring a complete list of your medications to the appointment.