Stress Test — Purpose, Procedure & Normal Values | MyMedicPlus

A cardiac stress test — also called an exercise stress test, exercise tolerance test (ETT), or treadmill test — evaluates how the heart performs under the physiological demand of controlled physical exertion. During exercise, oxygen demand from the myocardium increases substantially; if coronary arteries are significantly narrowed by atherosclerotic plaques (coronary artery disease, CAD), the increased demand cannot be met, producing ischaemia that manifests as characteristic changes on the ECG, symptoms, or both. The most common form is a treadmill exercise ECG, in which the patient walks on a treadmill with progressive increases in speed and incline following the Bruce protocol while a continuous 12-lead ECG, heart rate, blood pressure, and oxygen saturation are monitored. Patients unable to exercise adequately due to orthopaedic limitations, severe deconditioning, or peripheral vascular disease may instead undergo a pharmacological stress test using dobutamine (a synthetic catecholamine that increases heart rate and contractility) or adenosine/regadenoson (coronary vasodilators), combined with echocardiography (stress echo) or nuclear myocardial perfusion scintigraphy to assess myocardial viability, wall motion, and perfusion.

A cardiac stress test is ordered for several specific clinical indications. To investigate chest pain on exertion (stable angina or atypical chest pain) and to determine whether the symptoms are cardiac in origin. To detect suspected coronary artery disease (CAD) by provoking ischaemic ECG changes or wall motion abnormalities in a controlled, supervised setting. To evaluate exercise capacity and functional status before cardiac rehabilitation programmes, before major non-cardiac surgery, or before patients return to strenuous occupational or recreational activities after a cardiac event. To assess prognosis after a myocardial infarction (heart attack) — a submaximal or symptom-limited stress test at 5–7 days or a full exercise test at 3–6 weeks post-infarction stratifies risk. To investigate and provoke exercise-induced arrhythmias — palpitations, syncope, or pre-syncope occurring specifically with physical activity. To evaluate chronotropic response (heart rate reserve) and assess the effectiveness of rate-controlling medications (beta-blockers, calcium channel blockers) in treated CAD or arrhythmia. To assess for exercise-induced bronchospasm in athletes when asthma is suspected.

Eat a light meal or snack 2–3 hours before the test appointment, but do not eat or drink anything except water in the 2 hours immediately before the test, as a full stomach during vigorous exercise can cause nausea and vomiting and may affect ECG baselines. Avoid caffeine in all forms — coffee, tea, energy drinks, cola, and chocolate — for 12–24 hours before the test, as caffeine masks the chronotropic effects of adenosine (if pharmacological stress testing is planned) and artificially elevates the resting heart rate. Wear comfortable, properly fitting athletic shoes with good ankle support and loose, breathable exercise clothing, as you will be asked to walk or run on a treadmill. Your cardiologist will give specific instructions about whether to hold or continue cardiac medications. Beta-blockers and rate-limiting calcium channel blockers (verapamil, diltiazem) are generally held for 24–48 hours before a diagnostic stress test (to diagnose new CAD), as they blunt the heart rate response and reduce sensitivity; they are continued if the test is for prognosis monitoring or assessment in treated CAD. Continue all antianginal nitrates unless specifically instructed otherwise. Bring a list of all current medications to the appointment.

On arrival, you change into a hospital gown. A cardiac physiologist or technician shaves and cleans small areas of your chest skin with an abrasive pad and alcohol wipe. Ten adhesive ECG electrode patches are placed on the chest and limbs to record a continuous 12-lead ECG. A blood pressure cuff is placed on one arm for automated measurements every 2–3 minutes. A resting ECG and resting blood pressure are recorded as baseline. You step onto the treadmill, which begins moving slowly at an incline of 10 degrees (Bruce protocol Stage 1: 2.74 km/h, 10% grade). Every 3 minutes the speed and gradient increase through up to 7 progressive stages. The cardiologist or physiologist monitors the ECG continuously and asks you to report chest pain, breathlessness, dizziness, or leg fatigue throughout. The target endpoint is 85% of your maximum predicted heart rate (calculated as 220 minus your age in beats per minute). The test is stopped immediately if you develop significant chest pain, severe breathlessness, dizziness or presyncope, dangerous arrhythmia, marked ST segment changes, a fall in systolic blood pressure of more than 10 mmHg, or if you request to stop. Recovery monitoring continues for 5–10 minutes while you sit or lie on the adjacent couch.

A cardiologist interprets the combined findings from ECG, heart rate, blood pressure, symptoms, and exercise duration. Key result parameters: Exercise capacity — measured in metabolic equivalents (METs); completing stage 3 of the Bruce protocol (achieving 10 METs) suggests a good functional capacity and prognosis; achieving fewer than 5 METs indicates poor functional capacity and higher cardiovascular risk. Chronotropic response — failure to achieve at least 85% of maximum predicted heart rate (chronotropic incompetence) without medication interference suggests sinus node dysfunction or significant CAD. ST segment response — horizontal or downsloping ST depression of 1 mm or more in two or more contiguous leads at peak exercise or in early recovery is the classic positive (ischaemic) result; the greater the depression, the larger the territory involved, and the earlier it appears during exercise, the more significant the underlying coronary disease. ST elevation during exercise (rare) indicates severe transmural ischaemia or vasospasm. Blood pressure response — systolic blood pressure normally rises to 160–200 mmHg at peak exercise; exercise-induced hypotension (a fall of 10 mmHg or more) indicates severe multi-vessel CAD or LV dysfunction and is an indication to stop immediately. Symptomatic response and rhythm disturbances are also documented. The result is reported as negative (normal), equivocal (borderline), or positive (ischaemic), with the Duke Treadmill Score used for risk stratification.

A medically supervised exercise stress test carries a very small risk of serious adverse cardiac events — estimated at approximately 1 serious complication (cardiac arrest, sustained ventricular arrhythmia, or acute myocardial infarction) per 10,000 tests performed. The test is conducted with full resuscitation equipment immediately available (defibrillator, emergency medications, oxygen) and medical staff trained in advanced cardiac life support. Absolute contraindications include acute myocardial infarction within 2 days, unstable angina, uncontrolled heart failure, severe symptomatic aortic stenosis, and acute myocarditis. The exercise ECG has moderate diagnostic accuracy for significant obstructive CAD — sensitivity approximately 68% and specificity approximately 77% — meaning it misses up to one-third of significant disease (false negatives) and produces false positive results in around one-quarter of tests. Accuracy is significantly lower in women (higher false positive rate due to repolarisation differences) and in patients with left bundle branch block, left ventricular hypertrophy with strain pattern, digoxin therapy, or Wolff-Parkinson-White syndrome (all of which cause baseline ST changes that confound interpretation). The exercise ECG does not directly visualise coronary anatomy — CT coronary angiography (CTCA) or invasive coronary angiography remains the definitive anatomical investigation for CAD.