Initial assessment
In the clinical interpretation of the exercise stress test, the first step is to check for absolute contraindications. If present — acute myocardial infarction <48 h, high-risk unstable angina, uncontrolled symptomatic arrhythmias, symptomatic severe aortic stenosis, decompensated heart failure, pulmonary embolism, acute aortic dissection, acute myocarditis or pericarditis — the test should be suspended. In these cases, consider alternative investigations such as perfusion scintigraphy, stress echocardiography or coronary CT angiography.
In relative contraindications, moderate aortic stenosis, electrolyte disturbances, hypertension ≥200/110 mmHg, significant tachy/bradyarrhythmias, obstructive hypertrophic cardiomyopathy, high-grade AV block, physical or mental limitations, postponement or replacement of the test should be considered until clinical stabilisation.
Limitations to diagnostic accuracy
The exercise stress test has lower reliability in women, with more false positives, older patients, patients with a non-interpretable baseline ECG, LBBB or pacemaker, those receiving beta-blockers or other negative chronotropic drugs, in multivessel coronary artery disease and in patients with physical limitations, obesity or osteoarticular disease. In these situations, imaging-based tests should be considered.
Influence of drugs
Beta-blockers
They reduce heart rate and ischaemic burden, leading to false negatives and submaximal tests.
Calcium-channel blockers, for example verapamil
They reduce heart rate and promote vasodilation, masking symptoms.
Nitrates
They may attenuate signs and symptoms of ischaemia.
Antiarrhythmics
They alter the ECG tracing and make interpretation more difficult.
Digoxin
It causes “scooped” ST-segment depression, associated with false positives.
Diuretics and insulin
Diuretics may induce electrolyte abnormalities; insulin may cause hypoglycaemia, confusing symptoms with ischaemia.
Baseline ECG abnormalities
Certain patterns make interpretation impossible or limited: complete left bundle branch block, pacemaker rhythm, pre-excitation syndrome, left ventricular hypertrophy with secondary repolarisation changes, digoxin use and marked non-specific repolarisation abnormalities. In these cases, complementary imaging-based tests should be preferred.
Assessment of functional capacity
Functional capacity is estimated in METs using predictive formulas: 14.7 − 0.11 × age for men; 14.7 − 0.13 × age for women. Capacity is considered preserved when the achieved value is equal to or greater than predicted. Capacity below 7 METs in men or 5 METs in women is associated with an unfavourable prognosis.
Haemodynamic response
Heart rate: target ≥85% of the predicted maximum, 220 − age. Failure to reach this value defines chronotropic incompetence, which may reflect autonomic dysfunction, nodal block or drug effect.
Blood pressure: a fall in systolic pressure ≥10 mmHg during exercise suggests ventricular dysfunction or haemodynamic obstruction. A hypertensive response ≥210 mmHg in men or ≥190 mmHg in women is associated with higher future cardiovascular risk.
Electrocardiographic response
Criteria for ischaemia: ST-segment depression ≥1 mm, horizontal or downsloping, measured 80 ms after the J point in ≥2 contiguous leads; ST elevation ≥1 mm in leads without Q wave suggests transmural ischaemia or coronary spasm.
Poor prognosis: ST depression >2 mm, involvement of ≥5 leads, early onset, <6 min, or persistence >6 min in recovery. Exercise-induced arrhythmias, such as non-sustained ventricular tachycardia or rapid atrial fibrillation, also indicate increased risk.
Clinical symptoms
Symptoms such as typical angina, limiting dyspnoea, dizziness, presyncope or syncope should be valued, as they may indicate ischaemia, ventricular dysfunction or serious arrhythmias. Absence of symptoms does not exclude coronary artery disease and should be integrated with the remaining data.
Recovery phase
A fall in heart rate ≥12 bpm in the first minute is considered normal; lower values suggest autonomic dysfunction and worse prognosis. Persistence of ST-segment depression >6 min indicates extensive or diffuse ischaemia. Haemodynamic stability, persistent symptoms and possible arrhythmias should also be assessed.
Final classification
Negative test: good functional capacity, absence of symptoms and normal ECG — low risk, with no need for additional investigation.
Positive test: ST changes, typical symptoms with ECG changes, low functional capacity or poor-prognosis criteria. The Duke score should be calculated, exercise time − [5 × angina grade] − [4 × ST depression, mm], for risk stratification.
Inconclusive test: non-interpretable baseline ECG, submaximal workload, vague symptoms or drug interference. It should be repeated or replaced by an imaging-based test.
High-risk non-ischaemic findings: ventricular arrhythmias, advanced blocks, hypotension, poor heart-rate recovery or syncope — these require urgent referral.
Prematurely interrupted test: due to limiting symptoms, haemodynamic instability, severe arrhythmias, claudication or technical problems — further investigation should be considered, including imaging tests or coronary angiography, depending on global risk.
