Initial assessment
In 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 withheld. In these cases, consider alternative studies such as perfusion scintigraphy, stress echocardiography, or coronary CT angiography.
With relative contraindications (moderate aortic stenosis, electrolyte disturbances, BP ≥200/110 mmHg, significant tachy-/bradyarrhythmias, obstructive HCM, high-grade AV block, physical/mental limitations), postponing or substituting the test should be considered until clinical stabilisation.
Limitations to diagnostic accuracy
The exercise test is less reliable in women (more false positives), older adults, patients with a non-interpretable resting ECG (LBBB, paced rhythm), those taking beta-blockers or other negative chronotropes, in multivessel coronary disease, and in individuals with physical limitations (obesity, musculoskeletal disease). In these scenarios, consider imaging-based tests.
Medication influence
Beta-blockers
Lower heart rate and ischaemic burden, leading to false negatives and submaximal tests.
Calcium channel blockers (e.g., verapamil)
Reduce heart rate and cause vasodilation, potentially masking symptoms.
Nitrates
May attenuate signs and symptoms of ischaemia.
Antiarrhythmics
Alter the ECG tracing and hinder interpretation.
Digoxin
Produces “scooped” ST-segment depression, associated with false positives.
Diuretics and insulin
Diuretics may induce electrolyte changes; insulin may cause hypoglycaemia, confounding symptoms with ischaemia.
Baseline ECG abnormalities
Certain patterns preclude or limit interpretation: complete left bundle branch block, paced rhythm, pre-excitation, left ventricular hypertrophy with secondary repolarisation, digoxin effect, and marked nonspecific repolarisation changes. In these cases, prefer imaging-based stress testing.
Functional capacity assessment
Estimated in METs using predictive formulae: 14.7 − 0.11 × age (men); 14.7 − 0.13 × age (women). Capacity is considered preserved when the achieved value is at least the predicted value. Capacity <7 METs in men or <5 METs in women is associated with poorer prognosis.
Hemodynamic response
Heart rate: target ≥85% of age-predicted maximum (220 − age). Failure to reach this defines chronotropic incompetence, which may reflect autonomic dysfunction, nodal conduction disease, or drug effect.
Blood pressure: a fall in systolic BP ≥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
Ischaemia criteria: horizontal or downsloping ST-segment depression ≥1 mm, measured 80 ms after the J point in ≥2 contiguous leads; ST elevation ≥1 mm in leads without Q waves suggests transmural ischaemia or coronary spasm.
Poor prognosis: ST depression >2 mm, involvement of ≥5 leads, early onset (<6 min), or persistence >6 min into recovery. Exercise-induced arrhythmias such as non-sustained ventricular tachycardia or rapid atrial fibrillation also indicate higher risk.
Clinical symptoms
Value symptoms such as typical angina, limiting dyspnoea, dizziness, presyncope or syncope, which may indicate ischaemia, ventricular dysfunction, or significant arrhythmias. Absence of symptoms does not exclude coronary disease and should be integrated with other findings.
Recovery phase
A heart-rate drop ≥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. Also assess haemodynamic stability, ongoing symptoms, and any arrhythmias.
Final classification
Negative test: good functional capacity, no symptoms, and normal ECG — low risk, no further testing needed.
Positive test: ST changes, typical symptoms with ECG abnormalities, low functional capacity, or high-risk criteria. The Duke treadmill score (exercise time − [5 × angina index] − [4 × ST depression in mm]) should be calculated for risk stratification.
Inconclusive test: non-interpretable baseline ECG, submaximal workload, vague symptoms, or drug interference. Repeat or switch to an imaging stress test.
High-risk non-ischaemic findings: ventricular arrhythmias, advanced blocks, hypotension, poor heart-rate recovery, or syncope — require urgent referral.
Early termination: due to limiting symptoms, haemodynamic instability, severe arrhythmias, claudication, or technical issues — consider additional investigations, including imaging or coronary angiography, according to overall risk.
