ECG Criteria and Diagnostic Performance for Myocardial Ischemia During Exercise Stress Testing

Diagnostic ECG Criteria

• Horizontal or downsloping ST‑segment depression ≥ 1 mm measured 80 ms after the J‑point, with assessment at 2 minutes into recovery, is the primary criterion for detecting myocardial ischemia (American Heart Association) 1
• The number of leads showing ST‑segment depression and the depth of the depression correlate with the extent of ischemia – more involved leads and deeper depressions indicate more extensive coronary disease (American College of Cardiology) 2

Overall Diagnostic Performance

• Exercise ECG has a pooled sensitivity of ~61 % and specificity of 70–77 % for identifying obstructive coronary artery disease (American Heart Association) 1

Patient Preparation and Prerequisites

• Patients must be able to achieve maximal exercise capacity and must withhold β‑blockers for 24–48 h before testing (American Heart Association) 1, 3
• A baseline ECG that is normal or shows only minimal ST‑T abnormalities (< 0.5 mm) is required (American Heart Association) 1, 3
• An intermediate pre‑test probability of CAD (15–85 %) yields the optimal diagnostic yield (European Society of Cardiology) 4

Conditions That Preclude Accurate ECG Interpretation

• Ventricular paced rhythm makes ECG interpretation unreliable (American Heart Association; European Society of Cardiology) 1, 4
• Wolff‑Parkinson‑White syndrome precludes reliable interpretation (European Society of Cardiology) 4
• Resting ST‑segment depression ≥ 0.5 mm invalidates the test (American Heart Association; American Heart Association) 1, 3
• Digitalis therapy can produce false‑positive ST changes, limiting interpretability (American Heart Association; American Heart Association) 1, 3
• Complete right bundle‑branch block reduces diagnostic accuracy to ~75 % (American Heart Association) 1

Factors That Improve Diagnostic Accuracy

When to Bypass Exercise ECG and Proceed Directly to Stress Imaging

• Baseline ST‑segment depression ≥ 0.1 mV (European Society of Cardiology) 4
• Pre‑test probability > 85 % (European Society of Cardiology) 4
• Left ventricular ejection fraction < 50 % (European Society of Cardiology) 4
• Prior coronary revascularization (PCI or CABG) (European Society of Cardiology) 4
• Women with suspected CAD – imaging modalities demonstrate superior accuracy (American College of Cardiology) 5, 2
• Inability to achieve adequate exercise – pharmacologic stress with imaging is recommended (European Society of Cardiology; American College of Cardiology) 4, 2

Medication Effects on Test Sensitivity

• Anti‑ischemic drugs (e.g., nitrates, calcium‑channel blockers) lower the sensitivity of exercise ECG by reducing myocardial workload, increasing the risk of false‑negative results (American Heart Association; American Heart Association) 1, 3
• β‑blockers must be withheld 24–48 h before testing to allow an appropriate heart‑rate response (American Heart Association; American Heart Association) 1, 3
• Performing the test while patients remain on anti‑ischemic therapy is appropriate only for evaluating symptom control, not for diagnostic purposes (European Society of Cardiology) 4

Diagnostic Approach to Suspected Coronary Artery Disease

Pre-Test Probability Assessment

• The European Society of Cardiology recommends calculating pre-test probability using the Risk Factor-weighted Clinical Likelihood model incorporating age, sex, symptom type, and cardiovascular risk factors to determine whether testing is appropriate 6, 7
• For patients with very low probability (≤5%) of coronary artery disease, the European Heart Journal suggests deferring further testing due to more harm than benefit from false positives 6, 7
• The American College of Cardiology recommends coronary artery calcium scoring for patients with low probability (>5-15%) to reclassify patients 6

Stress Testing Modalities

• The European Heart Journal recommends exercise stress imaging (echo or SPECT/PET) for patients with intermediate-to-high pre-test probability (>15-85%) who can exercise with a normal ECG, due to superior sensitivity 8, 6, 7, 9
• For patients who cannot exercise, the European Society of Cardiology suggests dobutamine stress echo (if no LBBB/pacing) or vasodilator stress perfusion imaging 9, 10
• The American Heart Association recommends vasodilator stress perfusion imaging (adenosine/dipyridamole) for patients with LBBB or paced rhythm, regardless of exercise capacity 9, 10

Diagnostic Performance of Stress Testing Modalities

• Exercise ECG has a sensitivity of 45-50% and specificity of 90% 8, 11
• Exercise stress echocardiography has a sensitivity of 80-85% 8, 11
• Vasodilator stress SPECT has a sensitivity of 90-91% 8, 11
• Vasodilator stress PET has a sensitivity of 81-97% 8, 11, 6, 7

Contraindications and Pitfalls

• The European Heart Journal advises against performing exercise ECG in patients with baseline ST depression >0.1 mV or on digitalis 12
• The American College of Cardiology recommends avoiding dobutamine or exercise stress in LBBB/paced rhythm due to false-positive septal wall motion abnormalities 9, 10
• The European Society of Cardiology suggests not defaulting to pharmacologic stress in elderly patients based on age alone, if they can exercise ≥5 METs 9