Graded exercise with continuous ECG, looking for ischaemic change
Expansion
The test: graded exercise, usually on a treadmill by the Bruce protocol, with continuous ECG, blood pressure and symptoms, to a target heart rate or symptom limitation.
Positive features
- Horizontal or downsloping ST depression of 1 mm or more, 80 ms after the J point. Upsloping depression is much less specific
- ST elevation in leads without Q waves, which suggests transmural ischaemia
- Fall in systolic blood pressure, a marker of severe disease
- Typical angina reproduced at low workload
- Poor functional capacity, or a slow heart rate recovery
Reasons to stop: chest pain, fall in systolic blood pressure of 10 mmHg or more, significant arrhythmia, ST elevation, 3 mm or more of depression, dizziness, ataxia, pallor, or the patient’s request.
Why it has fallen out of diagnostic use: sensitivity is only around 68 per cent and specificity 77 per cent, so in a population with intermediate probability it generates a substantial number of false positives and negatives. UK guidance now recommends CT coronary angiography as the first line test for stable chest pain.
When the ECG is uninterpretable for ischaemia, and functional imaging is needed instead: left bundle branch block, paced rhythm, pre-excitation, digoxin, left ventricular hypertrophy with strain, and resting ST abnormality.
Where it still has value: assessing functional capacity in METs, exercise induced arrhythmia, chronotropic incompetence, blood pressure response, risk stratification in known disease, and assessing symptoms in valve disease such as asymptomatic severe aortic stenosis.
Alternatives: stress echocardiography, myocardial perfusion imaging and stress cardiac MRI, all of which use pharmacological stress where the patient cannot exercise.