Exercise Testing
Choosing the test
A maximal GXT with 12-lead ECG, blood pressure, heart rate, RPE, and symptom monitoring is standard for diagnosis and prognosis. Ramp protocols produce smoother data; Bruce is the reference standard; modified Bruce or Naughton suits low-capacity patients; cycle ergometry helps with orthopedic, balance, or artifact problems; arm ergometry serves lower-limb impairment. Cardiopulmonary exercise testing is indicated when you need peak VO2, ventilatory threshold, or an RER ≥1.10 to confirm maximal effort.
Interpreting the trace
ST depression of ≥1 mm, horizontal or downsloping, measured 80 ms after the J point is the classic ischemic threshold; upsloping depression is less specific. Also note chronotropic incompetence, a blunted or falling systolic pressure, ventricular arrhythmias, and peak functional capacity in METs (under 5 METs is a poor prognostic sign).
Termination
Absolute indications include ST elevation, a drop in systolic pressure >10 mmHg with signs of ischemia, moderate-severe angina, central nervous system symptoms, sustained ventricular tachycardia, and the patient's request to stop. Relative indications include >2 mm ST depression, significant arrhythmias, and marked hypertension.
Traps
The 6-minute walk test is submaximal; do not label it a maximal GXT. Age-predicted heart rate has a standard deviation of about 10-12 bpm, so a lower-than-predicted peak may be normal, and reaching 85% of predicted is not by itself a reason to stop.
Worked example
A 60-year-old peaks at 140 bpm. Predicted maximum is 220 - 60 = 160, so the patient achieved 87.5%, an acceptable effort level. Then ask what limited the test: symptoms, blood pressure, ECG, or leg fatigue.