Which of the following is a relative indication to stop an exercise test?

• A. Systolic blood pressure exceeding 180.
• B. SpO2 ≤88%.
• C. Bundle-branch block indistinguishable from ventricular tachycardia.
• D. Mild fatigue.

Answer: (C)

During an exercise test, safety decisions hinge on signals that tell us whether it’s still wise to continue. If a bundle-branch block appears and that block cannot be distinguished on the ECG from ventricular tachycardia, there’s real danger because VT is a potentially life-threatening rhythm and you can’t reliably interpret whether ischemia or dangerous pacing is occurring. That diagnostic ambiguity makes continuing the test risky, so stopping the test is a cautious, relative indication. The other options don’t carry the same level of safety concern in this exact context: fatigue can be a normal response to exercise, while desaturation or blood‑pressure thresholds tend to prompt stopping for more immediate clinical reasons, not the specific uncertainty about an arrhythmia.