Two questions at booking prevent most aborted or uninterpretable stress studies. First: can this patient walk far enough and fast enough to reach an adequate workload? Orthopaedic limitation, peripheral arterial disease, frailty and deconditioning are all obvious at the booking call and all invisible on the request form. A patient who will not achieve target heart rate should be booked for pharmacological stress from the start, not converted halfway through a treadmill protocol.
Second, for anyone going to a vasodilator study: what have they taken? Caffeine in any form, and methylxanthines such as theophylline and aminophylline, blunt the vasodilator response and can turn a positive study into a normal-looking one. So can dipyridamole taken as regular medication. The abstinence instruction has to reach the patient in a language they read, and it has to be asked again on arrival rather than assumed.
Both failures produce the same result — a test that is reported, filed and believed, but which never had the physiology behind it to exclude anything.
- Ask about exercise capacity at booking, not on the day
- Book pharmacological stress up front where target workload is unlikely
- Ask specifically about coffee, tea, cola, chocolate and energy drinks — patients do not think of tea as caffeine
- Check for theophylline, aminophylline and regular dipyridamole in the drug list
- Re-ask on arrival; the instruction sheet is not evidence that it was followed
Why it matters
A falsely reassuring perfusion study is worse than no study, because it closes the question.
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