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ACS rule-out — UKMLA MCQ

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ModerateCardiologyACS rule-outUKMLAMRCP Part 1MRCEM SBAMRCGP AKT

A 40-year-old man is assessed in the emergency department after 45 minutes of constricting central chest pain radiating to his left arm. The pain began 90 minutes before his first blood sample and has now resolved. He has type 2 diabetes, smokes, and his father had a myocardial infarction aged 48 years. His observations and examination are normal. His ECG shows no acute ischaemic changes. The first high-sensitivity cardiac troponin I concentration is below the 99th percentile but is not below the assay-specific single-sample rule-out threshold. A validated clinical risk tool classifies him as being at moderate risk of myocardial infarction. What is the most appropriate next step?

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Correct answer: B — Continue observation and repeat high-sensitivity troponin using the validated local pathway

The correct answer is B. His typical ischaemic symptoms, cardiovascular risk factors, moderate clinical risk and early presentation mean that a normal ECG and one troponin value below the 99th percentile do not safely exclude NSTEMI. Because the result does not satisfy the assay-specific single-sample rule-out threshold, he should remain under observation for repeat high-sensitivity troponin testing at the interval specified by the validated local pathway. Immediate discharge is unsafe. Fibrinolysis is not indicated without STEMI or another qualifying reperfusion indication. CT coronary angiography is not routinely used as the initial investigation to rule out acute ACS in this situation. Exercise ECG is also inappropriate for acute rule-out and is not recommended to diagnose or exclude stable angina in people without known coronary disease.

Reference: National Institute for Health and Care Excellence. HTG552, High-sensitivity troponin tests for the early rule out of NSTEMI, recommendations 1.1–1.3, 2020. https://www.nice.org.uk/guidance/HTG552/chapter/1-Recommendations