I’ve had a couple questions recently about accelerated rule-out strategies – considering they’re in the ACEP Guidelines, but the AHA seems to endorse a viewpoint that any suspicion for cardiac chest pain needs to be taken to its bitter end with a provocative test. Unfortunately, an all-in strategy doesn’t mesh quite as well with reality where the costs are astronomical, and the yield abysmal.
Conveniently, this is another recent study highlighting the use of two sets of biomarkers, two hours apart – using conventional troponin assays. This is an observational cohort study in Australia and New Zealand investigating the feasibility of their stratification instrument, with the endpoints of “Major Adverse Cardiac Events” within 30 days – an endpoint that, for once, excludes revascularizations. Specifically, the decision protocol being evaluated includes:
– Negative troponins at 0 and 2 hours from presentation.
– No new ischemic changes on ECG.
– TIMI Score of zero.
Of their 1,976 enrolled patients, 392 met these criteria and were followed for 30 days. Their single miss was reported as an nSTEMI with two initially negative troponins who subsequently had a positive 12-hour troponin. Therefore, their sensitivity for 30-day MACE is statistically 98.1% to 99.9%. This is one of the eight patients in the low-risk cohort who underwent a revascularization procedure in the course of their routine care.
Essentially, using a normal EKG, two negative sets of enzymes, and a risk-stratification instrument – TIMI, Geneva, etc. – the evidence out there lets you have a discussion with the patient regarding their overall risk for a poor outcome. If you’re stuck in a zero-miss environment, then any of these 2-hour protocols will be of no use – they all have a non-negligible miss rate. But, if you have a grey area to work with, and an otherwise relatively low-risk patient, a quick two-hour troponin helps you catch a few extra fish you otherwise would have missed.
“2-Hour Accelerated Diagnostic Protocol to Assess Patients With Chest Pain Symptoms Using Contemporary Troponins as the Only Biomarker The ADAPT Trial”
www.ncbi.nlm.nih.gov/pubmed/22578923