A faster heart-attack blood test was safe, and saved emergency departments no time at all
PRESC1SE-MI covered 67,624 chest-pain presentations at 19 hospitals. The one-hour troponin pathway matched the three-hour one on safety, and median length of stay was identical: 309 minutes.
| Group | Value (minutes) |
|---|---|
| 0/1 h pathway | 309 |
| 0/3 h pathway | 309 |
Someone arrives at an emergency department with chest pain. The question of whether they are having a heart attack is settled largely by measuring cardiac troponin twice, and the interval between those two blood draws determines how long they occupy a bed.
Guidelines recommend a one-hour interval. Many hospitals still use three. PRESC1SE-MI, published in The Lancet on 29 August and presented at ESC Congress 2026, is the largest test of what actually happens when a hospital switches — and it found the faster pathway was safe, and saved no time [s1].
What the trial did
PRESC1SE-MI was an international, pragmatic, stepped-wedge, cluster-randomised, masked-endpoint trial at 19 hospitals in ten countries [s1]. It included consecutive adults presenting to the emergency department with acute non-traumatic chest discomfort and suspected myocardial infarction [s1].
Hospitals already using a 0/3 h pathway — blood draws at 0 and 3 hours — were randomly allocated to implement the 0/1 h pathway after either 6 months or 12 months [s1]. The randomised unit was the hospital, not the patient, which is what makes this an implementation trial rather than a diagnostic accuracy study.
There were two coprimary outcomes tested against different standards. Safety was a composite of death from any cause or new type 1 myocardial infarction within 30 days, tested for non-inferiority with a margin of 1.3 on the odds ratio [s1]. Efficacy was emergency department length of stay, tested for superiority [s1].
Between 1 December 2020 and 31 December 2024, 71,983 consecutive patient presentations were screened, of which 67,624 (93.9%) met the eligibility criteria [s1]. Median age was 59 years (IQR 46 to 73); 29,954 presentations (44.3%) were in female patients and 37,670 (55.7%) in male patients [s1]. Among presentations with available data, 13,753 of 62,060 (22.2%) were in patients with known coronary artery disease, and 5,855 presentations (8.7%) had an adjudicated index diagnosis of myocardial infarction [s1].
In total, 36,464 presentations were managed with the 0/3 h pathway and 31,160 with the 0/1 h pathway [s1].
What happened
On safety, death from any cause or new type 1 myocardial infarction occurred in 454 presentations (1.2%) in the 0/3 h group and 341 (1.1%) in the 0/1 h group, an adjusted odds ratio of 0.93 (95% CI 0.77 to 1.13) with a non-inferiority p value of 0.0004 [s1]. Non-inferiority was met.
On efficacy, the median emergency department length of stay was 309 minutes (IQR 203 to 470) under the 0/3 h pathway and 309 minutes (IQR 207 to 474) under the 0/1 h pathway — a ratio of adjusted median times of 1.00 (95% CI 0.97 to 1.02, two-sided p=0.65) [s1].
Identical to the minute.
Why the null is the finding
Cutting two hours out of a diagnostic protocol should shorten a stay. That it did not is the trial's substantive result, and the investigators state the implication directly: implementation of the 0/1 h pathway alone should not be expected to improve emergency department throughput [s1].
The word carrying the weight is "alone". A troponin interval is one step inside a process that also includes triage, clinical assessment, imaging, specialist review, bed availability and discharge paperwork. If the binding constraint on how long a patient stays sits somewhere other than the blood test, removing two hours from the blood test does not move the total — the slack simply relocates.
This is a familiar pattern in operations, and an unfamiliar one in clinical trials, because clinical trials rarely randomise a process rather than a treatment. A conventional diagnostic study would have measured time to rule-out decision and reported a large improvement. PRESC1SE-MI measured time in the department and reported none.
What it does and does not establish
It establishes that switching to the 0/1 h pathway, in hospitals that had not previously used it, did not increase 30-day death or new type 1 myocardial infarction within the prespecified margin [s1]. That is a reassurance about safety at scale — 67,624 presentations is a substantial denominator [s1].
It does not establish that the 0/1 h pathway is useless. Shorter time to a decision has value to patients and clinicians even when it does not free a bed, and the trial did not measure patient experience.
It also does not describe hospitals that had already adopted the faster pathway; the trial deliberately recruited sites that had not [s1]. And length of stay was measured under whatever local conditions each of the 19 hospitals had, across ten countries, between 2020 and 2024 [s1] — a period that includes substantial disruption to emergency care.
The trial was funded by the Swiss National Science Foundation, the Swiss Heart Foundation, University Hospital Basel, the University of Basel, the Foundation for Cardiovascular Research Basel, Fondazione Ricerca Molinette, Idorsia and Roche, and registered as NCT05649384 [s1].
Where it lands in the same week's definitional change
The result arrived days after the Fifth Universal Definition of Myocardial Infarction, which introduces accelerated diagnostic pathways using high-sensitivity troponin assays and provides guidance for the settings where troponin interpretation is difficult [s2]. The definition also retains sex-specific 99th percentile upper reference limits as the basis for identifying myocardial injury [s2].
The two documents fit together awkwardly in a useful way. One recommends the faster pathway; the other shows that adopting it does not, by itself, do the thing hospitals usually adopt it for.
What to watch
Whether hospitals that have already switched report the same absence of throughput benefit, and whether implementation research starts to accompany diagnostic guideline changes as a matter of course. The gap between what a pathway can do and what a department gets from it is exactly the gap this trial was built to measure.
This article describes trial results. It is not medical advice, and nothing here should be used to make decisions about care.
Sources
- Safety and efficacy of the 0/1 h pathway for myocardial infarction in the emergency department: an international, pragmatic, stepped-wedge, cluster-randomised, controlled trial, The Lancet, 29 August 2026
- Fifth Universal Definition of Myocardial Infarction (2026), Global Heart, 28 August 2026
Sources
- Safety and efficacy of the 0/1 h pathway for myocardial infarction in the emergency department: an international, pragmatic, stepped-wedge, cluster-randomised, controlled trial — The Lancet , August 29, 2026
- Fifth Universal Definition of Myocardial Infarction (2026) — Global Heart , August 28, 2026
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