Suspected STEMI in the field: how often are we right, and what lies behind the other 40 %

A large Australian registry linked paramedic-suspected STEMI to the hospital discharge diagnosis. Three in five suspicions were confirmed — and the worst prognosis was not in the patients where we were “wrong” towards a coronary cause.

When a 12-lead ECG shows ST elevation and the patient has chest pain, we decide within minutes: pre-alert, destination PCI centre, lights and sirens. How often is that judgement correct, and what happens to patients in whom STEMI is ultimately not confirmed? Part five of our Journal Club reviews a registry study from Annals of Emergency Medicine (October 2026) which shows, across more than 8,000 attendances, that “false-positive STEMI” is not a group we can stop thinking about.

Clinical question (PICO)

The study is not interventional but diagnostic and prognostic. We therefore framed the clinical question around what we actually do in the field — establish a working diagnosis from the ECG and the clinical picture.

Methods

The authors (Lankaputhra et al., Monash University and Ambulance Victoria) used the statewide VASQI registry (Victorian Ambulance STEMI Quality Initiative), which captures every case in which paramedics suspected STEMI. The registry was linked to hospital data for January 2020 — June 2025. Principal discharge diagnoses were grouped into five categories, and associations between diagnostic group and outcomes were estimated with multivariable logistic and Cox regression (odds ratios and hazard ratios with 95 % confidence intervals).

Results

Of 8,077 suspected-STEMI attendances with hospital follow-up, 7,205 (89.2 %) had a recorded discharge diagnosis and formed the main analytic cohort. In 872 attendances (10.8 %) the diagnosis was missing.

Treatment and mortality in the whole cohort

Long-term mortality by final diagnosis (adjusted, vs. confirmed STEMI)

In other words: patients in whom STEMI was not confirmed were not “healthier”. After adjustment, their long-term prognosis was comparable to true STEMI — and those with a noncardiac cause did markedly worse.

Critical appraisal

How it fits with existing data

False-positive activations are not new. In a Minnesota registry (Larson et al., JAMA 2007), 14 % of patients with suspected STEMI had no culprit artery at angiography and 9.5 % had no significant coronary disease. An Australian study using ECG transmission and interventional cardiologist consultation (Faour et al., 2022) reported only 4.9 % false-positive activations — at the cost of a second review of every ECG.

The other side of the coin — STEMI we do not see. A New Zealand study (Liao et al., Open Heart 2022) found that paramedics’ initial impression was STEMI in only 50.7 % of patients who ultimately had one. STEMI patients whom the crew thought had a non-coronary problem had much higher 30-day mortality; after adjustment the difference shrank but did not disappear (HR 1.48).

ECG mimics. A survey of paramedics in Saudi Arabia (Alrumayh et al., 2022) found that most respondents misread ECGs that mimic STEMI — left bundle branch block was correctly identified by 14.8 %, pericarditis by 10.9 %. The sample was small, but the direction is clear: mimics are the weakest point of interpretation.

Beyond STEMI criteria. Some acute coronary occlusions do not meet classic ST-elevation criteria (the “occlusion MI” concept). A recent scoping review (Grimes and Maria, Acad Emerg Med 2026), however, notes that the evidence for individual non-ST-elevation patterns is still heterogeneous. For paramedics, the lesson is humility with a negative ECG rather than new activation criteria.

Comparison with Slovak practice and legislation

In Slovakia, a paramedic-only RZP crew also records the 12-lead ECG and establishes a working diagnosis. Routing of STEMI patients follows the recommendation of the Slovak Society of Cardiology and the Slovak Society of Emergency and Disaster Medicine (Studenčan et al., 2013): ECG within 10 minutes of first contact, estimation of the “ECG-to-PCI” interval (travel time to the PCI centre + 30 minutes), direct transport to the PCI centre without intermediate stops when the estimate is 120 minutes or less, and early pre-alert of the cath lab team. In practice, the crew activates the PCI centre directly through the CDS App mobile application, not via the dispatch centre. The app is also used to send the 12-lead ECG to the cardiac centre. The 2023 ESC Guidelines for acute coronary syndromes share the same principles — ECG within 10 minutes and, after a prehospital working diagnosis of STEMI, direct transfer to a PCI centre bypassing the emergency department.

The Australian data transfer to Slovak conditions with two caveats. First, we have no national registry linking paramedic-suspected STEMI to the discharge diagnosis — so we do not know how many of our suspicions are confirmed. Second, some suspected-STEMI patients in Slovakia are managed by a physician-led RLP crew; thrombolysis and pharmacotherapy beyond Section 3(1) are within the physician’s scope, so for RZP crews the task is recognition, timely request for an RLP crew or HEMS depending on local conditions, preparation and a high-quality handover.

Take-home points for the field

Practical implications for paramedics