Four in ten paramedic STEMI activations end with a different diagnosis

Design

Retrospective statewide ambulance registry cohort

Population

7,205 patients with paramedic-suspected STEMI and a recorded discharge diagnosis, Victoria, Australia

Primary outcome

Final diagnosis and mortality

Effect

STEMI confirmed in 60.1%; non-cardiac diagnosis HR 1.75 (1.47–2.09) for long-term death vs STEMI

A statewide registry from Victoria, Australia, followed 8,077 patients for whom paramedics activated a STEMI pathway between 2020 and 2025. Of the 7,205 with a recorded discharge diagnosis, 60.1% had confirmed STEMI. The rest had other acute coronary syndromes (11.4%), other cardiac diagnoses (10.5%), non-cardiac diagnoses (8.5%) or symptom-based codes (9.4%).

This was a sick group regardless of label: in-hospital mortality was 8.6%, and 17.5% died over a median 2.8 years. After adjustment, patients whose final diagnosis was non-cardiac had higher long-term mortality than those with confirmed STEMI (HR 1.75, 95% CI 1.47–2.09).

The authors caution against reading this as over-activation. Prehospital activation is made without troponin, imaging or angiography, and a pathway that never triggers falsely will miss true STEMI. The message for the emergency department is that a STEMI alert is a starting hypothesis: the patient who turns out not to have one may have aortic dissection, sepsis, pulmonary embolism or another condition that is at least as dangerous.

• Keep rapid reperfusion access for paramedic STEMI activations; most were confirmed.
• Re-examine the ECG and the patient on arrival, looking for STEMI mimics.
• Consider aortic dissection, pulmonary embolism and sepsis when the picture does not fit.
• Patients cancelled from the STEMI pathway still carried high mortality; do not de-prioritise them.

Why it matters

The patient stood down from the catheter laboratory can be the sickest one in the department.

Don't overread it

This describes the pathway population; it does not show that prehospital activation is too liberal.

The statistics, in plain English

A hazard ratio of 1.75 means death during follow-up was about 75% more frequent in the non-cardiac group than in confirmed STEMI, after adjustment. Registry data show association, and 11% of patients had no recorded diagnosis.

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