Suspected Heart Attack May Have Another Diagnosis

A concerning ECG, a patient with chest pain and a decision that cannot wait. Prehospital STEMI assessment often means acting before the complete diagnostic picture is available.

Sometimes, hospital investigations establish a different diagnosis. That does not automatically mean the ambulance crew made the wrong decision. Equally, it does not mean every activation was justified.

The important question is whether the decision was reasonable given the information available at the time.

What did the study find?

Lankaputhra and colleagues examined suspected STEMI attendances in an Australian statewide ambulance registry, using hospital follow-up data from January 2020 to June 2025.

Of 8,077 attendances, 7,205 had a recorded discharge diagnosis. The findings were:

Final diagnosis group

Percentage
Confirmed STEMI 60.1%
Non-ST-elevation acute coronary syndrome or other coronary syndromes 11.4%
Other cardiac diagnoses 10.5%
Non-cardiac diagnoses 8.5%
Symptom-based diagnoses 9.4%

Patients with non-cardiac diagnoses had higher adjusted longer-term mortality than those with confirmed STEMI. A different diagnosis therefore did not necessarily mean a low-risk patient (Lankaputhra et al., 2026). (pubmed.ncbi.nlm.nih.gov)

Why 60% is not a paramedic accuracy score

It would be tempting to turn this into a headline saying that paramedics got four out of ten STEMIs wrong. That would misrepresent the research.

The study started with patients already selected for a suspected-STEMI pathway. It did not assess every patient with chest pain or identify all missed STEMIs outside that pathway.

There are also limitations: this was retrospective Australian research using discharge diagnoses, and 10.8% of attendances lacked a recorded diagnosis. Only the abstract was accessible for this article, so a full-text critical appraisal was not possible. (pubmed.ncbi.nlm.nih.gov)

Our interpretation is that these findings should prompt thoughtful review of decisions, not an automatic verdict on the clinician who made them.

ST elevation is a finding, not the whole diagnosis

The ECG needs to be interpreted alongside the patient’s symptoms, history, observations and examination.

Conditions associated with ST elevation include pericarditis, early repolarisation, left ventricular hypertrophy, left bundle branch block, ventricular pacing, ventricular aneurysm and Takotsubo cardiomyopathy. Some are relatively familiar patterns. Others represent serious illness requiring urgent assessment.

A curved or concave ST segment is not a reliable shortcut to reassurance. Acute STEMI can also produce concave ST elevation. Nor does recognising a possible mimic exclude simultaneous acute coronary disease (Burns and Buttner, 2026). (litfl.com)

The practical lesson is not to memorise a list and then dismiss an ECG because it resembles one example. It is to recognise uncertainty and use the appropriate clinical support.

What does this mean for UK ambulance practice?

The study does not justify changing UK STEMI activation thresholds or delaying an established pathway.

NICE recommends immediate assessment for reperfusion in acute STEMI. Its chest-pain guidance also emphasises that a normal resting ECG does not exclude acute coronary syndrome. Where uncertainty remains, serial ECGs and comparison with previous recordings can help, but obtaining an ECG must not delay transfer to hospital (NICE, 2010; NICE, 2020). (nice.org.uk, nice.org.uk, dejavu.org)

For ambulance clinicians, the useful balance is between urgency and an open mind.

Follow current JRCALC guidance and your service’s cardiac pathway. Seek clinical advice or transmit the ECG where this is available and indicated. Communicate what concerns you, what remains uncertain and how the patient is changing.

This article is an evidence discussion, not a replacement for those operational instructions.

Avoiding the two traps

There are two easy mistakes in a difficult assessment.

The first is anchoring: deciding early that the patient has a STEMI and then interpreting everything else through that diagnosis.

The second is premature reassurance: deciding that the tracing is probably a mimic and allowing that explanation to override concerning symptoms or deterioration.

A useful pause is to ask:

* What supports my working diagnosis?
* What does not fit?
* What other serious explanation am I considering?
* What information would change my decision?
* Have I clearly communicated the uncertainty?

These are reflective prompts, not additional hurdles that must be completed before an urgent pre-alert.

Learning from the final diagnosis

Hospital feedback can be valuable, but the final diagnosis should start a discussion rather than end it.

A case review should consider the symptoms, ECG, observations, available advice and pathway criteria at the time. It should also ask whether there was anything the crew could reasonably have recognised or done differently.

A changed diagnosis alone cannot answer those questions.

Useful feedback explains the reasoning: which ECG features mattered, what later investigations clarified and what can be learnt for the next patient. Simply telling a crew that “it was not a STEMI” offers very little educational value.

References

• Burns, E. and Buttner, R. (2026) ‘The ST segment’, Life in the Fast Lane, 24 September. Available at: https://litfl.com/st-segment-ecg-library/ (Accessed: 14 October 2026).
• Lankaputhra, M. et al. (2026) ‘Final diagnoses and outcomes after paramedic-suspected ST-segment elevation myocardial infarction’, Annals of Emergency Medicine. Published online 6 October. doi: 10.1016/j.annemergmed.2026.07.027. Abstract accessed via PubMed (Accessed: 14 October 2026).
• National Institute for Health and Care Excellence (2010, updated 2016) Recent-onset chest pain of suspected cardiac origin: assessment and diagnosis. CG95. Available at: https://www.nice.org.uk/guidance/cg95 (Accessed: 14 October 2026).
• National Institute for Health and Care Excellence (2020) Acute coronary syndromes. NG185. Available at: https://www.nice.org.uk/guidance/ng185 (Accessed: 14 October 2026).