Missed myocardial infarction highlights challenges of diagnosing atypical presentations

Atypical presentations will inevitably present diagnostic challenges. However it is important to be aware of atypical presentations that commonly give rise to missed diagnoses, such as acute coronary syndrome in female patients.

Ms Q was 68, with a medical history that included osteopaenia and an adverse reaction to morphine.

She attended a hospital emergency department (ED) after an accident while exercising on a stationary cycle. She explained that she had slipped and struck her ribcage on the handlebars. She described the event as “mechanical” rather than in terms suggesting a medical episode.

At the time of the event she experienced a sharp pain. This was not debilitating but persisted and the next day, caused her to take paracetamol, ibuprofen and codeine. She began to experience nausea and pain in her upper abdomen and left lower ribs, which continued to intensify. When she arrived at the ED that evening her vital signs were stable and she rated the pain at 5 out 10.

A clinician from the rapid assessment team (RAT) examined her 2 hours after her arrival. They noted Ms Q was dry retching, pale and appeared uncomfortable, but had normal vital signs, a clear chest and no difficulty breathing. She had no abdominal tenderness and the results of an abdominal ultrasound were normal. They formed a preliminary diagnosis of adverse reaction to the codeine rather than a delayed presentation of trauma.

Two hours later a second clinician examined Ms Q and came to the same diagnosis.

Ms Q was admitted to the short stay unit for a chest x-ray, blood tests and medication for pain and nausea. However, while this treatment plan was being implemented Ms Q experienced a cardiac arrest and could not be revived.

An autopsy concluded the cause of Ms Q’s death was acute myocardial infarction (AMI) caused by coronary artery atherosclerosis. The pathologist considered the nausea and vomiting Ms Q experienced were symptoms of the evolving MI.

The hospital acknowledged that MI had not been considered, tested for or identified. However it noted the huge challenge in emergency medicine of diagnosing an atypical presentation. This was compounded where there were other explanations for a patient’s symptoms. In this case, Ms Q’s history of recent trauma, adverse reaction to opioids, and her explanation that appeared to rule out a medical episode as the cause of the fall were complicating factors.

The coroner accepted the clinicians’ diagnosis had been reasonable and their care appropriate.

The coroner noted the risk that results of an initial rapid assessment may potentially bias a later, more comprehensive assessment. However there was no indication of bias in this case.

The coroner recommended Ms Q’s case be used as a case study to highlight:

• the need to consider acute coronary syndrome as a possible diagnosis in females who may present atypically
• the importance of comprehensive primary and secondary assessments.

Atypical presentations will inevitably be challenging to diagnose. Signs and symptoms don’t always follow textbook patterns, and factors such as age, gender or ethnicity can influence how patients present. It is important to be aware of these variations.   

Differential diagnosis is an important part of clinical decision making even when symptoms may have a ready explanation.  Taking a moment to consider alternative explanations by asking:

- What else could explain these symptoms?

- What happens if I’m wrong?

- Would my treatment or management change with a different diagnosis? 

- Are there further tests that could confirm or rule out my diagnosis? 

When providing a second opinion be mindful of confirmation bias.  It is easy to be influenced by an existing diagnosis, particularly if a colleague has already assessed the patient.  Even if a second opinion aligns with the initial diagnosis, it’s essential to ensure that the conclusion was reached through independent, critical evaluation rather than passive acceptance.

Factsheet: Missed or delayed diagnosis

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