By John Pickering 31/08/2016 2


This week the NZ Herald published an article saying doctors are failing to spot heart attacks in thousands of women.  This sounds alarming, could it be happening in NZ? Are women getting a raw deal?

Important questions.  This post looks at the study behind the media and then at how heart attacks are being diagnosed in New Zealand.

The Herald article is evidently based on press releases related to a study published to coincide with the European Society of Cardiologist’s conference currently underway in Rome and attended by some 30,000 cardiologists, other physicians, industry types, and the Pope (yep!). The study in question comes from the University of Leeds. Here’s the Leeds Uni press release.

The US red-dress logo which is their national symbol for women and heart disease
The US red-dress logo which is their national symbol for women and heart disease

The study

The study is based on an audit of UK data collected about patients between 2004 and 2013 whose final diagnosis was a heart attack (in clinical jargon a myocardial infarction, either STEMI or NSTEMI).  The full article is available here.

The subjects were patients who at discharge from hospital had a heart attack diagnosis.  The authors looked at the preliminary diagnosis of patients when they first entered the hospital and compared that diagnosis to the final diagnosis of a heart attack.  The preliminary diagnosis was for about a 30% of patients not explicitly a heart attack – ie often something like “chest pain of uncertain cause.”  In the press release and news reports this was reported as a “misdiagnosis.”

Point 1:  The term “misdiagnosis” is inappropriately applied here.  While some forms of heart-attacks can be diagnosed in the ED, most can not.  Indeed, the guidelines for diagnosis of a heart attack require some blood measurements at least 6 hours apart.  Nowadays, the later blood sample is not done in the ED, but in a cardiology or general medicine ward.  That is, the ED physicians often don’t have all the data to make a definitive diagnosis – hence only a preliminary diagnosis is made. Most of the time the job of the Emergency department physicians is to rule-out some possible diagnoses and to identify patients at significant risk of a heart attack.  These patients are referred on to the specialist teams within the hospital who make the final diagnosis.*  Yesterday I was speaking with a cardiologist who was explaining how often cardiologists themselves disagreed over a diagnosis.  It ain’t easy.

The press releases and media reports emphasise that a larger proportion of women than men were likely to have a change between the preliminary and final diagnosis.  The Leeds University press release states women were 59% for a final STEMI diagnosis and 41% for a final NSTEMI diagnosis more likely than men to have a change from the preliminary diagnosis.

Point 2:  These numbers are not reported in the published paper!  Nor is anything about the differences between men and women discussed in the paper.  In the results section it is simply stated that those who had an initial diagnosis that changed were more likely to be older, female, and have a co-morbidity. There are some numbers related to this in a table. In the table I note that patients older than 61 compared with younger patients had at least (more if they were even older) the same odds of having a diagnosis changed as did females compared with males (it’s a little awkward in the paper because the odds ratio is written the opposite way around – but this can be rectified simply by taking the reciprocal of the odds ratio and comparing that).  There were also other predictors of a change in diagnosis (eg higher heart rate).  The cynic in me thinks that it may be for publicity reasons that the emphasis has been placed on the sex differences in press releases.

Point 3: What is important about the study is that in those who had a change in diagnosis the one-year mortality rates were higher.  While the suggestion is made that this is because of delay in time to treatment (known from other studies to be important), there are other potential reasons because of the differences in demographics and co-morbidities between the groups.

New Zealand

The study began at a time when the blood biomarkers indicative of a heart attack that are used now (troponins) were not in common use.  There have been several generations of markers, the latest of which are “high-sensitivity troponins.”  The authors’ recommended that:

“…our results… call for the earlier use and wider adoption of high sensitivity troponins as well as a focus on the systematic application of accelerated diagnostic protocols using risk scores rather than subjective clinical assessment.”

The good news is that New Zealand is now the only country in the world** to have accelerated diagnostic protocols using risk scores in place in every ED.  Furthermore, most ED’s are using the latest high sensitivity troponins.

In the Christchurch ED, different sex-specific thresholds of the troponin used for risk stratifying and diagnosing heart attacks are used.  This is because in the general healthy population males have slightly higher values of these troponin measurements than females.  Therefore, to avoid underdiagnoses of females a lower diagnostic threshold is used.  Furthermore, in a study we were part of and lead by our Brisbane based colleagues, using sex-specific threshold helped improvs risk prediction for future adverse events in women.

Conclusion

In New Zealand it is less likely that women are getting a raw deal.

*perhaps the Pope a.k.a @Pontifix [literally the “bridge builder”] could help bridge the divide between ED physicians and cardiologists – generally ED physicians rule-out heart attacks, Cardiologists rule-in heart attacks.

** although Queensland also has this and they like to think of themselves as a country sometimes


2 Responses to “Heart attacks in NZ – are women getting a raw deal?”

  • Thanks for this, Dr. Pickering. New Zealand women are fortunate indeed to have available to them what appears to be both cutting edge cardiac enzyme diagnostic tools as well as practice guidelines that are appropriately followed.

    As you say, regional differences in such advances exist in Emergency Medicine and Cardiology depending on where you happen to live in the world during your heart attack – for example, the puzzling reluctance in many U.S. hospitals to adopt, respectively, things like high sensitivity blood tests for troponins or radial access PCI.

    Here in Canada (where incidentally, high-sensitivity troponins are now widely used), the word “misdiagnosis” is entirely appropriate when, instead of a correct MI diagnosis/referral to a cardiologist, female patients are still being sent home with inaccurate diagnoses ranging from GERD to stress, gall bladder issues or anxiety (a terrific all-purpose cardiac misdiagnosis in women, by the way). Some studies have blamed these misdiagnoses on women’s higher likelihood of presenting with atypical cardiac symptoms. We know, for example, that 40% of women experience no chest symptoms at all during MI (Canto et al, 2012). How then do NZ Emergency personnel decide if the woman in mid-heart attack presenting with just vague shoulder pain or fatigue should have her cardiac enzymes tested, just in case?

    When MI symptoms do not reflect the Hollywood Heart Attack, it remains up to the ED physician’s discretion to determine who gets referred to cardiology or not, or even who gets cardiac tests or not. Even with textbook MI symptoms like my own (central chest pain, nausea, sweating, pain down my left arm), I was back at home well within a few hours of the onset of symptoms, all cardiac test results “normal”, no cardiologist called in, confidently misdiagnosed (“YOU are in the right demographic for acid reflux!”) and feeling very, very embarrassed for having made a fuss over “nothing”. And we know from a growing number of studies on treatment-seeking delay behaviour in female heart attack survivors that, as you point out as well, such delay does indeed impact our outcomes and can certainly influence patient decision to seek further treatment. When my cardiac symptoms later returned (of course they did!), there was no way I was going to embarrass myself once again by going back to that ED – because a man with the letters M.D. after his name had told me quite confidently: “It is NOT your heart.”

    The reality does seem to remain that too often here in Canada (and certainly in the U.S. as well), getting past the ED gatekeepers can still be the most treacherous part of surviving an MI if you’re female.
    regards,
    C.

    • Thanks for the comment Carolyn – fascinating to hear what is happening in Canada. Anyone being sent home inappropriately is a problem (the paper, though, did not look at this – merely at the cohort who were referred from ED and ended up with an MI diagnosis). You asked about NZ – quite recently all NZ EDs have gone to an evidence based accelerated diagnostic protocol involving serial troponins in the ED, ECG, and a risk assessment score (mainly EDACS, some TIMI). Both research data and prelim data from the implementation suggests that there is a v v low rate of people being sent home who are returning within a month with a diagnosis of MI.
      One of the incidental findings from data before the implementation of the ADPs was that there was as large a proportion of patients having only a single troponin measure as having two. Possibly, this is because it is standard practice for a nurse who takes the first blood sample to order trops on anyone with even a hint they may be having a heart attack (ie often even before a patient is seen by a doc).
      Another factor of implementing ADPs throughout the country is that this entailed getting ED physicians, cardiologists, nurses, Gen med, and management in a room together at each hospital to work out how their processes were going to work. I attended a couple of those meetings and was impressed by the desire to be evidence based, yet erring on the side of caution. As an “outsider looking in” I have found the different thinking of ED staff and cardiologists fascinating (obviously I oversimplified things in the blog post as you quite rightly pointed out).

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