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Monday, December 24, 2012

Gender, EMS, and STEMI - new study

Does our care of the patient change when the patient is a woman?

If you're like most EMS providers, your response is a strong "no." People who go into EMS generally share strong ideals, and are motivated to provide the best care possible to everyone who needs it. 

With that in mind, though, a recent study found results that are difficult to explain, and ought to prompt us to reflect on our practices. It's not proof, but it deserves discussion.

Is on-scene time longer for women with chest pain?
Time is muscle - you know the drill. With chest pain, and especially in a STEMI, we have the ability to save lives. This is what EMS is for; we identify the sick person, and we get them to the right place, fast.

Too fast! (jk - no injuries.)
With all the emphasis on reducing the door-to-ballon time, we have to identify any reasons that would delay definitive care. What if being female is one of those reasons? 

The authors of Gender differences in scene time, transport time, and total scene to hospital arrival time determined by the use of a prehospital electrocardiogram in patients with complaint of chest pain. (PDF link) looked at the EMS service in San Diego, and analyzed run-forms of chest-pain patients. They looked at two time periods, before & after EMS started obtaining prehospital ECGs. They then looked at the various time intervals, as well as the computer interpretations of STEMI (a required element in their system for field-activation of the cath lab).

They found over 21,000 patients who had been transported for chest pain. About half of the patients were men, but the women were, on average, significantly older (65 vs 59 years of age). Only 3% of the patients (in the later time period) had a STEMI, with most of those being men.

When they looked at the scene times and transport times for chest pain patients, nothing changed between the two time periods overall. In the second period, however, they found that patients with a "STEMI" interpretation on the ECG had shorter scene and transport times.

It gets more interesting, however, when they broke things down by gender. It seems that that women had longer scene times than men, both for those with and without a STEMI. Specifically, women with a STEMI, on average, had scene times about 3 minutes longer than men, while women with chest pain (but no STEMI) had scene times about a 1.5 minutes longer than men. Transport times were the same, roughly, for men and women.

This is a small, but provocative result, and it isn't clear what it demonstrates, let alone proves. 

Did paramedics feel less "urgency" with the female chest-pain patients? This seems unlikely, since the actual transport times were similar. Everyone got driven to the ED at the same speed.

The study design can't answer what accounted for the difference in scene time interval, unfortunately. The generally older age of the female patients could suggest that evaluation was more complex, and accordingly required more time. It's already well-known from other studies that women with ACS generally have more comorbid conditions (such as hypertension and diabetes) than men.And it's also hard to interview older patients quickly; some things are hard to rush.

Lastly, the difference is small in absolute terms. Although the authors suggest that the difference in scene time for STEMI could result in a 0.25% - 1.6% increased mortality, this is based on a questionable extrapolation.

How does this fit with prior studies?
It is still possible that there is bias in the care of female patients that was not captured in the data here. A prior EMS study showed that 7.5% fewer women than men got ECGs for chest pain (Is there gender bias in the prehospital management of patients with acute chest pain?). We don't know if this was the case in the current study, since the authors "assumed that all patients," men or women, got ECGs, since "it was the protocol." Some basic QA about ECG completion rates, by gender, would have strengthened the study.

Another study examined the differences in prehospital intervals  among men & women who ended up being diagnosed with an MI. The authors of Myocardial Infarction: Sex Differences in Symptoms Reported to Emergency Dispatch also found that women had longer on-scene times, by about 1 minute. When they took age into account, whoever, that difference disappeared. Hopefully the next San Diego EMS study will obtain the data to make these sorts of adjustments.

The Bottom Line
Like all studies that are able to "dredge" through a large data-base of run-forms, we end up with more questions than answers. The large number of patients enables researchers to find some statistical results, but the interpretation gets muddy.

Moving forward, the key will probably be in QA; making sure that all the appropriate patients get ECGs, that transport is expedited in STEMI, and that feedback is obtained from the ED and cardiology. I'm hoping that future, and better, studies will demonstrate that EMS is taking acre of everyone to the same high standards. 


  1. I think I can definitively say that the logistics behind running a 12-lead on a female patient are a heck of a lot more difficult in the prehospital environment. On almost any male patient I can remove or roll up their shirt and begin setting up an ECG within 15 seconds of patient contact if I want to. When I'm working with a female patient, especially during winter in the northeast, I spend time both explaining the procedure and figuring out how I'm going to snake the wires over, under, and through their clothing to make sure I get a clean and accurate tracing while still maintaining their privacy. I doubt it accounts for all of the extra time noted in this study, but I'm pretty confident that it's part of it.

    1. Since the population was a) in San Diego, and b) older folks, I wouldn't say that's a slam-dunk.

      But it's a compelling thought. How would you design the study protocol? Chicago vs Miami? Female EMTs vs male? Logistic regression against temperature?

  2. Once again you've prompted a post length comment which I turned into a post over at my place.

    Interesting topic, but I think they might be barking up the wrong coronary artery.

    To mix a metaphor.

    1. You make a lot of great observations, and I agree wholeheartedly with your main point:

      "Start by teaching that not all ACS events have chest pain and change protocols to reflect that. "

      Since the authors in this study did not account for age, it's entirely possible that difficult IV access accounted for the on-scene time. It would be difficult to study that prospectively, but perhaps they could look at # of IV attempts between men & women?

  3. I'll add another vote for Vince's theory; I'm much the same way- I take a moment or two to explain the procedure ad talk about where the "stickers" are going to go. Older women also often have more complicated clothing, regardless of season. With a male it's "I have to put some stickers on your chest, ok?" and up comes the shirt.

    Also of note, it's even worse in the ER environment. Female patents have to be taken to another room for a 12-lead, curtains drawn, etc. A male can just get their shirt pulled up right in Ambulance Triage.