The Theorem of Early STEMI Notification

I have been doing a lot of thinking about STEMI. I deal with it on the street as a paramedic and I deal with it at the hospital as an EMS Coordinator and member of our hospital’s door-to-balloon committee. Here is the progression I have seen over the last twenty years when it comes to STEMI Care:

1. Put patient on 3 lead monitor, IV, 02, ASA, NTG and Morphine
2. Do a 12-lead, in addition to the above. If it shows ST elevation tell nurse on arrival at hospital or find Dr and show him 12-lead.
3. If patient has inferior MI, do right sided 12-lead and withhold nitro if RVI
4. Mention STEMI on radio patch, and hope nurse tells doctor
5. Call in STEMI ALert and Ask to speak to Dr.
6. Use Fentanyl instead of Morphine.
6. Give 02 only if hypoxemic
7. Apply 12-lead immediately on patient contact, and if it shows STEMI, call in STEMI alert ASAP, ideally within 5 minutes of patient contact.

It is this last element involving Early Notification I want to talk about today. How much notification does a hospital need? For many years nearly every notification was a “we’re 2-3 out with a patient with etc. etc. etc, and I have done IV, 02, monitor, etc. etc. etc.”

Paramedics were uncomfortable patching in before they had done all their treatment. Why? Habit and perhaps because they didn’t want the doctor or nurse to say, how come no ASA? Or do you have an IV? We are telling them now we would like to hear a patch that says, “Hello, medical control. I have a STEMI Alert and am requesting cath lab activation. I’m on scene with a 50 year old male, cool and clammy with severe chest pain, father died at 49 of an MI. 12-lead shows 2 millimeters elevation in II, III, and avF with reciprocal change in I and avL I’ll get back to you with more once we’re transporting. Current ETA is 30 minutes.”

30 minutes. Is 30 minutes too much notification? In some cases, maybe. In others, typically on nights and weekends, it is probably just right.

Albert Einstein and Sir Issac Newton look out, but I have developed my own mathematical formula to determine how much notification is needed.

Early notification must be > or = to the amount of time it takes the cath lab to be ready to accept the patient to achieve optimal benefit.

Any less time is potential lost minutes, lost heart muscle.

How long does it take a cath lab to be ready? It depends. I did a back of the envelope study which showed an average time of 15 minutes, but with a range from one to 40. Most PCI centers have call-in teams for the evening and weekend hours who must be ready within 30 minutes. Sometimes during the week, even when the team is present, the cath lab tables are being used by elective patients. A 30 minute heads up on an incoming STEMI can mean an available table when the patient gets there that might not otherwise have been kept open.

In the ideal world of early notification, the cath lab is always ready when EMS arrives so that the patient can go right to the cath lab on the EMS stretcher.

Let’s do some math.

Let’s say on this day, it will take the cath lab 20 minutes to be ready.

EMS calls from 20 minutes out. Heart muscle saved = 20 minutes.
EMS calls from 15 minutes out. Heart muscle saved = 15 minutes
EMS calls from 10 minutes out. Heart muscle saves = 10 minutes.
EMS calls from 5 minutes out. Heart muscle saved = 5 minutes.

Now, I could complicate the formula by adding a plus time for time in ED(beyond mere waiting time). I believe that by its nature, transferring a patient to an ED bed, to an ED nurse, etc, adds a time tax that may add 5 minutes or more than if the patient had stayed on the EMS stretcher.

EMS calls from 20 minutes out. Heart muscle saved = 20 minutes.
EMS calls from 15 minutes out. Add 5 minute ED tax. Heart muscle saved = 10 minutes
EMS calls from 10 minutes out. Add 5 minute ED tax. Heart muscle saved = 5 minutes.
EMS calls from 5 minutes out. Add 5 minute ED tax. Heart muscle saved = 0 minutes.

The bottom line is if you call in 20 minutes out versus 10 minutes out, in this case, you are directly saving the patient 15 minutes of heart muscle.

EMS is the dispatcher for the cath lab. The patient with a STEMI needs the cath lab in the same way a patient in ventricular fibrillation needs a defibrillator or a patient in anaphylaxis needs epinephrine or a patient in penetrating trauma needs a surgeon. Yes, there are treatments you can do to help the patient, but unless he is in v-fib himself, none are more important than activating the cath lab. The quickest way to get the patient to the cath lab is to see that the cath lab is ready by the time the patient hits the hospital. In the ideal world, all stable STEMI patients (those with patent airways and normotensive vitals) could then bypass the ED and go right to the cath lab on EMS stretchers.

So remember:

Early notification must be > or = to the amount of time it takes the cath lab to be ready to accept the patient to achieve optimal benefit.

Greet ACS patient
Acquire a 12-lead
Unless patient goes into vfib (shock!), activate the cath lab
Proceed with treatment/transport

5.

4 Comments

  • Christopher says:

    Excellent points! We’re moving to earlier notifications for everything, even stubbed toes. I’ve anecdotally noticed 5-10 minutes in savings from beds being assigned earlier.

    As for, “[u]nless patient goes into vfib (shock!), activate the cath lab.” Still activate the cath lab! Let them deactivate themselves or the ED MD cancel them, but they really should be there upon your arrival.

    • medicscribe says:

      I should have been more clear here. What I meant was the only thing that should prevent you from immediately activating the cath lab is the need to push the shock button. Once you have pressed the button and shocked the patient, then you can give a heads up to the cath lab. If we have a known STEMI that goes into cardiac arrest, we will likely give a heads up that we are coming in with a STEMI. In our hospital, we once took a patient up to the cath lab while still doing CPR. If the patient is in refractory vfib, the cath lab may be the only hope. If a patient is in vfib in the field, but we don’t have a 12-lead showing the STEMI, we would not activate the cath lab until after ROSC, and then only if the 12-lead showed a STEMI. But in the hospital, it is becomming more common lately for patients with ROSC to go to the cath lab even if their 12-lead does not show a STEMI, if the doctors suspect a cardiac cause of the arrest.

  • Jason says:

    So I read something interesting a while back and unfortunately I’m not going to be able to site a source but it said this. A door to ballon time (d2b) of < 90 mins was immensely beneficial in decreasing m&m in STEMI pt's. We all know that now. It said a d2b < 75 mins added a little more benefit in reducing m&m. But I think at about d2b of about 60 mins we start to approach the limit. That is in decreasing d2b below 60 mins we realize no additional benefit.
    Can anyone site the study?

  • Jake says:

    As for, “[u]nless patient goes into vfib (shock!), activate the cath lab.” Still activate the cath lab!”

    I disagree, but only partially. Assuming by “vfib” we’re talking pulseless, then I would wait until getting ROSC before specifically activating the cath lab.

    *But* that is based on my squad’s practices: 1) codes are generally worked on-scene until either ROSC or termination; 2) while working a code, we normally contact our hospital with a “heads up”, especially when it’s a witnessed arrest. I would certainly include the STEMI information in that but I would let the ER make the decision on whether to activate the cath lab or not.

    Of course, the window where this could happen is also pretty narrow – we usually will call the STEMI alert within a minute or two of getting a STEMI positive 12-lead.

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