Beta Blockers in the presence of AMI

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Handsome Robb

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Alright so I've asked a few people and decided I might as well make a thread rather than galavanting around in other people's threads.

We recently added Metoprolol to our STEMI protocol. It's 5 mg IV x1 for STEMIs presenting with SBP >140 and HR >100.

I think I have a handle on the science with that being the Metoprolol slows the rate which inherently lowers the cardiac output which in turn lowers afterload. The slowed rate and reduced afterload reduces myocardial workload and oxygen demand thus ultimately slowing the infarction. Please correct me if I'm wrong.

I haven't been able to find a whole lot of information on the whole concept as far as it's efficacy. It makes sense on paper but of course me being me I want to know if it's true in practice.

Another member brought up the good point that there is a risk of cardiogenic shock which seems like in combo with the nitro the risk is increased since cardiac function has already been compromised. It seems like you would only move to the Metoprolol after nitroglycerine but I haven't been able to get a straight answer as to concurrent vs. after NTG if the BP and HR maintained above the 140 systolic and 100 bpm rate.

Anyone else giving Beta Blockers in the presence of a STEMI?

Anyone have any input or references they could steer me towards? My googlefu is not strong tonight. I've gotten references to the COMMIT study but it seems that it only looked at Plavix not beta blockers but I also suck at reading studies seeing as I have no background in statistics.

Edited to make my grammar not suck.
 
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NVRob said:
Another member brought up the good point that there is a risk of cardiogenic shock which seems like in combo with the nitro the risk is increased since cardiac function has already been compromised. It seems like you would only move to the Metoprolol after nitroglycerine but I haven't been able to get a straight answer as to concurrent vs. after NTG if the BP and HR maintained above the 140 systolic and 100 bpm rate.

Anyone else giving Beta Blockers in the presence of a STEMI?

Anyone have any input or references they could steer me towards? My googlefu is not strong tonight.
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Interesting, I didn't even think about the possibility for cardiogenic shock when we were discussing it. I suppose that does make sense though.

Anyways, as you already know, I don't actually have an answer for you...so I'll be interested in seeing what people come up with.
 
You also have to consider as long as a patient remains tachycardic or even relatively tachycardic it decreases cardiac perfusion time. So the slower the rate the longer the diastolic period and greater cardiac perfusion time. Thats why even though morphine doesnt decrease preload and after load the way it has been thought for decades what it does do well is decrease the patients anxiety and HR in return as long as there is no other reason for the tachycardia
 
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Obviously there are some contraindications... hemodynamic collapse/hypotension, heart block beyond first degree, severe bradycardia, active bronchospasm, cocaine induced MI, etc...

In the absence of those, the strongest evidence is for initiation of oral beta blockers within the first 24hrs (Grade 1A). And though not quite as strong there is a Grade 2B recommendation for IV beta blocker for hypertensive patients on presentation.

In the COMMIT/CCS2 trial there was no overall mortality benefit from early IV beta blockers. But if you took the patient's presenting hemodynamics into consideration, then there was a trend toward benefit in those hemodynamically stable vs increased mortality in those compromised.

Having to look through some studies here, but looks an analysis of the CADILLAC trial showed a lower mortality in those who had received a pre-PCI beta blocker, though this was limited to those not previously on a beta blocker.

And like was mentioned there several potential physiological benefits: decreased oxygen demand, increased coronary perfusion, reduction in remodeling, improved diastolic function, and decreased risk of vfib.

Anyone know of any trials specifically looking at prehospital beta blockers?

As long as no contraindications exist and depending on transport time then certainly reasonable for EMS to initiate IV beta blocker therapy.

Chances are the pt is going to receive nitro first because of ease of administration, but also how the patient presents and vitals would play a role. If they present tachycardic, hypertensive, or even rapid afib then certainly reasonable to look at getting beta blocker on board early as just controlling rate and BP may stabilize things a bit.

I actually don't know if our county EMS has IV beta blockers in their protocol. Transport times here are so short with multiple primary PCI centers so if not given via EMS the pt will most likely get a beta blocker 5-10min later in the ED.
 
in COMMIT, pts. with systolic BP between 120 and 160, and pts. with a HR between 70 and 90 showed a mortality benefit from metoprolol. All patient groups had increased risk of cardiogenic shock, which was higher than mortality benefit. When they looked at a composite end point of death and shock, only the subset of pts with a HR of 70-90 was there a benefit. For BP, there was no benefit (and a lot of harm) for pts with BPs <120. The benefit was highest for pts with BPs between 120 and 140 and decreased with ea. group with a higher BP.

http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(05)67661-1/fulltext
 
I don't know how fast you push your metoprolol, however, I'd caution against slamming in 5mg. Give it 1mg at a time, and wait 2-3 minutes before giving more. Sometimes just 1mg is enough to push you in the direction you want to be going and 5mg will knock you down into the 40's.
 
Thanks guys, all very good information. I'm all ears for more.

Corky, definitely something I hadn't considered but now that you bring it up makes sense.

FLdoc, thanks for the reference, I will have to check out the CADILLAC trial.

Medicsb thanks for the link!

Jwk, I've never personally given it and no specific time was outlined it just states "5 mg Metoprolol IV". I definitely wouldn't slam it, until you brought this up I was thinking along the lines of 5 mg/2-5 minutes.
 
Metoprolol is in our Virginia protocols for up to 15mgs.

Indications per protocol are: confirmed MI on 12-lead or persistent chest pain after NTG and morphine with specified vital sign parameters SBP 120 and HR >80.
 
I've always been taught that beta blockers are cardioprotective in M.I, especially in complete occlusions. Helps blunt the reflex tachycardia from nitro (which won't benefit much in a complete occlusion), which is a slippery slope.
 
Doczilla said:
I've always been taught that beta blockers are cardioprotective in M.I, especially in complete occlusions. Helps blunt the reflex tachycardia from nitro (which won't benefit much in a complete occlusion), which is a slippery slope.
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The prevailing idea was that they were cardioprotective through decreased oxygen demand via decreased chronotropy, inotropy, and decreased arrythmogenicity. But, COMMIT has raised huge new questions about whether or not that is true. It could be true that it is protective in some patients, but as of now, how do we know who those patients are, if they exist at all?
 
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