Metropolol during AMI reduces infarct size

[Summit]

https://www.nature.com/articles/ncomms14780

Early metoprolol administration during AMI, given as an adjunct to mechanical reperfusion has been shown to reduce infarct size and ameliorate post-infarction severe cardiac dysfunction11,38. Defining the mechanisms underlying this cardioprotection is therefore of great medical relevance since more efficient and specific protective strategies could be identified.

The ability of ADRB1 selective blockers to reduce infarct size was tested decades ago in several clinical trials, but the results were inconclusive1. However, most of these early studies were performed in the context of non-reperfused AMI. The advent of reperfusion as the treatment of choice for AMI changed the mode of myocardial death: from unrelieved ischaemia to a combination of ischaemia and reperfusion processes. Therefore the potential cardioprotective effects of ADRB1 selective blockers needed to be revisited in light of the current evidence of IR injury during AMI (ref. 1). The ability of metoprolol to reduce infarct size in the context of reperfused AMI was recently evaluated in the METOCARD-CNIC trial. In this trial, early i.v. metoprolol administration during ongoing AMI resulted in a significant reduction of infarct size9,39, and also significantly reduced the incidence of severe ventricular dysfunction and heart failure readmissions10.

And they showed that the mechanism was reducing inflammatory effects: "stunning" neutrophils so they did less damage on re-perfusion. (metop dose they used was 15mg IVP within 6 hours of AMI)