This study is looking at how a medication called beta-blockers (metoprolol) affects patients with a heart attack (STEMI) who are in the cardiac intensive care unit.

When patients are admitted to the unit, they will be randomly placed in one of two groups. One group will get the metoprolol medication, and the other will receive a placebo (a harmless pill that looks like the real medication). All other treatments will be the same for both groups.

During the study, which is 72 hours long, patients will be monitored for blood pressure, heart rate, and lactate levels alterations.

The main goal is to see if the medication helps improve patients condition or prevent it from getting worse. patients safety is a top priority, and if needed, the doctors can stop the study at any time if there are concerns.

A prospective, randomized, double-blind cohort study will be conducted on patients with STEMI who are hospitalized in the cardiac intensive care unit and classified as SCAI B at the time of admission by the attending physician. Patients will be identified upon admission to the unit and randomized into two arms - a control group and an intervention group. Randomization will be performed using sealed envelopes. A block randomization model will be used based on LVEF estimation of >40% or ≤40%.

In the intervention group, patients will receive standard beta-blocker treatment, specifically low-dose metoprolol at 25 mg twice daily. In the control group, patients will receive a placebo. All other standard treatments will be identical between the two study groups, in accordance with the unit's treatment protocol and the clinical status of the patients.

As an integral part of this treatment, patients will be continuously monitored for parameters including blood pressure, heart rhythm, and blood lactate levels.

The treatment duration under this protocol will be 72 hours or until the occurrence of the primary outcome, whichever comes first. The primary outcome is defined as progression of the patient's condition to SCAI C, according to accepted criteria, including an increase in lactate levels, a decrease in urine output, or a change in mental status. Per guidelines, every 24 hours, investigators will re-evaluate each patient. If they meet current criteria for beta-blocker administration (SCAI A status and no contraindications), the study drug will be terminated and active metoprolol will be prescribed.

To ensure patient safety, the treating staff will have the option to request unblinding of the patient's allocation at any time. Additionally, after the enrollment of 100 patients (or after one year, whichever comes first), an interim analysis of the data will be conducted to ensure the study remains within established safety parameters.

An echocardiogram and follow-up visit will be performed at 30 days.

Inclusion Criteria:

• Diagnosis of ST-segment elevation myocardial infarction (STEMI) confirmed by ECG, clinical signs, and coronary catheterization.
• Post-catheterization patients classified as SCAI B upon admission to the unit, defined by the presence of tachycardia and/or hypotension without signs of hypoperfusion (i.e., normal lactate levels, normal capillary refill, preserved mental status, and adequate urine output >0.5 mL/kg/hour).
• Age 18 years or older.
• Mentally competent to provide informed consent, understand the study procedures, and comply with medical recommendations.

Exclusion Criteria:

• Pregnancy.
• Inability to provide informed consent.
• Evidence of pulmonary edema.
• Bradycardia (heart rate <60 beats per minute).
• PR interval >240 milliseconds.
• Second- or third-degree atrioventricular (AV) block.
• Active asthma.
• Known hypersensitivity to metoprolol.

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