Why is a beta blocker (beta-adrenergic blocking agent) added post Non-ST-Elevation Myocardial Infarction (NSTEMI) with mild hypertension and Left Ventricular Ejection Fraction (LVEF) of 50%?

From the Guidelines

Beta blockers should be added post Non-ST-Elevation Myocardial Infarction (NSTEMI) with mild hypertension and Left Ventricular Ejection Fraction (LVEF) of 50% to reduce myocardial oxygen demand and prevent recurrent ischemic events, as they have been shown to decrease mortality by 23% in long-term trials 1. The primary mechanism of action of beta blockers is to block beta-adrenergic receptors, which reduces heart rate, blood pressure, and myocardial contractility, thereby decreasing myocardial oxygen consumption.

• Common beta blockers used include metoprolol, carvedilol, or bisoprolol, which should be initiated within 24 hours of admission if there are no contraindications such as cardiogenic shock, severe bradycardia, high-degree heart block, or severe bronchospastic disease.
• The dose should be titrated gradually to achieve a target heart rate of 55-60 beats per minute while maintaining adequate blood pressure.
• Beta blockers are typically continued indefinitely after NSTEMI unless contraindications develop, as they have been shown to reduce the risk of recurrent ischemia, ventricular arrhythmias, and mortality 1. It is advisable to use beta blockers without intrinsic sympathomimetic activity, and in patients with MI complicated with systolic cardiomyopathy with or without heart failure, one of the three proven beta blockers should be used: carvedilol, sustained-release metoprolol succinate, or bisoprolol 1.
• The American College of Cardiology Foundation/American Heart Association (ACCF/AHA) guidelines recommend a 3-year treatment course with beta blockers for patients with uncomplicated MI, but many patients with hypertension or heart failure/systolic cardiomyopathy are usually continued on an oral beta blocker indefinitely 1.

From the FDA Drug Label

DOSAGE & ADMINISTRATION SECTION Carvedilol Tablet should be taken with food to slow the rate of absorption and reduce the incidence of orthostatic effects. 2. 2 Left Ventricular Dysfunction Following Myocardial Infarction DOSAGE MUST BE INDIVIDUALIZED AND MONITORED DURING UP-TITRATION. Treatment with Carvedilol Tablet may be started as an inpatient or outpatient and should be started after the patient is hemodynamically stable and fluid retention has been minimized.

The beta blocker (beta-adrenergic blocking agent) carvedilol is added post Non-ST-Elevation Myocardial Infarction (NSTEMI) with mild hypertension and Left Ventricular Ejection Fraction (LVEF) of 50% to manage left ventricular dysfunction.

• The primary goal is to improve survival and reduce morbidity in patients with left ventricular dysfunction following myocardial infarction.
• Dosing must be individualized and monitored during up-titration.
• Treatment should be started after the patient is hemodynamically stable and fluid retention has been minimized 2.

From the Research

Rationale for Beta Blocker Use Post NSTEMI

• The use of beta blockers in patients with Non-ST-Elevation Myocardial Infarction (NSTEMI) is supported by several studies, including 3 and 4, which demonstrate a reduction in mortality and improved clinical outcomes.
• A study published in 4 found that early use of beta blockers in patients with NSTEMI was associated with lower in-hospital mortality and improved clinical outcomes, including a reduced risk of major adverse cardiovascular events.
• Another study 3 found that patients with NSTEMI and reduced left ventricular ejection fraction (LVEF) had higher mortality rates, but treatment with guideline-recommended medications, including beta blockers, was associated with a better prognosis.

Considerations for Patients with Mild Hypertension and LVEF of 50%

• A study published in 5 found that discontinuing beta blockers within 12 months after acute coronary syndromes (ACS) with LVEF ≥40% was not associated with an increased risk of major adverse cardiovascular events (MACE) compared to long-term beta blocker therapy.
• However, subgroup analysis suggested a potential risk in patients with ST-elevation myocardial infarction (STEMI), whereas there was no interaction with LVEF, suggesting that beta blocker discontinuation may be safe in patients with NSTEMI and preserved LVEF.
• The use of beta blockers in patients with mild hypertension and LVEF of 50% is supported by the findings of 3 and 4, which demonstrate a reduction in mortality and improved clinical outcomes in patients with NSTEMI.

Comparison with Other Therapies

• A study published in 6 compared the use of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) in patients with NSTEMI and preserved left ventricular systolic function, and found that ACEIs were associated with a lower risk of major adverse cardiac events (MACEs) compared to ARBs.
• Another study 7 found that multivessel percutaneous coronary intervention (PCI) was associated with a lower risk of MACEs compared to infarct-related artery (IRA)-only PCI in patients with NSTEMI and severe left ventricular systolic dysfunction.