Adjunctive Therapies

1. Morphine

Usage: Used if chest pain is not relieved by nitroglycerin.

Clinical Considerations:

• Administered in doses of 2-4 mg IV, repeat as needed for pain control.
• Use judiciously as it can delay the absorption of oral antiplatelet agents, particularly P2Y12 inhibitors.
• Recent observational data suggest potential harm with morphine use in ACS, including increased mortality and recurrent ischemic events, although these findings need further confirmation in randomized trials.

Clinical Pearls:

• Pain Relief: Effective for managing severe pain and anxiety in ACS patients.
• Respiratory Depression: Monitor for potential respiratory depression and hypotension.
• Absorption Delay: Be cautious of delayed absorption of P2Y12 inhibitors, which may affect antiplatelet efficacy.
• Observational Study Findings: A meta-analysis involving 64,323 patients indicated a higher incidence of recurrent MI with morphine use (3.7% vs. 2.9%), though no significant difference in all-cause mortality was observed (Heart Asia) (BMJ Open). The EARLY ACS trial subanalysis showed that morphine use in patients pretreated with clopidogrel was associated with higher rates of composite ischemic events at 96 hours (American College of Cardiology).

Guideline Recommendations:

ACC/AHA Guidelines: Morphine can be used for chest pain relief in patients with ACS, but its use should be cautious and limited to situations where nitroglycerin is insufficient (Class IIb, Level of Evidence C).

References: Amsterdam EA, et al. Circulation. 2014;130(25)

2. Oxygen

Usage: Administer oxygen only if O2 saturations are less than 90%.

Clinical Considerations:

• Routine use of supplemental oxygen in patients with ACS without hypoxemia (O2 saturations ≥90%) is not recommended.

Clinical Pearls:

• Hypoxemia: Oxygen is beneficial for patients with hypoxemia (O2 saturation <90%), heart failure, or dyspnea.
• Prophylactic Use: No data supports the prophylactic use of oxygen supplementation in ACS patients with normal oxygen levels.

Guideline Recommendations:

ACC/AHA Guidelines: Oxygen should be administered to patients with hypoxemia, respiratory distress, or other high-risk features (Class I, Level of Evidence C).

References: Amsterdam EA, et al. Circulation. 2014;130(25)

3. Nitroglycerin

Usage: Used for immediate relief of ischemic chest pain. Typically given sublingually as a 0.4 mg tablet or spray. If pain persists, intravenous nitroglycerin can be considered.

Clinical Considerations:

• Administer sublingually every 5 minutes up to 3 doses for chest pain relief.
• IV nitroglycerin can be used if pain persists or in cases of hypertension or heart failure.
• Caution in patients with inferior STEMI due to preload dependence and those with recent PDE-5 inhibitor use.

Clinical Pearls:

• Pain Relief: Provides rapid relief of ischemic chest pain.
• Hypotension Risk: Monitor for hypotension, particularly in patients with inferior MI or volume depletion.
• Preload Dependence: Avoid in patients with right ventricular infarction due to the risk of severe hypotension.

Guideline Recommendations:

ACC/AHA Guidelines: Recommended for patients with ongoing ischemic discomfort, heart failure, or hypertension (Class I, Level of Evidence B).

References: O’Gara PT, et al. Circulation. 2013;127(4)

4. Beta-Blockers

Usage:

• Consider IV beta-blockers if no signs of heart failure or shock are present within 24 hours.
• Start oral beta-blockers within 24 hours if no contraindications exist.

Clinical Considerations:

• Administer oral beta-blockers within the first 24 hours unless contraindicated by heart failure, low output state, or risk of cardiogenic shock.
• IV beta-blockers can be considered in hypertensive patients without signs of heart failure or shock.

Clinical Pearls:

• Mortality Reduction: Beta-blockers reduce mortality and reinfarction rates in ACS patients.
• Contraindications: Avoid in patients with signs of heart failure, low output state, or risk for cardiogenic shock.
• Early Initiation: Early administration is associated with better outcomes but must be balanced against potential risks.

Guideline Recommendations:

ACC/AHA Guidelines: Oral beta-blockers should be started within 24 hours for all patients without contraindications (Class I, Level of Evidence A). IV beta-blockers may be considered in certain cases (Class IIa, Level of Evidence B).

References: Amsterdam EA, et al. Circulation. 2014;130(25)

Historical Perspective: MONA-B Learning Mnemonic

The mnemonic “MONA-B” stands for Morphine, Oxygen, Nitroglycerin, and Aspirin, with Beta-blockers often included. This mnemonic has historically been used to help healthcare providers remember the key initial treatments for ACS.

• Morphine: Historically used for its analgesic effects and to reduce anxiety and myocardial oxygen demand. However, recent studies have raised concerns about its potential harm in ACS patients.
• Oxygen: Traditionally administered to all ACS patients, but recent evidence suggests its use should be limited to those with hypoxemia (O2 saturation <90%).
• Nitroglycerin: Long used to provide rapid relief of ischemic chest pain by dilating coronary arteries and reducing myocardial oxygen demand.
• Aspirin: A cornerstone of ACS management, it rapidly inhibits platelet aggregation and reduces the risk of further thrombotic events.
• Beta-blockers: Used to reduce myocardial oxygen demand, lower heart rate, and reduce blood pressure, contributing to decreased mortality and reinfarction rates.

Reperfusion Therapy for ACS

Reperfusion therapy is a cornerstone of treatment for patients with Acute Coronary Syndrome (ACS), particularly those with ST-segment elevation myocardial infarction (STEMI). The approach varies between STEMI, Non-ST-segment Elevation Myocardial Infarction (NSTEMI), and Unstable Angina (UA).

1. STEMI (ST-Segment Elevation Myocardial Infarction)

Primary Percutaneous Coronary Intervention (PCI):

• Preferred Method: PCI is the preferred reperfusion strategy if it can be performed within 90-120 minutes of first medical contact.
• Procedure: Involves mechanically opening the blocked coronary artery using a catheter-based approach, often with the placement of a stent.
• Clinical Pearls:
  • Timing: Aim to achieve door-to-balloon time within 90 minutes.
  • Advantages: PCI is associated with lower rates of reinfarction and stroke compared to fibrinolytic therapy.

Fibrinolytic Therapy:

• Indication: Considered when primary PCI is not available or cannot be performed within 120 minutes.
• Agents and Dosing:
  • Alteplase (t-PA):
    • Total dose should not exceed 100 mg.
    • 15 mg IV bolus, then 0.75 mg/kg (up to 50 mg) over 30 minutes, followed by 0.5 mg/kg (up to 35 mg) over 60 minutes.
  • Reteplase (r-PA):
    • Two IV bolus injections of 10 units each, 30 minutes apart.
  • Tenecteplase (TNK-tPA):
    • Weight-based dosing as a single IV bolus over 5 seconds:
    • <60 kg: 30 mg
    • 60 to <70 kg: 35 mg
    • 70 to <80 kg: 40 mg
    • 80 to <90 kg: 45 mg
    • ≥90 kg: 50 mg
• Clinical Pearls:
  • Time Sensitivity: Administer within 30 minutes of hospital arrival when PCI is not feasible.
  • Bleeding Risk: Monitor for increased risk of bleeding, including intracranial hemorrhage.

Guideline Recommendations:

ACC/AHA Guidelines: Recommend primary PCI as the preferred method for reperfusion therapy in STEMI, with fibrinolytic therapy as an alternative when PCI is not available within the recommended time frame (Class I, Level of Evidence A).

2. NSTEMI (Non-ST-Segment Elevation Myocardial Infarction) and UA (Unstable Angina)

Early Invasive Strategy:

• Indication: Recommended for high-risk patients (e.g., those with positive biomarkers, dynamic ST changes, or hemodynamic instability).
• Procedure: Diagnostic angiography with intent for revascularization (PCI or CABG) within 24-48 hours.
• Clinical Pearls:
  • Risk Stratification: Use risk scores such as TIMI or GRACE to guide decision-making.
  • Antithrombotic Therapy: Administer antiplatelet agents (e.g., aspirin, P2Y12 inhibitors) and anticoagulants (e.g., UFH, enoxaparin, bivalirudin) before the procedure.

Conservative Strategy:

• Indication: Considered for low-risk patients or those with contraindications to invasive procedures.
• Management: Optimize medical therapy, including antiplatelet agents, anticoagulants, beta-blockers, statins, and ACE inhibitors.
• Clinical Pearls:
  • Monitoring: Regularly reassess for any changes in clinical status that might necessitate invasive evaluation.
  • Medication Adherence: Ensure patients adhere to prescribed medications to manage symptoms and prevent progression.

Guideline Recommendations:

ACC/AHA Guidelines: Recommend an early invasive