Drugs for STEMI - Chapter 56

Overview of ST-Elevation Myocardial Infarction (STEMI)

  • Myocardial Infarction (MI): Ischemia-induced necrosis of the myocardium.

  • STEMI Defined: Acute MI resulting from complete blockage of regional myocardial blood flow, indicated by ST segment elevation on ECG.

  • Differentiated from non-ST-elevation MI (NSTEMI), which involves partial blood flow obstruction.

Significance of ST Segment Changes

  • ST Elevation: Typically denotes heart muscle injury due to significant coronary artery blockage, indicating a risk of heart attacks (MIs).

  • ST Depression: Usually points to myocardial ischemia.

Pathophysiology of STEMI

  • Causes of STEMI:

    • Blocked blood flow due to platelet plugging and thrombus formation leading to myocardial injury and ventricular remodeling.

    • Progression associated with atherosclerosis: plaque build-up leading to narrowed or completely blocked coronary arteries.

  • Consequences: Lack of blood flow can result in heart attack, with symptom severity depending on damage extent and location.

Symptoms of STEMI

  • Typical Presentation:

    • Severe chest pain (substernal, crushing, radiating to arm/jaw).

    • Accompanying symptoms: sweating, weakness, sense of impending doom.

    • Note: 20% of patients may be asymptomatic.

  • Diagnostic Indicators:

    • Characteristic ECG changes (elevation of ST segment).

    • Biochemical markers: Cardiac troponin I, cardiac troponin T, and CK-MB enzyme.

Management Strategies for STEMI

  • Routine Drug Therapy:

    • Morphine: Pain relief and anxiety reduction.

    • Oxygen: Supplemental to improve oxygenation.

    • Nitroglycerin: Vasodilation to improve blood flow.

    • Aspirin: Essential for inhibiting platelet aggregation; advised to be chewed for rapid action.

    • Beta Blockers: Atenolol, Metoprolol to reduce heart workload and oxygen demand.

  • Reperfusion Therapy: Critical to restore blood flow.

    • Primary Percutaneous Coronary Intervention (PCI): Preferred method if performed shortly after symptom onset.

    • Fibrinolytic Therapy:

      • Medications: Alteplase (tPA), Reteplase, Tenecteplase.

      • Target: Initiate within 30 minutes of emergency department arrival for optimal effect (most effective within first 4-6 hours).

Goals of Therapy

  • Improve ventricular function, limit infarct size, and reduce mortality rates.

  • Successful timely administration results in opening occluded arteries in approximately 80% of patients.

Test-Taking Tips for Nurses

  • Aspirin Administration: Always instruct to chew the tablet for maximum benefit in a STEMI situation.

  • Recognizing Medication Protocols: Familiarize with the MONA-B protocol for immediate management: Morphine, Oxygen, Nitroglycerin, Aspirin, and Beta blockers.

  • Medications for Angioplasty: Prepare to administer Abciximab (ReoPro) prior to procedures as it helps prevent thombus formation.