myocardial%20infarction%20w_%20st-segment%20elevation
MYOCARDIAL INFARCTION W/ ST-SEGMENT ELEVATION
Treatment Guideline Chart
Myocardial infarction is death of cardiac myocytes (irreversible necrosis) caused by prolonged ischemia. The term "acute" usually refers to the time 6 hours to 7 days following pathologic appearance of the infarct.
The patient may experience ischemic-type chest discomfort with accompanying symptoms of nausea, vomiting, dyspnea, diaphoresis, palpitations, lightheadedness, dizziness, confusion, syncope, fatigue and weakness.
Rapid diagnosis and risk stratification of chest pain in patients are important to identify acute myocardial infarction patients who will benefit from reperfusion therapy.

Myocardial%20infarction%20w_%20st-segment%20elevation Treatment

Pre-hospital and Emergency Department Management

  • Activate Emergency Medical Services (EMS) system
  • Twelve-lead ECG
  • Administer O2: 3-4 L/min if O2 sat <90% 
  • Aspirin: 150-300 mg chew and swallow (for patients without hypersensitivity or major GI intolerance to Aspirin)
  • Nitrate: One to three doses of sublingual Glyceryl trinitrate (GTN) at 5-minute intervals or Isosorbide dinitrate (ISDN); IV if pain continues
  • Opioid (IV): 1-5 mg Morphine if pain continues 
  • Cardiac biomarkers (Troponins, CK-MB)
  • Rest if related to effort
  • Standby for resuscitation if needed
  • Recommendations and practices may vary between countries. Please refer to available guidelines from local health authorities.

Pharmacotherapy

EMERGENCY DEPARTMENT AND ACUTE CARE

Relief of Pain

  • Tranquilizer may be helpful in anxious patients
  • NSAIDs (except Aspirin) and cyclooxygenase-2 (COX-2) inhibitors should be discontinued, if regularly used prior to AMI, due to association with increased cardiovascular risk and prothrombotic effects

Opioid (IV)

  • Eg Morphine (analgesic of choice for STEMI-related pain), Diamorphine
  • Should be administered selectively for severe pain at the time of diagnosis if patient is unresponsive to nitrates and other anti-ischemic treatments
  • Pain is associated with sympathetic activation that results in vasoconstriction and an increase in the workload of the heart
  • Avoid intramuscular (IM) administration
  • Use with caution in inferior wall or posterior wall MI
  • Anti-emetics may be given concurrently with opioids to minimize nausea

Antiplatelet Therapy

  • DAPT is recommended in patients with STEMI who are undergoing primary PCI and for patients undergoing fibrinolysis and subsequent PCI  
  • In the acute phase of STEMI, a loading dose of Aspirin and Clopidogrel, Prasugrel or Ticagrelor may be given for patients undergoing primary PCI; for those receiving fibrinolytic therapy, a loading dose of Aspirin and Clopidogrel may be given

Aspirin

  • Should be given promptly and ideally within the first 24 hours of suspected MI unless there are contraindications
    • Non-enteric-coated, chewable and soluble Aspirin formulations are preferred due to their faster onset of action
  • When dose >160 mg is given, Aspirin gives rapid clinical antithrombotic action which is caused by near-total and immediate inhibition of thromboxane A2 production
  • Treatment of evolving AMI with Aspirin with or without thrombolytics has shown to reduce mortality

Reperfusion with Thrombolytic Therapy (IV)

  • IV thrombolytics should be administered to patients with minimum delay in those with confirmed MI and do not have contraindications
    • “Door to needle” time should be within 30 minutes from arrival at the hospital
    • The most benefit is seen when administered <6 hours after onset of symptoms
    • Lesser, but still important benefit is seen when given 6 to 12 hours after onset of symptoms
    • Should not be given >12 hours after symptom onset except in patients with ongoing ischemia
  • Proven to decrease morbidity and mortality when AMI is treated promptly with Aspirin and thrombolytic regimens
  • Choice of agent will depend on an individualized assessment of risk and benefit, availability and cost
    • Fibrin-nonspecific agents (eg Streptokinase and Anistreplase)
    • Fibrin-specific agents (eg Alteplase [t-PA], Reteplase [r-PA]), Tenecteplase [TNK-tPA])
      • For late-treated patients (>6 hours) or patients with hypotension, LV failure, or cardiac arrest, fibrin-specific agents are preferred
  • Monitor ST-segment elevation, cardiac rhythm, clinical symptoms 1 to 3 hours after thrombolytic therapy

Fibrinolytic Agents

  • Alteplase 
    • Fibrin specific and has better reperfusion at 90 minutes
    • Heparin should be given for 48 hours due to high rate of reocclusion
  • Streptokinase
    • Not fibrin specific and less efficacious than fibrin-selective agents
    • Antigenic and promotes antibody production
  • Tenecteplase
    • Second generation fibrin-specific agent that has a slightly lower bleeding risk
    • Given as single or double bolus injections that do not induce production of antibody
    • Heparin or Enoxaparin should be given after completing fibrinolytic therapy and continued for at least 48 hours

Ancillary Therapy

  • Patients undergoing reperfusion with thrombolytic therapy should be given anticoagulant therapy for ≥48 hours up to 8 days
    • If anticoagulant therapy should be given >48 hours, unfractionated Heparin (UFH) should be used with caution because of the small risk of Heparin-induced thrombocytopenia
    • UFH, Enoxaparin and Fondaparinux have established efficacy as ancillary anticoagulant regimens
  • Patients undergoing reperfusion with primary percutaneous coronary intervention (PCI) should be given supportive anticoagulant therapy during the procedure only
    • UFH, Enoxaparin, Bivalirudin are recommended
    • If Fondaparinux is used, anticoagulant with anti-IIa activity (eg UFH, Bivalirudin) should be added

Anticoagulants

  • Unfractionated Heparin (UFH) 
    • Important adjunctive therapy after tPA-derived agents (t-PA, r-PA, TNK-tPA, Streptokinase or Anistreplase)
      • Intravenous UFH for 48 hours and continue in patients at high risk of thromboembolism
    • If patient is at high risk of venous thromboembolism (VTE), they should receive intravenous UFH for 48 hours then consider converting to subcutaneous Heparin, Warfarin or Aspirin
      • High-risk patients: Anterior MI, existing HF, previous embolus, atrial fibrillation or left ventricular (LV) thrombus
  • Bivalirudin 
    • Useful supportive anticoagulant for primary PCI with or without prior treatment with UFH 
    • Can be considered in STEMI patients who will undergo PCI and are at high risk of bleeding or have a history of heparin-induced thrombocytopenia 
    • Not recommended as an alternative to UFH in patients who received thrombolytic therapy with Streptokinase to avoid excess major bleeding
  • Enoxaparin 
    • Can also be used to support rescue PCI
    • No additional anticoagulant needed
    • Use is indicated for patients with creatinine <2.5 mg/dL (190.6 µmol/L) in men and <2.0 mg/dL (152.5 µmol/L) in women
    • Preferred over UFH for anticoagulation extending beyond 48 hours
  • Fondaparinux 
    • When used alone to support PCI, there is increased risk for catheter thrombosis, therefore, use of additional anticoagulant with anti-IIa activity is warranted
    • Use is indicated for patients with creatinine <3.0 mg/dL (228.7 mmol/L)

Statin Therapy

  • It is recommended to initiate high-intensity statins as early as possible in all patients with STEMI (unless contraindicated) and maintain it long-term 
  • Studies show that giving a loading dose of Atorvastatin 80 mg in patients before primary PCI leads to a significant reduction in MI and major adverse cardiovascular events (MACE) 

FURTHER INPATIENT TREATMENT

Antiplatelet Therapy

Dual Antiplatelet Therapy (DAPT)

  • Eg Aspirin + Clopidogrel/Prasugrel/Ticagrelor (P2Y12 inhibitors)
  • Aspirin should be administered daily and continued indefinitely to all patients without contraindications
  • P2Y12 inhibitor therapy is given:
    • Post-fibrinolysis for 1 month to 12 months depending on the ischemic versus bleeding risks  
    • After PCI (BMS or DES) for at least 12 months; after CABG, P2Y12 inhibitor therapy is resumed to complete 12 months of DAPT  
      • In patients at high risk of complications with severe bleeding, consider stopping P2Y12 inhibitors after 6 months
  • Continuation of DAPT for >12 months may be reasonable if there is no high risk of bleeding and no significant overt bleeding on DAPT

Aspirin

  • Standard first-line antiplatelet therapy
  • Aspirin 75-100 mg/day is recommended after stenting, in patients with a prior MI or revascularization, and in those being treated with DAPT 

Clopidogrel

  • In combination with Aspirin, Clopidogrel is recommended in STEMI patients receiving thrombolysis and in whom a PCI is planned
  • Should be given in STEMI patients up to 75 years of age who are receiving fibrinolysis, Aspirin and Heparin
  • If CABG is to be performed, intake of Clopidogrel should be withheld 5 days prior to procedure

Prasugrel

  • In combination with Aspirin, Prasugrel is recommended in STEMI patients in whom coronary artery anatomy is known and PCI is planned
  • If CABG is to be performed, intake of Prasugrel should be withheld 7 days prior to procedure

Ticagrelor

  • In combination with Aspirin, Ticagrelor is recommended in STEMI patients who have undergone PCI or medical management  
  • Alternative to Clopidogrel in <75-year-old patients undergoing PCI within 24 hours after fibrinolytic therapy
  • Should be withheld 3 to 5 days prior to CABG

Cangrelor 

  • A potent, direct, reversible and short-acting intravenous P2Y12 inhibitor 
  • May be used in P2Y12 inhibitor-naive patients undergoing PCI or patients who cannot take oral medications or whose absorption of oral medications is inhibited

Glycoprotein IIb/IIIa Inhibitors

  • Adjunctive use of Abciximab, Eptifibatide or Tirofiban at the time of primary PCI can benefit patients with large thrombus burden
  • Eptifibatide or Tirofiban should be discontinued at least 2-4 hours and Abciximab at least 12 hours before urgent CABG

Anticoagulants (IV)

  • Eg UFH, Enoxaparin, Fondaparinux
  • Given to those who received fibrinolytic therapy but did not undergo PCI
  • Beneficial in MI with ST elevation
    • May also be given to patients treated with fibrin-selective lytic agents, as routine administration after fibrinolysis, and patients with atrial fibrillation or mural thrombus 
  • When Fondaparinux is used alone to support PCI, there is increased risk for catheter thrombosis; therefore, use of additional anticoagulant with anti-IIa activity (eg UFH or Bivalirudin) is warranted

ACE Inhibitors

  • Start in all patients once the blood pressure is stable and systolic blood pressure remains >100 mmHg unless contraindicated (ideally within the first 24 hours and after thrombolytic therapy)
    • Greatest benefit has been seen in patients with HF, anterior infarction, LV systolic dysfunction, diabetes
  • Associated with small but significant decrease in 30-day mortality with most of the benefit seen in the first week after infarction

Angiotensin II Antagonists

  • Use in patients who have indications for (eg early-phase HF or LVEF ≤40%) but are intolerant to ACE inhibitors

Beta-Blockers

  • Eg Atenolol, Bisoprolol, Carvedilol, Labetalol, Metoprolol, Propranolol 
  • Oral beta-blockers should be given within 24 hours of onset of infarction in low-risk patients without contraindications (eg hypotension or evidence of low output state, congestive heart failure [CHF], increased risk for cardiogenic shock, PR interval >0.24 seconds, 2nd- or 3rd-degree heart block, active asthma or reactive airway disease)
  • When given during first few hours of infarct, beta-blockers may lessen myocardial O2 demand by decreasing heart rate, systemic arterial pressure and myocardial contractility

Aldosterone Antagonists (Mineralocorticoid Receptor Antagonists)

  • Eg Eplerenone, Spironolactone
  • When added to beta-blocker and ACE inhibitor, aldosterone antagonist has been shown to reduce mortality and hospitalization rates in post-MI patients with impaired left ventricular function and mild HF

Nitrates

  • Nitrate-induced relaxation of the vascular smooth muscle in veins, arteries and arterioles results in vasodilation
    • This reduces right ventricular and left ventricular preload along with afterload reduction which decreases cardiac work and myocardial oxygen demand 
  • May be considered in the first 24 to 48 hours if needed in patients with continuing chest pain/ischemia, HF, large anterior infarction or hypertension
    • Intravenous route is usually preferred in early management (first 48 hours) because of more precise control
  • May be used beyond 48 hours if patient has recurrent angina or continued pulmonary congestion

Calcium Antagonists

  • Eg Diltiazem or Verapamil
  • Should only be considered if beta-blockers and nitrates are ineffective in controlling ischemia or if beta-blockers are contraindicated
  • May be used to control rapid ventricular response with atrial fibrillation after AMI
  • Have not been shown to reduce mortality after AMI 
  • Should not be used in patients with CHF, LV dysfunction or atrioventricular (AV) block

Statins

  • High-intensity statins should be given as concomitant pharmacotherapy in the acute treatment of all STEMI patients if without contraindications 

Glucose Control

  • Hyperglycemia is managed during the acute phase but hypoglycemic episodes should be avoided
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