Treatment - STEMI Medical Therapy

Initial medical therapy during STEMI consists of oxygen administration, antiplatelet therapy (aspirin, thienopyridines and glycoprotein IIb/IIIa inhibitors), anticoagulation, anginal pain relief with nitrates and morphine, and beta-blockade.

Medical therapy upon hospital discharge may include ACE inhibitors, angiotensin receptor blockers, aldosterone antagonists and HMG CoA reductase inhibitors.

Aspirin: Aspirin should be chewed at a dose of 162 to 325 mg immediately once STEMI is diagnosed unless a contraindication exists. Lifelong therapy using 75-162 mg daily should follow upon hospital discharge.

Thienopyridines: P2Y212 receptor antagonists (clopidogrel, prasugrel, ticagrelor, and ticlopidine) are indicated in all STEMI cases unless surgery is needed. Clopidogrel can also be used as an adjunct to fibrinolytic therapy in patients intolerant to aspirin. If coronary artery bypass grafting is required, these agents should not be used. These agents must be discontinued for 5-7 days prior to CABG unless urgent and the bleeding risk is less than the benefit of revascularization. Regardless of the type of stent used during PCI, thienopyridines are preferred to be continued for 12 months if possible. Prasugrel is not recommended in a patient with a prior history of stroke or TIA. Ticlopidine is rarely used due to the risk of thrombocytopenia and TTP (thrombotic thrombocytopenic purpura).

Glycoprotein IIb/IIIa inhibitors:  These drugs include abciximab, eptifibatide, and tirofiban. They very strongly inhibit platelet function by blocking the binding of fibrinogen to the activated glycoprotein IIb/IIIa receptor complex. Any of these agents may be used in addition to aspirin, a thienopyridine and anticoagulation (except with bivalirudin) at the time of PCI in high risk patients with STEMI. Using glycoprotein IIb/IIIa inhibitors prior to PCI does not have strong data to support its use at the present time.

Anticoagulation: Full anticoagulation should be started in all STEMI patients unless a contraindication exists. Either unfractionated heparin, low molecular weight heparin (enoxaparin or fondaparinux) or bivalirudin can be used. Unfractionated heparin for 48 hours total and low molecular weight heparin for 8 days or until hospital discharge.

Nitrates: Nitrates are helpful to treat angina symptoms, hypertension and heart failure during STEMI, however no clinical data exists to show a mortality benefit and thus their use is individualized. The use of nitrates should not preclude using drugs that do show a mortality benefit.

Sublingual nitroglycerine tablets administered every 3-5 minutes with a maximum dose of three tablets can be given to relieve angina. Should angina persist, then intravenous nitroglycerine can be considered. Hypotension or right ventricular involvement is a contraindication to their use. Phosphodiesterase inhibitors (sildenafil, vardenafil, tadalafil) used to treat erectile dysfunction enhance nitric oxide production and can cause potentially fatal hypotension when used in combination of nitrates. These two drugs should not be used together within 24 hours (sildenafil) or 48 hours (vardenafil, tadalafil) due to this interaction.

Morphine: Morphine is effective to relieve anginal chest pains and the sensation of dyspnea when pulmonary edema is present. There are also some beneficial hemodynamic effects including arterial vasodilation.

Beta-blockers: While there is little data in regards to the efficacy of beta-blockers during UA/NSTEMI, there is an abundance during STEMI. Guidelines from the American Heart Association recommend early intravenous beta-blockers when no contraindication exists and there is angina, hypertension or tachycardia not related to heart failure. Otherwise, oral beta-blocker therapy is given in the acute setting. It is important NOT to give beta-blockers if there are signs of cardiogenic shock such as hypotension or pulmonary edema on chest x-ray. Long-term therapy (lifetime) has been shown to reduce MI incidence and improve mortality. Also, if left ventricular systolic dysfunction remains after a STEMI, beta-blockers are important for chronic systolic heart failure.

ACE inhibitors/Angiotensin receptor blockers: Either an ACE inhibitor or angiotensin receptor blocker should be given to all STEMI patients upon hospital discharge. Caution must be used in the acute setting in order to avoid hypotension which can worsen myocardial ischemia. Guidelines give the use of these drugs a class I indication when there is left ventricular systolic dysfunction or if the patient is diabetic. When left ventricular function returns to normal and the patient is not diabetic, the benefits are less clear. Usually ARBs are only given if ACE inhibitors are not tolerate due to cough or other side-effects.

Aldosterone antagonists: The aldosterone antagonist eplerenone was evaluated in the EPHESUS trial leading to the recommendation for their with an ACE inhibitor prior to hospital discharge after UA/NSTEMI if there is left ventricular systolic dysfunction (EF < 40%) and either diabetes or symptomatic heart failure present and no contraindication (serum creatinine > 2.5 and or potassium > 5.0). A class effect is likely present and thus spironolactone is frequently used instead of eplerenone due to cost concerns, although there is no direct data to support this practice.

HMG-CoA reductase inhibitors: Every patient with STEMI should receive therapy with a statin. The 2013 ACC/AHA cholesterol guidelines recommend high intensity statin therapy (defined as LDL reduction > 50%) in those age < 75 and moderate intensity (defined as 30-50% reduction of LDL) in those > 75 years old. No specific target LDL are recommend in these guidelines, simply a reduction of LDL levels from baseline. The MIRACLE and PROVE-IT TIMI 22 trial used atorvastatin 80 mg PO daily with good results. Statin therapy should be lifetime after a person has an acute coronary syndrome unless a contraindication exists.

Calcium Channel Blockers: The non-dihydropyridine calcium channel blockers diltiazem and verapamil can be used when there is a contraindication to beta-blockers (such as asthma) and there is no heart failure or significant left ventricular systolic dysfunction present. Sublingual nifedipine is contraindicated due to a reflexive increase in the sympathetic nervous system which can be harmful.

PROCEED TO STEMI - SPECIAL SITUATIONS

Related links:

Introduction

Pathophysiology

Physical Examination

Diagnosis

Treatment - Revascularization

Treatment - Medical

Special Situations

Review Questions - STEMI - Multiple Choice

Review Questions - STEMI - Case Based

Acute Coronary Syndromes Jeopardy