ST-elevation myocardial infarction

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

The main goals of treatment are to limit myocardial damage by restoring myocardial blood flow as quickly as possible and to decrease subsequent remodeling, which can have deleterious effects on ventricular function and prognosis.[69][87]

Immediate and prompt revascularization with percutaneous coronary intervention (PCI) within 90 minutes of first presentation, or thrombolysis within 12 hours of symptom onset, can prevent or decrease myocardial damage and decrease morbidity and mortality by preventing acute complications.[69][106][107] It is strongly recommended that local communities or regional areas should develop a rapid response system for treatment of STEMI. The optimal coronary revascularization strategy may not be clear for all patients with STEMI (e.g., if there is complex coronary disease and/or comorbid conditions); this is more likely to apply to older patients.[108]

American College of Cardiology/American Heart Association guidelines recommend a patient-centered shared decision-making process for such patients, utilizing a multidisciplinary team that includes representatives from interventional cardiology, cardiac surgery, and clinical cardiology.[67][106][108]

Initial management

The patient should be admitted to a unit with continuous cardiac monitoring and started on strict bed rest for the first 12-24 hours. Supplemental oxygen may be administered if oxygen saturation is less than 90%.[3][69] Liberal use of oxygen is associated with increased mortality in patients with acute coronary syndrome.[109][110] Guidelines recommend that oxygen should not be routinely administered in normoxic patients with suspected or confirmed acute coronary syndrome (ACS).[3][69][74]

Aspirin is given immediately.

Adequate analgesia with morphine is essential to relieve pain and its related sympathetic activity, which can further increase myocardial oxygen demand.

Nitroglycerin should also be given immediately, if the patient is not hypotensive, as it reduces myocardial oxygen demand and lessens ischemia, and may rarely abort MI if there is coronary spasm. However, it should not be given in doses that interfere with analgesic therapy. Sublingual dosing should be given first to all patients, while intravenous therapy is reserved for patients with hypertension or heart failure.

Hemodynamically unstable

Cardiogenic shock occurs in 5% to 10% of people presenting with STEMI, and the in-hospital mortality is ≥50%.[89][90]

If revascularization with PCI fails or is not feasible, urgent coronary artery bypass graft (CABG) is recommended for patients with cardiogenic shock or hemodynamic instability.[89][90][106]

Patients with low cardiac output states and cardiogenic shock may benefit from a dobutamine infusion.[89][90] Guidelines state that adjunctive use of an intra-aortic balloon pump (IABP) or a ventricular mechanical circulatory support device may be reasonable in selected patients at risk of hemodynamic compromise during PCI (e.g., in patients with severe peripheral artery or aortic disease).[89][90][106] Results from observational studies appear to be conflicting for IABP in acute MI, and in randomized controlled trials (RCTs) it has not been shown to reduce mortality after acute MI even in patients with cardiogenic shock.[111] [ ]

Antiplatelet and anticoagulant therapy

Antiplatelet and anticoagulant agents are indicated for the treatment of STEMI as they limit secondary thrombosis by inhibiting platelet activation and subsequent platelet aggregation.

Aspirin should be given to all patients, along with ticagrelor or prasugrel.[3][112] Prasugrel and ticagrelor are associated with reduced ischemic events compared to clopidogrel, though there is also an increased bleeding risk with these agents.[113][114][115] Prasugrel is contraindicated in patients with a history of ischemic stroke or transient ischemic attack, and its use is not recommended in patients >75 years of age or in patients with low body weight (<60 kg) due to increased bleeding risk (though dose reductions may mitigate this risk); therefore, ticagrelor is often more widely used.[69][106][116][117] Ticagrelor may be associated with higher risk of bleeding and death than clopidogrel in older patients.[118] Clopidogrel is an alternative P2Y12 inhibitor that may be used when ticagrelor and prasugrel are contraindicated or unavailable.[3][118] Cangrelor, an intravenous P2Y12 inhibitor, can be used as an adjunct to PCI to reduce the risk of periprocedural MI, repeat coronary revascularization, and stent thrombosis in patients who have not previously been treated with a P2Y12 inhibitor and are not being treated with a glycoprotein IIb/IIIa inhibitor.[3][119]
Unfractionated heparin is the preferred anticoagulant to be used as a single agent in addition to antiplatelet therapy. Alternatively, bivalirudin and enoxaparin can be used.[3] Additional glycoprotein IIb/IIIa inhibitors (GPIIb/IIIa inhibitors) are only recommended if there is evidence of slow flow, no-reflow, or a thrombotic complication at PCI.[3][106]

Supportive measures

Adequate analgesia with morphine is essential to relieve pain and its related sympathetic activity, which can further increase myocardial oxygen demand.
Supplemental oxygen may be administered if oxygen saturation is less than 90%.[3][69] Guidelines recommend that oxygen should not be routinely administered in normoxic patients with suspected or confirmed ACS.[3][69][74]
Glycemic control, including the use of insulin where appropriate, should also be maintained, although rigid control has not been shown to be beneficial in critically ill patients.[22]

Electrically unstable: post-cardiac arrest

Emergency revascularization is recommended in patients with a cardiac arrest who have been resuscitated and are hemodynamically stable and show ECG evidence for a STEMI. Staged PCI of a significant non-infarct artery stenosis is recommended after successful primary PCI in selected hemodynamically stable patients with multivessel disease.[106] Alternatively, multivessel PCI may be considered at the time of primary PCI in selected patients, although the evidence supporting this strategy is weaker.[106] However, physicians should consider clinical data, lesion severity/complexity, and risk of contrast nephropathy to determine the optimal PCI strategy (primary or staged).

Emergency CABG is contraindicated in post-cardiac arrest patients who are comatose.

Thrombolysis is a potential option if PCI is not readily available, but prolonged CPR is a contraindication to the use of thrombolytics.

Hypothermia is recommended for cardiac arrest patients who have been resuscitated and remain comatose.

Hemodynamically stable: PCI available within 90 minutes of first medical contact

PCI

Primary PCI, with stent placement (using bare metal stents or drug-eluting stents), is the preferred method of revascularization, provided it can be performed in a timely manner with an experienced team of operators. Primary PCI is recommended for patients presenting within 12 hours of symptom onset and can be beneficial for patients presenting between 12 and 24 hours of symptom onset, though is most effective when symptom-to-balloon times are minimized.[87][106][107][120][121] It involves immediate transfer to the catheterization laboratory with the intention of opening the artery with stent placement. Drug-eluting stents are preferred.[3][122][123] [ ] Third-generation drug-eluting stents composed of biodegradable polymers are currently being investigated.[124][125][Figure caption and citation for the preceding image starts]: Angiogram showing occluded right coronary arteryFrom the personal collection of Dr Mahi Ashwath; used with permission [Citation ends].[Figure caption and citation for the preceding image starts]: Angiogram showing an attempt to open the occluded right coronary artery with an angioplasty balloonFrom the personal collection of Dr Mahi Ashwath; used with permission [Citation ends].[Figure caption and citation for the preceding image starts]: Angiogram after balloon angioplasty and stenting showing an open right coronary arteryFrom the personal collection of Dr Mahi Ashwath; used with permission [Citation ends].
Radial approach is preferable to femoral approach as it results in better outcomes (e.g., reduction in mortality, major adverse cardiovascular events, major bleeding, and bleeding complications), particularly if the operator is experienced in radial access.[87][106][126][127][128]
Staged PCI of a significant non-infarct artery stenosis is recommended after successful primary PCI in selected hemodynamically stable patients with STEMI and multivessel disease.[106] Alternatively, multivessel PCI may be considered at the time of primary PCI in selected patients, although the evidence supporting this strategy is weaker.[106][129][130][131] Physicians should consider factors such as clinical data, hemodynamic stability, lesion severity/complexity, and risk of contrast nephropathy to determine the optimal PCI strategy. Calculation of the SYNTAX score is recommended for left main or multivessel PCI. SYNTAX score Opens in new window
Guidelines also recommend against routine manual aspiration thrombectomy before primary PCI as the evidence does not suggest any benefit of this procedure over PCI alone.[106][132] Furthermore, studies have suggested that routine aspiration thrombectomy might increase the risk of stroke.[133][134]

Many hospitals have 24-hour PCI capacity; however, in facilities without catheterization laboratories, routine transfer to a PCI facility should be considered for all patients if transfer times are reasonable and total ischemic time after presentation is less than 120 minutes.[106]

Early revascularization prevents scar formation, decreases the occurrence of heart failure later on, and decreases the incidence of future ventricular arrhythmias caused by scar formation.

CABG

Emergency revascularization with CABG can be useful if PCI fails or is not feasible, and a large area of myocardium is at risk.[106]
CABG is recommended for patients with cardiogenic shock or heart failure if PCI is not feasible.[89][90][106]
CABG should not be undertaken after failed primary PCI in the absence of ischemia or a large area of myocardium at risk, or if surgical revascularization is not feasible due to a no-reflow state or poor distal targets.[106]

Antiplatelet and anticoagulant therapy

Antiplatelet and anticoagulant agents are indicated for the treatment of STEMI as they limit secondary thrombosis by inhibiting platelet activation and subsequent platelet aggregation.

Aspirin should be given to all patients, along with ticagrelor or prasugrel.[3][112] Prasugrel and ticagrelor are associated with reduced ischemic events compared to clopidogrel, though there is also an increased bleeding risk with these agents.[113][114][115] Prasugrel is contraindicated in patients with a history of ischemic stroke or transient ischemic attack, and its use is not recommended in patients >75 years of age or in patients with low body weight (<60 kg) due to increased bleeding risk (though dose reductions may mitigate this risk); therefore, ticagrelor is often more widely used.[69][106][116][117] Ticagrelor may be associated with higher risk of bleeding and death than clopidogrel in older patients.[118] Clopidogrel is an alternative P2Y12 inhibitor that may be used when ticagrelor and prasugrel are contraindicated or unavailable.[3][118] Cangrelor, an intravenous P2Y12 inhibitor, can be used as an adjunct to PCI to reduce the risk of periprocedural MI, repeat coronary revascularization, and stent thrombosis in patients who have not previously been treated with a P2Y12 inhibitor and are not being treated with a GPIIb/IIIa inhibitor.[3][119]

Unfractionated heparin is the preferred anticoagulant to be used as a single agent in addition to antiplatelet therapy. Alternatively, bivalirudin and enoxaparin can be used. Additional glycoprotein IIb/IIIa inhibitors (GPIIb/IIIa inhibitors) are only recommended if there is evidence of slow flow, no-flow, or a thrombotic complication at PCI.[106]

Supportive measures

Oral beta-blockers should be started as soon as possible, as they decrease infarction size and reduce mortality, although care should be taken in patients with evidence of heart failure, hypotension, bradycardia, or asthma.[69][135][136] Intravenous beta-blockers are recommended only in patients who are hypertensive or have ongoing ischemia, provided there are no contraindications to their use.[69][137]

In the absence of contraindications, high-intensity statin therapy (i.e., statin regimens that reduce LDL-cholesterol by ≥50%) should be initiated or continued in all stabilized patients with STEMI.[69][138]
Eplerenone should be added to optimal medical therapy in eligible patients (creatinine <2.5 mg/dL in men and <2.0 mg/dL in women; potassium <5.0 mEq/L) 3-14 days after STEMI with ejection fraction <0.40, and either symptomatic heart failure or diabetes mellitus.[69][139] Earlier initiation of the drug (<7 days) has been shown to significantly reduce the rates of all-cause mortality, sudden cardiac death, and cardiovascular mortality/hospitalization, whereas initiation >7 days has not been shown to have a significant effect on outcomes.[140]

Adequate analgesia with morphine is essential to relieve pain and its related sympathetic activity, which can further increase myocardial oxygen demand. Nitroglycerin should also be given immediately if the patient is not hypotensive.

Supplemental oxygen may be administered if oxygen saturation is less than 90%.[3][69] Guidelines recommend that oxygen should not be routinely administered in normoxic patients with suspected or confirmed ACS.[3][69][74]

Glycemic control, including the use of insulin where appropriate, should also be maintained, although rigid control has not been shown to be beneficial in critically ill patients.[22]

Nonsteroidal anti-inflammatory drugs should be avoided, and stopped if possible in patients already on them.[141]

Hemodynamically stable: PCI available >90 minutes after first medical contact and within 12 hours of symptom onset with no contraindications to thrombolysis

Thrombolysis is indicated if PCI is not available within 90 minutes of first medical contact and the patient has no contraindications to thrombolytic therapy.[142][143] It should be initiated within 30 minutes of presentation. Thrombolysis is used only once on initial diagnosis, and this must be within 12 hours of symptom onset (ideally within 3 hours) as the efficacy of fibrinolytic agents in lysing the thrombus diminishes over time. Therapy within the first 2 hours (particularly the first hour) can occasionally abort MI and dramatically reduce mortality.[69]

Absolute contraindications for thrombolysis are any prior intracranial hemorrhage, known malignant intracranial lesion or structural cerebral vascular lesion (e.g., arteriovenous malformations), ischemic stroke within previous 3 months, suspected aortic dissection, active bleeding or bleeding diathesis, and significant closed head or facial trauma within previous 3 months.[69]

Thrombolytics can be associated with an increased risk of bleeding, in addition to the risk associated with other antithrombotic and/or antiplatelet agents used, and can also cause intracranial hemorrhage.

Transfer to a PCI-capable hospital within 24 hours should be considered in all patients undergoing fibrinolytic therapy. Angiography with intent to fully revascularize the culprit vessel should be considered within 24 hours even after successful fibrinolytic therapy (i.e., treatment of residual stenosis or suboptimal flow of the infarct artery).[87][106][143]

Rescue PCI after thrombolysis is recommended in patients with evidence of failed reperfusion (such as ongoing chest pain; hemodynamic, mechanical, or electrical instability; or shock). Treated patients should be transferred for PCI as soon as possible after thrombolysis.[3][144] Those transferred within 6 hours after thrombolytic therapy had significantly fewer ischemic complications than those who were only transferred if they had complications.[145] Rescue PCI is associated with improved clinical outcomes after failed fibrinolytic therapy.[146]

Antiplatelet and anticoagulant agents (e.g., oral aspirin and clopidogrel; intravenous heparin) are also indicated for the treatment of STEMI, as this limits secondary thrombosis by inhibiting platelet activation and subsequent platelet aggregation. Prasugrel and ticagrelor are not recommended in patients undergoing thrombolysis as they have not been adequately studied in this setting.[147] GPIIb/IIIa inhibitors are not indicated in STEMI if thrombolytic therapy is indicated. Low molecular weight heparin should be considered instead of unfractionated heparin in patients treated with thrombolysis.[3][148][149]

Supportive measures are the same as those for patients who undergo PCI within 90 minutes.

Hemodynamically stable: PCI available >90 minutes after first medical contact and within 12 hours of symptom onset with contraindications to thrombolysis

In patients with contraindications to thrombolysis, PCI is indicated even if it cannot occur within 90 minutes. Patients should be transferred for PCI as soon as possible.

Antiplatelet/anticoagulant agents and supportive measures are the same as those for patients who undergo PCI within 90 minutes.

Hemodynamically stable: no access to PCI within 90 minutes and >12 hours after symptom onset

Even beyond 12 hours, if there are persistent symptoms, it is possible to obtain benefits from revascularization, which would be best performed with percutaneous coronary revascularization. Stable patients in whom PCI or thrombolysis is not indicated are treated with pharmacotherapy only, including beta-blockers and antiplatelet and anticoagulation therapy. If the patient becomes unstable, they should undergo late PCI, which can be done up to 36 hours after the onset of symptoms.[106][150]

Routine primary PCI strategy should still be considered in patients presenting between 12 and 48 hours after symptom onset. However, if the time since symptom onset is >48 hours and the patient is now asymptomatic, routine PCI of an occluded infarct-related artery is not recommended.[3][151]

Supportive measures are the same as those for patients who undergo PCI within 90 minutes.

Post-STEMI

The American College of Cardiology/American Heart Association guidelines recommend that, where available, cardiac rehabilitation/secondary prevention programs are provided for patients with STEMI, particularly those with multiple modifiable risk factors and/or those moderate- to high-risk patients in whom supervised exercise training is warranted.[152][153][154] [ ] [Evidence A] Systematic review evidence has shown exercise‐based cardiac rehabilitation helps to improve outcomes in people with coronary heart disease.[155]

Patients without any preexisting risk factors for cardiovascular disease (CVD) are at increased risk of early mortality; even patients who are deemed low risk require prompt initiation of evidence-based pharmacotherapy post ACS.[156]

Dual antiplatelet therapy should usually be continued in all patients for at least 12 months, whether they were stented or not.[69][157] In selected patients undergoing PCI, shorter-duration dual antiplatelet therapy (1-3 months) can be considered, with subsequent transition to P2Y12 inhibitor monotherapy to reduce the risk of bleeding events.[106][158][159][160][161][162]

Statin therapy should be given indefinitely if tolerated and not contraindicated.[69][138] For patients at very high risk of future events, and those up to 75 years of age and not at very high risk, ezetimibe may be added if the patient is on maximal statin therapy, and LDL-cholesterol level remains ≥70 mg/dL.[163] A proprotein convertase subtilisin/kexin type 9 (PCSK9) antibody inhibitor (evolocumab or alirocumab) may be added to maximal statin and ezetimibe therapy if the patient is at very high risk of future events and LDL-cholesterol level remains ≥70 mg/dL, or non-HDL-cholesterol ≥100 mg/dL.[3][43][163][164] Patients are considered to be at very high risk of future events if they have a history of multiple major atherosclerotic CVD events (recent ACS [within the past 12 months], MI other than the recent ACS, ischemic stroke, symptomatic peripheral arterial disease [claudication with ankle brachial index <0.85, previous revascularization or amputation]), or one major atherosclerotic CVD event and multiple high risk conditions (age ≥65 years, heterozygous family history, history of previous CABG or PCI, diabetes mellitus, hypertension, chronic kidney disease, current smoking, persistently elevated LDL-cholesterol [≥100 mg/dL {≥2.6 mmol/L}] despite maximally tolerated therapy, history of congestive heart failure).[163]

ACE inhibitors should be started early (i.e., when patient is hemodynamically stable, optimally on first day in the hospital) for a favorable effect on ventricular remodeling, especially in patients with large anterior wall MI. Beta-blockers should be continued long term (>1 year) - continuing use should then be evaluated on the basis of comorbidities.[135][165][166][167] The American College of Cardiology/American Heart Association recommend that the decision to continue beta-blockers long term after revascularization should be made on an individualized basis.[106]

A sodium-glucose cotransporter-2 (SGLT2) inhibitor, such as dapagliflozin or empagliflozin, should be given to patients with heart failure when they are clinically stable, regardless of their left ventricular ejection fraction.[168][169][170]

Chronic nitrate use is not routinely recommended after a MI, but may be used as part of the treatment plan for congestive heart failure and for chronic angina.

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