What is the diagnosis and treatment for ST-Elevation Myocardial Infarction (STEMI)?

From the Guidelines

STEMI (ST-Elevation Myocardial Infarction) requires immediate medical attention with aspirin 325mg chewed immediately, followed by dual antiplatelet therapy and primary percutaneous coronary intervention (PCI) within 90 minutes of first medical contact, as it represents a complete blockage of a coronary artery. The treatment of STEMI should prioritize reducing morbidity, mortality, and improving quality of life. According to the most recent and highest quality study 1, aspirin inhibits the formation of thromboxane A2, a potent stimulator of platelet aggregation, and is the first-line therapy for AMI.

Key Components of STEMI Treatment

• Aspirin 325mg chewed immediately, followed by an 81-mg daily dose to minimize bleeding risk 1
• Dual antiplatelet therapy including clopidogrel 600mg, ticagrelor 180mg, or prasugrel 60mg loading dose
• Primary percutaneous coronary intervention (PCI) within 90 minutes of first medical contact, as it is the preferred reperfusion strategy 1
• If PCI is not available within this timeframe, fibrinolytic therapy (such as alteplase, reteplase, or tenecteplase) should be administered within 30 minutes of arrival
• Additional medications include anticoagulation with unfractionated heparin or low molecular weight heparin, beta-blockers (such as metoprolol 5mg IV followed by oral therapy), and high-intensity statins (atorvastatin 80mg or rosuvastatin 40mg daily) 1
• Oxygen should be administered only if saturation is below 90%

Secondary Prevention

Following acute management, patients require secondary prevention with dual antiplatelet therapy for 12 months, statins, ACE inhibitors or ARBs, and beta-blockers. This approach has been shown to reduce mortality and subsequent cardiovascular events in STEMI patients 1.

Importance of Timely Treatment

STEMI requires urgent treatment because prolonged coronary occlusion leads to irreversible myocardial necrosis, with the amount of heart muscle damage directly correlating with time to reperfusion. Therefore, it is crucial to prioritize timely treatment to minimize morbidity, mortality, and improve quality of life.

From the FDA Drug Label

5.5 Increased Risk of Heart Failure and Recurrent Ischemia when used with Planned Percutaneous Coronary Intervention (PCI) in STEMI. In a trial of patients with STEMI, there were trends toward worse outcomes in the individual components of the primary endpoint between TNKase plus PCI versus PCI alone (mortality 6.7% vs. 4.9%, respectively; cardiogenic shock 6.3% vs. 4.8%, respectively; and CHF 12% vs. 9.2%, respectively). In addition, there were trends towards worse outcomes in recurrent MI (6.1% vs. 3.7%, respectively; p = 0.03) and repeat target vessel revascularization (6.6% vs. 3.4%, respectively; p = 0.0045) in patients receiving TNKase plus PCI versus PCI alone [see Clinical Studies (14.1)]. In patients with large ST segment elevation myocardial infarction, physicians should choose either thrombolysis or PCI as the primary treatment strategy for reperfusion Rescue PCI or subsequent elective PCI may be performed after administration of thrombolytic therapies if medically appropriate; however, the optimal use of adjunctive antithrombotic and antiplatelet therapies in this setting is unknown.

The use of tenecteplase in patients with STEMI may increase the risk of heart failure and recurrent ischemia when used with planned PCI.

• Mortality rates were higher in patients receiving TNKase plus PCI compared to PCI alone (6.7% vs 4.9%).
• Cardiogenic shock and CHF rates were also higher in patients receiving TNKase plus PCI (6.3% vs 4.8% and 12% vs 9.2%, respectively).
• Recurrent MI and repeat target vessel revascularization rates were higher in patients receiving TNKase plus PCI (6.1% vs 3.7% and 6.6% vs 3.4%, respectively) 2. It is recommended that physicians choose either thrombolysis or PCI as the primary treatment strategy for reperfusion in patients with large ST segment elevation myocardial infarction.

From the Research

STEMI Management

• The management of STEMI patients is crucial in determining the outcome, with the goal of keeping time intervals between symptom onset and reperfusion therapy as short as possible 3.
• The first-line management of STEMI patients often determines if the outcome is life or death, with primary PCI being the preferred treatment if it can be performed within 120 minutes of first medical contact (FMC) 3, 4.
• If primary PCI is not possible within 120 minutes, thrombolysis should be initiated within 30 minutes after FMC, either in the EMS ambulance or in a nearby non-PCI hospital 3.

Antiplatelet Therapy

• Dual antiplatelet therapy (DAPT) with aspirin and a thienopyridine is mandatory for STEMI patients, with prasugrel being preferred over clopidogrel due to its faster onset of action and superior effectiveness 3, 5.
• Prasugrel has been shown to significantly reduce nonfatal myocardial infarction and stent thrombosis compared to clopidogrel 3.
• The use of oral P2Y12 inhibitors, such as prasugrel and ticagrelor, is recommended for STEMI patients undergoing primary PCI, with a loading dose of 60 mg for prasugrel and a maintenance dose of 10 mg/day 4, 5.

Pre-Hospital Treatment

• Pre-hospital antiplatelet therapy has been shown to be effective in reducing the duration of ischemia and improving outcomes in STEMI patients 6.
• New parenteral drugs that achieve immediate inhibition of platelet aggregation may create the opportunity to bridge the initial gap in platelet inhibition observed with oral P2Y12 inhibitors 6.
• The potential anti-ischaemic benefits of potent antiplatelet agents will need to be balanced against their risk of increased bleeding 6.

Reperfusion Therapy

• Primary PCI has become the preferred reperfusion strategy in patients with STEMI, with a goal of performing the procedure within 120 minutes of STEMI diagnosis 7.
• If PCI cannot be performed within 120 minutes, fibrinolysis therapy should be administered to dissolve the occluding thrombus 7.
• The initiation of networks to provide around-the-clock cardiac catheterization availability and the generation of standard operating procedures within hospital systems have helped to reduce the time to reperfusion therapy 7.