Myocardial Infarction

Acute MI requires evidence of acute myocardial injury—cardiac troponin rise and/or fall with at least one value above the 99th-percentile upper reference limit—plus clinical evidence of acute myocardial ischemia. The ischemic evidence may be symptoms, new ischemic ECG changes, pathologic Q waves, new loss of viable myocardium or regional wall-motion abnormality, or coronary thrombus. Troponin elevation without ischemic evidence should be classified as myocardial injury rather than MI.BMJ+1BMJNon-ST-elevation myocardial infarctionNatureMachine learning for diagnosis of myocardial infarction using cardiac troponin concentrations | Nature Medicine

Type 1 MI reflects acute coronary atherothrombosis. Type 2 MI reflects ischemic supply-demand imbalance without acute atherothrombosis, such as tachyarrhythmia, hypotension, or anemia. Classification should change management: type 2 MI requires correction of the precipitating process and careful evaluation for underlying coronary disease rather than reflex application of a type 1 MI antithrombotic pathway.NatureNatureMachine learning for diagnosis of myocardial infarction using cardiac troponin concentrations | Nature Medicine

Obtain a 12-lead ECG immediately in patients with suspected acute coronary syndrome. For STEMI, ST-segment elevation should be present in at least two contiguous leads: at least 1 mm in leads other than V2-V3; in V2-V3, thresholds are at least 2.5 mm in men younger than 40 years, 2 mm in men 40 years or older, and 1.5 mm in women.BMJBMJST-elevation myocardial infarction - Symptoms, diagnosis and treatment | BMJ Best Practice US

A nondiagnostic ECG does not exclude MI. NSTEMI may present with ST depression, T-wave inversion, transient ST elevation, or a normal/nonspecific tracing. Repeat ECGs are appropriate when symptoms persist or evolve. Posterior MI or persistent ST elevation should be managed as STEMI.BMJ+1BMJNon-ST-elevation myocardial infarctionPubMedAcute ST-Segment Elevation Myocardial Infarction (STEMI)

Primary PCI is the preferred reperfusion approach for most patients with STEMI. Patients with ischemic symptoms of less than 12 hours' duration should undergo primary PCI when it can be performed within 120 minutes; patients with cardiogenic shock or acute severe heart failure warrant PCI regardless of time from symptom onset.PubMedPubMedAcute ST-Segment Elevation Myocardial Infarction (STEMI)

When primary PCI cannot be delivered within 120 minutes and there is no contraindication, fibrinolysis is an alternative reperfusion strategy. Patients receiving fibrinolysis should be transferred to a PCI-capable center. Failed lysis, reocclusion, or reinfarction requires immediate angiography and rescue PCI; even apparent successful reperfusion should be followed by angiography within 2 to 24 hours.PubMedPubMedAcute ST-Segment Elevation Myocardial Infarction (STEMI)

NSTEMI is distinguished from unstable angina by a troponin rise above the 99th percentile in an ischemic clinical context. Because presentations range from stable injury to shock, early risk assessment directs diagnostic and therapeutic choices, including the timing of invasive coronary angiography.BMJBMJNon-ST-elevation myocardial infarction

Urgent invasive evaluation is appropriate for refractory ischemia or hemodynamic or electrical instability. Stable patients require serial troponin and ECG assessment plus structured risk stratification to determine whether and when angiography should occur.BMJ+1BMJNon-ST-elevation myocardial infarctionPubMed2025 ACC/AHA/ACEP/NAEMSP/SCAI Guideline for the ...

Before discharge, assess left ventricular function and identify residual ischemia, heart failure, arrhythmia, and mechanical complications. Persistent or recurrent angina, dyspnea, hypotension, new murmur, pulmonary edema, or shock after MI should trigger prompt evaluation for ischemic, electrical, or mechanical complications.BMJ+1BMJST-elevation myocardial infarction - Symptoms, diagnosis and treatment | BMJ Best Practice USPubMedReview of Current Management of Myocardial Infarction

High-intensity statin therapy should be initiated promptly after MI irrespective of baseline lipid level. Aspirin and a P2Y12 inhibitor are foundational after ACS, but the duration and intensity of antiplatelet treatment must be individualized against bleeding risk and the revascularization strategy.PubMed+1PubMedReview of Current Management of Myocardial InfarctionPubMed2025 ACC/AHA/ACEP/NAEMSP/SCAI Guideline for the ...

Major early complications include recurrent ischemia, heart failure, cardiogenic shock, brady- and tachyarrhythmias, acute mitral regurgitation from papillary muscle dysfunction or rupture, ventricular septal rupture, free-wall rupture, and pericarditis.BMJ+2BMJNon-ST-elevation myocardial infarctionPubMedReview of Current Management of Myocardial InfarctionPubMedAcute ST-Segment Elevation Myocardial Infarction (STEMI) Mechanical complications may present with abrupt hemodynamic deterioration, pulmonary edema, a new murmur, or tamponade physiology; transthoracic echocardiography is central to rapid evaluation.PubMedPubMedReview of Current Management of Myocardial Infarction

Cardiogenic shock after MI remains high risk. In the cited review, 30-day mortality is approximately 30% and one-year mortality approximately 50%; immediate angiography and infarct-related artery revascularization are emphasized, with mechanical circulatory support considered for refractory shock in selected patients.PubMedPubMedReview of Current Management of Myocardial Infarction

STEMI systems should enable prompt ECG acquisition, early catheterization laboratory activation, and coordinated transfer to PCI-capable centers. Quality-improvement initiatives using standardized pathways, feedback, and multidisciplinary coordination have improved evidence-based process measures in MI care.JAMA+1JAMAImproving Quality of Care for Acute Myocardial InfarctionPubMedEffect of implementing an acute myocardial infarction guideline on quality indicators - PMC

For NSTE-ACS, standardized serial-troponin pathways and explicit risk assessment can reduce diagnostic variation, but any algorithm must remain subordinate to clinical judgment in patients with high pretest probability, evolving ECG findings, or ongoing ischemia.BMJ+1BMJNon-ST-elevation myocardial infarctionNatureMachine learning for diagnosis of myocardial infarction using cardiac troponin concentrations | Nature Medicine